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Image of rare blue comet captured by the European Southern Observatory – Digital Trends

This image shows the Oort cloud comet C/2016 R2 (PANSTARRS). ESO / SPECULOOS Team / E. Jehin.

Last year, astronomers in Paris noticed a beautiful and distinctive comet, technically called C/2016 R2 but more colloquially known as the blue comet for its unusual hue. Now, the European Southern Observatory (ESO) has released this new image showing the comet up close.

C/2016 R2 is believed to originate from the Oort Cloud, a distant region of our solar system with objects orbiting the sun that are far beyond even the Kuiper Belt. The cloud consists of billions or even trillions of objects which form a sphere all around our sun, unlike the planets and the Kuiper Belt which form more of a flat disk shape around the sun. This means that the comet has a highly eccentric orbit, being titled at an angle of 58 degrees.

But the far more unusual feature of the comet is its color. Comets and their tails are typically yellow or neutral in shade, due to the way radiation from the sun is scattered by dust. This comet, however, has rare compounds in its coma, or the halo around its core. These compounds include carbon monoxide and nitrogen ions, which give the comet its blue color.

The comas and tails are formed when the comet comes close to the sun. Comets are balls of dust, ice, gas, and rock, the ESO scientists explained in a statement. When they pass close to the sun, their ice warms up, turns to gas, and escapes in a process called outgassing. This process forms fuzzy envelopes around the comets nucleus, called comas, and distinctive tails.

Its rare for a comet such as this to be observed, however. The blue comet circles the sun once every 20,000 years and we dont often see others like it. Comet C/2016 R2 is representative of a family of comets that we observe only rarely each century, the scientists said.

There are two theories for the origin of the comet: Either it is from a rare group of comets from beyond the line at which nitrogen can condense into solid grains. Or it could be a fragment that was knocked off a larger object orbiting beyond Neptune.

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Image of rare blue comet captured by the European Southern Observatory - Digital Trends

Sports Kansas City Comets sign 3-year deal to stay in Independence 41 Action News Staff – KSHB

KANSAS CITY, Mo. Two Kansas City-area sports teams on opposite sides of the metro made announcements about their future Tuesday.

The Kansas City Comets, of the Major Arena Soccer League, announced a three-year agreement to play at Silverstein Eye Center Arena in Independence, Missouri.

Since a revival in 2010, the Comets have played their home games in Independence. Theyll kick off the 10th season in Independence on Nov. 30 against the St. Louis Ambush.

We are thrilled to announce Silverstein Eye Centers Arena through 2022, Comets managing partner Brian Budzinski said in a release. We couldnt be more excited for our fans to see all the upgrades.

Earlier Tuesday , a new ownership group announced plans to buy the Kansas City T-Bones, keeping the team at Village West Stadium in Kansas City, Kansas. The deal still requires final approval.

Original post:

Sports Kansas City Comets sign 3-year deal to stay in Independence 41 Action News Staff - KSHB

comet | Definition, Composition, & Facts | Britannica.com

HistoryAncient Greece to the 19th century

The Greek philosopher Aristotle thought that comets were dry exhalations of Earth that caught fire high in the atmosphere or similar exhalations of the planets and stars. However, the Roman philosopher Seneca thought that comets were like the planets, though in much larger orbits. He wrote:

The man will come one day who will explain in what regions the comets move, why they diverge so much from the other stars, what is their size and their nature.

Aristotles view won out and persisted until 1577, when Danish astronomer Tycho Brahe attempted to use parallax to triangulate the distance to a bright comet. Because he could not measure any parallax, Brahe concluded that the comet was very far away, at least four times farther than the Moon.

Brahes student, German astronomer Johannes Kepler, devised his three laws of planetary motion using Brahes meticulous observations of Mars but was unable to fit his theory to the very eccentric orbits of comets. Kepler believed that comets traveled in straight lines through the solar system. The solution came from English scientist Isaac Newton, who used his new law of gravity to calculate a parabolic orbit for the comet of 1680. A parabolic orbit is open, with an eccentricity of exactly 1, meaning the comet would never return. (A circular orbit has an eccentricity of 0.) Any less-eccentric orbits are closed ellipses, which means a comet would return.

Newton was friends with English astronomer Edmond Halley, who used Newtons methods to determine the orbits for 24 observed comets, which he published in 1705. All the orbits were fit with parabolas because the quality of the observations at that time was not good enough to determine elliptical or hyperbolic orbits (eccentricities greater than 1). But Halley noted that the comets of 1531, 1607, and 1682 had remarkably similar orbits and had appeared at approximately 76-year intervals. He suggested that it was really one comet in an approximately 76-year orbit that returned at regular intervals. Halley predicted that the comet would return again in 1758. He did not live to see his prediction come true, but the comet was recovered on Christmas Day, 1758, and passed closest to the Sun on March 13, 1759. The comet was the first recognized periodic comet and was named in Halleys honour, Comet Halley.

Halley also speculated whether comets were members of the solar system or not. Although he could only calculate parabolic orbits, he suggested that the orbits were actually eccentric and closed, writing:

For so their Number will be determinate and, perhaps, not so very great. Besides, the Space between the Sun and the fixd Stars is so immense that there is Room enough for a Comet to revolve tho the period of its Revolution be vastly long.

The German astronomer Johann Encke was the second person to recognize a periodic comet. He determined that a comet discovered by French astronomer Jean-Louis Pons in 1818 did not seem to follow a parabolic orbit. He found that the orbit was indeed a closed ellipse. Moreover, he showed that the orbital period of the comet around the Sun was only 3.3 years, still the shortest orbital period of any comet on record. Encke also showed that the same comet had been observed by French astronomer Pierre Mchain in 1786, by British astronomer Caroline Herschel in 1795, and by Pons in 1805. The comet was named in Enckes honour, as Comet Halley was named for the astronomer who described its orbit.

Enckes Comet soon presented a new problem for astronomers. Because it returned so often, its orbit could be predicted precisely based on Newtons law of gravity, with effects from gravitational perturbations by the planets taken into account. But Enckes Comet repeatedly arrived about 2.5 hours too soon. Its orbit was slowly shrinking. The problem became even more complex when it was discovered that other periodic comets arrived too late. Those include the comets 6P/DArrest, 14P/Wolf 1, and even 1P/Halley, which typically returns about four days later than a purely gravitational orbit would predict.

Several explanations were suggested for this phenomenon, such as a resisting interplanetary medium that caused the comet to slowly lose orbital energy. However, that idea could not explain comets whose orbits were growing, not shrinking. German mathematician and astronomer Friedrich Bessel suggested that expulsion of material from a comet near perihelion was acting like a rocket motor and propelling the comet into a slightly shorter- (or longer-) period orbit each time it passed close to the Sun. History would prove Bessel right.

As the quality of the observations and mathematical techniques to calculate orbits improved, it became obvious that most comets were on elliptical orbits and thus were members of the solar system. Many were recognized to be periodic. But some orbit solutions for long-period comets suggested that they were slightly hyperbolic, suggesting that they came from interstellar space. That problem would not be solved until the 20th century.

Another interesting problem for astronomers was a comet discovered in 1826 by the Austrian military officer and astronomer Wilhelm, Freiherr (baron) von Biela. Calculation of its orbit showed that it, like Enckes Comet, was a short-period comet; it had a period of about 6.75 years. It was only the third periodic comet to be confirmed. It was identified with a comet observed by French astronomers Jacques Lebaix Montaigne and Charles Messier in 1772 and by Pons in 1805, and it returned, as predicted, in 1832. In 1839 the comet was too close in the sky to the Sun and could not be observed, but it was seen again on schedule in November 1845. On January 13, 1846, American astronomer Matthew Maury found that there was no longer a single comet: there were two, following each other closely around the Sun. The comets returned as a pair in 1852 but were never seen again. Searches for the comets in 1865 and 1872 were unsuccessful, but a brilliant meteor shower appeared in 1872 coming from the same direction from which the comets should have appeared. Astronomers concluded that the meteor shower was the debris of the disrupted comets. However, they were still left with the question as to why the comet broke up. That recurring meteor shower is now known as the Andromedids, named for the constellation in the sky where it appears to radiate from, but is also sometimes referred to as the Bielids.

The study of meteor showers received a huge boost on November 12 and 13, 1833, when observers saw an incredible meteor shower, with rates of hundreds and perhaps thousands of meteors per hour. That shower was the Leonids, so named because its radiant (or origin) is in the constellation Leo. It was suggested that Earth was encountering interplanetary debris spread along the Earth-crossing orbits of yet unknown bodies in the solar system. Further analysis showed that the orbits of the debris were highly eccentric.

American mathematician Hubert Newton published a series of papers in the 1860s in which he examined historical records of major Leonid meteor showers and found that they occurred about every 33 years. That showed that the Leonid particles were not uniformly spread around the orbit. He predicted another major shower for November 1866. As predicted, a large Leonid meteor storm occurred on November 13, 1866. In the same year, Italian astronomer Giovanni Schiaparelli computed the orbit of the Perseid meteor shower, usually observed on August 1012 each year, and noted its strong similarity to the orbit of Comet Swift-Tuttle (109P/1862 O1) discovered in 1862. Soon after, the Leonids were shown to have an orbit very similar to Comet Tempel-Tuttle (55P/1865 Y1), discovered in 1865. Since then the parent comets of many meteoroid streams have been identified, though the parent comets of some streams remains a mystery.

Meanwhile, the study of comets benefitted greatly from the improvement in the quality and size of telescopes and the technology for observing comets. In 1858 English portrait artist William Usherwood took the first photograph of a comet, Comet Donati (C/1858 L1), followed by American astronomer George Bond the next night. The first photographic discovery of a comet was made by American astronomer Edward Barnard in 1892, while he was photographing the Milky Way. The comet, which was in a short-period orbit, was known as D/Barnard 3 because it was soon lost, but it was recovered by Italian astronomer Andrea Boattini in 2008 and is now known as Comet Barnard/Boattini (206P/2008 T3). In 1864 Italian astronomer Giovanni Donati was the first to look at a comet through a spectroscope, and he discovered three broad emission bands that are now known to be caused by long-chain carbon molecules in the coma. The first spectrogram (a spectrum recorded on film) was of Comet Tebbutt (C/1881 K1), taken by English astronomer William Huggins on June 24, 1881. Later the same night, an American doctor and amateur astronomer, Henry Draper, took spectra of the same comet. Both men later became professional astronomers.

Some years before the appearance of Comet Halley in 1910, the molecule cyanogen was identified as one of the molecules in the spectra of cometary comae. Cyanogen is a poisonous gas derived from hydrogen cyanide (HCN), a well-known deadly poison. It was also detected in Halleys coma as that comet approached the Sun in 1910. That led to great consternation as Earth was predicted to pass through the tail of the comet. People panicked, bought comet pills, and threw end-of-the-world parties. But when the comet passed by only 0.15 AU away on the night of May 1819, 1910, there were no detectable effects.

The 20th century saw continued progress in cometary science. Spectroscopy revealed many of the molecules, radicals, and ions in the comae and tails of comets. An understanding began to develop about the nature of cometary tails, with the ion (Type I) tails resulting from the interaction of ionized molecules with some form of corpuscular radiation, possibly electrons and protons, from the Sun, and the dust (Type II) tails coming from solar radiation pressure on the fine dust particles emitted from the comet.

Astronomers continued to ask, Where do the comets come from? There were three schools of thought: (1) that comets were captured from interstellar space, (2) that comets were erupted out of the giant planets, or (3) that comets were primeval matter that had not been incorporated into the planets. The first idea had been suggested by French mathematician and astronomer Pierre Laplace in 1813, while the second came from another French mathematician-astronomer, Joseph Lagrange. The third came from English astronomer George Chambers in 1910.

The idea of an interstellar origin for comets ran into some serious problems. First, astronomers showed that capture of an interstellar comet by Jupiter, the most massive planet, was a highly unlikely event and probably could not account for the number of short-period comets then known. Also, no comets had ever been observed on truly hyperbolic orbits. Some long-period comets did have orbit solutions that were slightly hyperbolic, barely above an eccentricity of 1.0. But a truly hyperbolic comet approaching the solar system with the Suns velocity relative to the nearby stars of about 20 km (12 miles) per second would have an eccentricity of 2.0.

In 1914 Swedish-born Danish astronomer Elis Strmgren published a special list of cometary orbits. Strmgren took the well-determined orbits of long-period comets and projected them backward in time to before the comets had entered the planetary region. He then referenced the orbits to the barycentre (the centre of mass) of the entire solar system. He found that most of the apparently hyperbolic orbits became elliptical. That proved that the comets were members of the solar system. Orbits of that type are referred to as original orbits, whereas the orbit of a comet as it passes through the planetary region is called the osculating (or instantaneous) orbit, and the orbit after the comet has left the planetary region is called the future orbit.

The idea of comets erupting from giant planets was favoured by the Soviet astronomer Sergey Vsekhsvyatsky based on similar molecules having been discovered in both the atmospheres of the giant planets and in cometary comae. The idea helped to explain the many short-period comets that regularly encountered Jupiter. But the giant planets have very large escape velocities, about 60 km (37 miles) per second in the case of Jupiter, and it was difficult to understand what physical process could achieve those velocities. So Vsekhsvyatsky moved the origin sites to the satellites of the giant planets, which had far lower escape velocities. However, most scientists still did not believe in the eruption model. The discovery of volcanos on Jupiters large satellite Io by the Voyager 1 spacecraft in 1979 briefly resurrected the idea, but Ios composition proved to be a very poor match to the composition of comets.

Another idea about cometary origins was promoted by the English astronomer Raymond Lyttleton in a research paper in 1951 and a book, The Comets and Their Origin, in 1953. Because it was known that some comets were associated with meteor showers observed on Earth, the sandbank model suggested that a comet was simply a cloud of meteoritic particles held together by its own gravity. Interplanetary gases were adsorbed on the surfaces of the dust grains and escaped when the comet came close to the Sun and the particles were heated. Lyttleton went on to explain that comets were formed when the Sun and solar system passed through an interstellar dust cloud. The Suns gravity focused the passing dust in its wake, and these subclouds then collapsed under their own gravity to form the cometary sandbanks.

One problem with that theory was that Lyttleton estimated that the gravitational focusing by the Sun would bring the particles together only about 150 AU behind the Sun and solar system. But that did not agree well with the known orbits of long-period comets, which showed no concentration of comets that would have formed at that distance or in that direction. In addition, the total amount of gases that could be adsorbed on a sandbank cloud was not sufficient to explain the measured gas production rates of many observed comets.

In 1948 Dutch astronomer Adrianus van Woerkom, as part of his Ph.D. thesis work at the University of Leiden, examined the role of Jupiters gravity in changing the orbits of comets as they passed through the planetary system. He showed that Jupiter could scatter the orbits in energy, leading to either longer or shorter orbital periods and correspondingly to larger or smaller orbits. In some cases the gravitational perturbations from Jupiter were sufficient to change the previously elliptical orbits of the comets to hyperbolic, ejecting them from the solar system and sending them into interstellar space. Van Woerkom also showed that because of Jupiter, repeated passages of comets through the solar system would lead to a uniform distribution in orbital energy for the long-period comets, with as many long-period comets ending in very long-period orbits as in very short-period orbits. Finally, van Woerkom showed that Jupiter would eventually eject all the long-period comets to interstellar space over a time span of about one million years. Thus, the comets needed to be resupplied somehow.

Van Woerkoms thesis adviser was the Dutch astronomer Jan Oort, who had become famous in the 1920s for his work on the structure and rotation of the Milky Way Galaxy. Oort became interested in the problem of where the long-period comets came from. Building on van Woerkoms work, Oort closely examined the energy distribution of long-period comet original orbits as determined by Strmgren. He found that, as van Woerkom had predicted, there was a uniform distribution of orbital energies for most energy values. But, surprisingly, there was also a large excess of comets with orbital semimajor axes (half of the long axis of the comets elliptical orbit) larger than 20,000 AU.

Oort suggested that the excess of orbits at very large distances could only be explained if the long-period comets came from there. He proposed that the solar system was surrounded by a vast cloud of comets that stretched halfway to the nearest stars. He showed that gravitational perturbations by random passing stars would perturb the orbits in the comet cloud, occasionally sending a comet into the planetary region where it could be observed. Oort referred to those comets making their first passage through the planetary region as new comets. As the new comets pass through the planetary region, Jupiters gravity takes control of their orbits, spreading them in orbital energy, and either capturing them to shorter periods or ejecting them to interstellar space.

Based on the number of comets seen each year, Oort estimated that the cloud contained 190 billion comets; today that number is thought to be closer to one trillion comets. Oorts hypothesis was all the more impressive because it was based on accurate original orbits for only 19 comets. In his honour, the cloud of comets surrounding the solar system is called the Oort cloud.

Oort noticed that the number of long-period comets returning to the planetary system was far less than what his model predicted. To account for that, he suggested that the comets were physically lost by disruption (as had happened to Bielas Comet). Oort proposed two values for the disruption rate of comets on each perihelion passage, 0.3 and 1.9 percent, which both gave reasonably good results when comparing his predictions with the actual energy distribution, except for an excess of new comets at near-zero energy.

In 1979 American astronomer Paul Weissman (the author of this article) published computer simulations of the Oort cloud energy distribution using planetary perturbations by Jupiter and Saturn and physical models of loss mechanisms such as random disruption and formation of a nonvolatile crust, based on actual observations of comets. He showed that a very good agreement with the observed energy distribution could be obtained if new comets were disrupted about 10 percent of the time on the first perihelion passage from the Oort cloud and about 4 percent of the time on subsequent passages. Also, comet nuclei developed nonvolatile crusts, cutting off all coma activity, after about 10100 returns, on average.

In 1981 American astronomer Jack Hills suggested that in addition to the Oort cloud there was also an inner cloud extending inward toward the planetary region to about 1,000 AU from the Sun. Comets are not seen coming from this region because their orbits are too tightly bound to the Sun; stellar perturbations are typically not strong enough to change their orbits significantly. Hills hypothesized that only if a star came very close, even penetrating through the Oort cloud, could it excite the orbits of the comets in the inner cloud, sending a shower of comets into the planetary system.

But where did the Oort cloud come from? At large distances on the order of 104105 AU from the Sun, the solar nebula would have been too thin to form large bodies like comets that are several kilometres in diameter. The comets had to have formed much closer to the planetary region. Oort suggested that the comets were thrown out of the asteroid belt by close encounters with Jupiter. At that time it was not known that most asteroids are rocky, carbonaceous, or iron bodies and that only a fraction contain any water.

Oorts work was preceded in part by that of the Estonian astronomer Ernst pik. In 1932 pik published a paper examining what happened to meteors or comets scattered to very large distances from the Sun, where they could be perturbed by random passing stars. He showed that the gravitational tugs from the stars would raise the perihelion distances of most objects to beyond the most distant planet. Thus, he predicted that there would be a cloud of comets surrounding the solar system. However, pik said little about the comets returning to the planetary region, other than that some comets could be thrown into the Sun by the stars during their evolution outward to the cloud. Indeed, pik concluded:

comets of an aphelion distance exceeding 10,000 a.u., are not very likely to occur among the observable objects, because of the rapid increase of the average perihelion distance due to stellar perturbations.

pik also failed to make any comparison between his results and the known original orbits of the long-period comets.

Oorts paper, published in 1950, revolutionized the field of cometary dynamics. Two months later a paper on the nature of the cometary nucleus by Fred Whipple would do the same for cometary physics. Whipple combined many of the ideas of the day and suggested that the cometary nucleus was a solid body made up of volatile ices and meteoritic material. That was called the icy conglomerate model but also became more popularly known as the dirty snowball.

Whipple provided proof for his model in the form of the shrinking orbit of Enckes Comet. Whipple believed that, as Bessel had suggested, rocket forces from sublimating ices on the sunlit side of the nucleus would alter the comets orbit. For a nonrotating solid nucleus, the force would push the nucleus away from the Sun, appearing to lessen the effect of gravity. But if the comet nucleus was rotating (as most solar system bodies do) and if the rotation pole was not perpendicular to the plane of the comets orbit, both tangential forces (forward or backward along the comets direction of motion) and out-of-plane forces (up or down) could result. The effect was helped by the thermal lag caused by the Sun continuing to heat the nucleus surface after local noontime, just as temperatures on Earth are usually at their maximum a few hours after local noon.

Thus, Whipple explained the slow shrinking of Enckes orbit as the result of tangential forces that were pointed opposite to the comets direction of motion, causing the comet nucleus to slow down, slowly shrinking the orbit. That model also explained periodic comets whose orbits were growing, such as DArrest and Wolf 1, depending on the direction of the nucleis rotation poles and the direction in which the nuclei were rotating. Because the rocket force results from the high activity of the comet nucleus near perihelion, the force does not change the perihelion distance but rather the aphelion distance, either raising or lowering it.

Whipple also pointed out that the loss of cometary ices would leave a layer of nonvolatile material on the surface of the nucleus, making sublimation more difficult, as the heat from the Sun needed to filter down through multiple layers to where there were fresh ices. Furthermore, Whipple suggested that the solar systems zodiacal dust cloud came from dust released by comets as they passed through the planetary system.

Whipples ideas set off an intense debate over whether the nucleus was a solid body or not. Many scientists still advocated Lyttletons idea of a sandbank nucleus, simply a cloud of meteoritic material with adsorbed gases. The question would not be put definitively to rest until the first spacecraft encounters with Halleys Comet in 1986.

Solid proof for Whipples nongravitational force model came from English astronomer Brian Marsden, a colleague of Whipples at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. Marsden was an expert on comet and asteroid orbits and tested Whipples icy conglomerate model against the orbits of many known comets. Using a computer program that determined the orbits of comets and asteroids from observations, Marsden added a term for the expected rocket effect when the comet was active. In this he was aided by Belgian astronomer Armand Delsemme, who carefully calculated the rate of water ice sublimation as a function of a comets distance from the Sun.

When one calculates an orbit for an object, the calculation usually does not fit all the observed positions of the object perfectly. Small errors creep into the observed positions for many reasons, such as not knowing the exact time of the observations or finding the positions using an out-of-date star catalog. So every orbit fit has a mean residual, which is the average difference between the observations and the comets predicted position based on the newly determined orbit. Mean residuals of less than about 1.5 arc seconds are considered a good fit.

When Marsden calculated the comet orbits, he found that he could obtain smaller mean residuals if he included the rocket force in his calculations. Marsden found that for a short-period comet, the magnitude of the rocket force was typically only a few hundred-thousandths of the solar gravitational attraction, but that was enough to change the time when the comet would return. Later, Marsden and colleagues computed the rocket forces for long-period comets and found that there too the mean residuals were reduced. For the long-period comets, the rocket force was typically a few ten-thousandths of the solar gravitational attraction. Long-period comets tend to be far more active than short-period comets, and thus for them the force is larger.

A further interesting result of Marsdens work was that when he performed his calculations on apparently hyperbolic comet orbits, the resulting eccentricities often changed from hyperbolic to elliptical. Very few comets were left with hyperbolic original orbits, and all of those were only slightly hyperbolic. Marsden had provided further proof that all long-period comets were members of the solar system.

In 1951 the Dutch American astronomer Gerard Kuiper published an important paper on where the comets had formed. Kuiper was studying the origin of the solar system and suggested that the volatile molecules, radicals, and ions observed in cometary comae and tails (e.g., CH, NH, OH, CN, CO+, CO2+, N2+) must come from ices frozen in the solid nucleus (e.g., CH4, NH3, H2O, HCN, CO, CO2, and N2). But those ices could only condense in the solar nebula where it was very cold. So he suggested that comets had formed at 3850 AU from the Sun, where mean temperatures were only about 3045 K (243 to 228 C, or 406 to 379 F).

Kuiper suggested that the solar nebula did not end at the orbit of what was then considered the most distant planet, Pluto, at about 39 AU, but that it continued on to about 50 AU. He believed that at those large distances from the Sun neither the density of solar nebula material nor the time was enough to form another planet. Rather, he suggested that there would be a belt of smaller bodiesi.e., cometsbetween 38 and 50 AU. He also suggested that Pluto would dynamically eject comets from that region to distant orbits, forming the Oort cloud.

Astronomers have since discovered that Pluto is too small to have done that job (or even to be considered a planet), and it is really Neptune at 30 AU that defines the outer boundary of the planetary system. Neptune is large enough to slowly scatter comets both inward to short-period orbits and outward to the Oort cloud, along with some help from the other giant planets.

Kuipers 1951 paper did not achieve the same fame as those by Oort and Whipple in 1950, but astronomers occasionally followed up his ideas. In 1968 Egyptian astronomer Salah Hamid worked with Whipple and Marsden to study the orbits of seven comets that passed near the region of Kuipers hypothetical comet belt beyond Neptune. They found no evidence of gravitational perturbations from the belt and set upper limits on the mass of the belt of 0.5 Earth masses out to 40 AU and 1.3 Earth masses out to 50 AU.

The situation changed in 1980 when Uruguayan astronomer Julio Fernndez suggested that a comet belt beyond Neptune would be a good source for the short-period comets. Up until that time it was thought that short-period comets were long-period comets from the Oort cloud that had dynamically evolved to short-period orbits because of planetary perturbations, primarily by Jupiter. But astronomers who tried to simulate that process on computers found that it was very inefficient and likely could not supply new short-period comets fast enough to replace the existing ones that either were disrupted, faded away, or were perturbed out of the planetary region.

Fernndez recognized that a key element in understanding the short-period comets was their relatively low-inclination orbits. Typical short-period comets have orbital inclinations up to about 35, whereas long-period comets have completely random orbital inclinations from 0 to 180. Fernndez suggested that the easiest way to produce a low-inclination short-period comet population was to start with a source that had a relatively low inclination. Kuipers hypothesized comet belt beyond Neptune fit this requirement. Fernndez used dynamical simulations to show how comets could be perturbed by larger bodies in the comet belt, on the order of the size of Ceres, the largest asteroid (diameter of about 940 km [580 miles]), and be sent into orbits that could encounter Neptune. Neptune then could pass about half of the comets inward to Uranus, with the other half being sent outward to the Oort cloud. In that manner, comets could be handed down to each giant planet and finally to Jupiter, which placed the comets in short-period orbits.

Fernndezs paper renewed interest in a possible comet belt beyond Neptune. In 1988 American astronomer Martin Duncan and Canadian astronomers Thomas Quinn and Scott Tremaine built a more complex computer simulation of the trans-Neptunian comet belt and again showed that it was the likely source of the short-period comets. They also proposed that the belt be named in honour of Gerard Kuiper, based on the predictions of his 1951 paper. As fate would have it, the distant comet belt had also been predicted in two lesser-known papers in 1943 and 1949 by a retired Irish army officer and astronomer, Kenneth Edgeworth. Therefore, some scientists refer to the comet belt as the Kuiper belt, while others call it the Edgeworth-Kuiper belt.

Astronomers at observatories began to search for the distant objects. In 1992 they were finally rewarded when British astronomer David Jewitt and Vietnamese American astronomer Jane Luu found an object well beyond Neptune in an orbit with a semimajor axis of 43.9 AU, an eccentricity of only 0.0678, and an inclination of only 2.19. The object, officially designated (15760) 1992 QB1, has a diameter of about 200 km (120 miles). Since 1992 more than 1,500 objects have been found in the Kuiper belt, some almost as large as Pluto. In fact, it was the discovery of that swarm of bodies beyond Neptune that led to Pluto being recognized in 2006 as simply one of the largest bodies in the swarm and no longer a planet. (The same thing happened to the largest asteroid Ceres in the mid-19th century when it was recognized as simply the largest body in the asteroid belt and not a true planet.)

In 1977 American astronomer Charles Kowal discovered an unusual object orbiting the Sun among the giant planets. Named 2060 Chiron, it is about 200 km (120 miles) in diameter and has a low-inclination orbit that stretches from 8.3 AU (inside the orbit of Saturn) to 18.85 AU (just inside the orbit of Uranus). Because it can make close approaches to those two giant planets, the orbit is unstable on a time span of several million years. Thus, Chiron likely came from somewhere else. Even more interesting, several years later Chiron began to display a cometary coma even though it was still very far from the Sun. Chiron is one of a few objects that appear in both asteroid and comet catalogs; in the latter it is designated 95 P/Chiron.

Chiron was the first of a new class of objects in giant-planet-crossing orbits to be discovered. The searches for Kuiper belt objects have also led to the discovery of many similar objects orbiting the Sun among the giant planets. Collectively they are now known as the Centaur objects. About 300 such objects have now been found, and more than a few also show sporadic cometary activity.

The Centaurs appear to be objects that are slowly diffusing into the planetary region from the Kuiper belt. Some will eventually be seen as short-period comets, while most others will be thrown into long-period orbits or even ejected to interstellar space.

In 1996 European astronomers Eric Elst and Guido Pizarro found a new comet, which was designated 133P/Elst-Pizarro. But when the orbit of the comet was determined, it was found to lie in the outer asteroid belt with a semimajor axis of 3.16 AU, an eccentricity of 0.162, and an inclination of only 1.39. A search of older records showed that 133P had been observed previously in 1979 as an inactive asteroid. So it is another object that was catalogued as both a comet and an asteroid.

The explanation for 133P was that, given its position in the asteroid belt, where maximum solar surface temperatures are only about 48 C (54 F), it likely acquired some water in the form of ice from the solar nebula. Like in comets, the ices near the surface of 133P sublimated early in its history, leaving an insulating layer of nonvolatile material covering the ice at depth. Then a random impact from a piece of asteroidal debris punched through the insulating layer and exposed the buried ice. Comet 133P has shown regular activity at the same location in its orbit for at least three orbits since it was discovered.

Twelve additional objects in asteroidal orbits have been discovered since that time, most of them also in the outer main belt. They are sometimes referred to as main belt comets, though the more recently accepted term is active asteroids.

The latter half of the 20th century saw a massive leap forward in the understanding of the solar system as a result of spacecraft visits to the planets and their satellites. Those spacecraft collected a wealth of scientific data close up and in situ. The anticipated return of Halleys Comet in 1986 provided substantial motivation to begin using spacecraft to study comets.

The first comet mission (of a sort) was the International Cometary Explorer (ICE) spacecrafts encounter with Comet 21P/Giacobini-Zinner on September 11, 1985. The mission had originally been launched as part of a joint project by the U.S. National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) known as the International Sun-Earth Explorer (ISEE). The mission consisted of three spacecraft, two of them, ISEE-1 and -2, in Earth orbit and the third, ISEE-3, positioned in a heliocentric orbit between Earth and the Sun, studying the solar wind in Earths vicinity.

In 1982 and 1983 engineers maneuvered ISEE-3 to accomplish several gravity-assist encounters with the Moon, which put it on a trajectory to encounter 21P/Giacobini-Zinner. The spacecraft was targeted to pass through the ion tail of the comet, about 7,800 km (4,800 miles) behind the nucleus at a relative velocity of 21 km (13 miles) per second, and returned the first in situ measurements of the magnetic field, plasma, and energetic particle environment inside a comets tail. Those measurements confirmed the model of the comets ion tail first put forward in 1957 by the Swedish physicist (and later Nobel Prize winner) Hannes Alfvn. It also showed that H2O+ was the most common ion in the plasma tail, consistent with the Whipple model of an icy conglomerate nucleus. However, ICE carried no instruments to study the nucleus or coma of the comet.

In 1986 five spacecraft were sent to encounter Halleys Comet. They were informally known as the Halley Armada and consisted of two Japanese spacecraft, Suisei and Sakigake (Japanese for comet and pioneer, respectively); two Soviet spacecraft, Vega 1 and 2 (a contraction of Venus-Halley using Cyrillic spelling); and an ESA spacecraft, Giotto (named after the Italian painter who depicted the Star of Bethlehem as a comet in a fresco painted in 130506).

Suisei flew by Halley on March 8, 1986, at a distance of 151,000 km (94,000 miles) on the sunward side and produced ultraviolet images of the comets hydrogen corona, an extension of the visible coma seen only in ultraviolet light. It also measured the energetic particle environment in the solar wind ahead of the comet. Sakigakes closest approach to the comet was on March 11, 1986, at a distance of 6.99 million km (4.34 million miles), and it made additional measurements of the solar wind.

Before flying past Halleys Comet, the two Soviet spacecraft had flown by Venus and had each dropped off landers and balloons to study that planet. Vega 1 flew through the Halley coma on March 6, 1986, to within 8,889 km (5,523 miles) of the nucleus and made numerous measurements of the coma gas and dust composition, plasma and energetic particles, and magnetic field environment. It also returned the first picture ever of a solid cometary nucleus. Unfortunately, the camera was slightly out of focus and had other technical problems that required considerable image processing to see the nucleus. Vega 2 fared much better when it flew through the Halley coma on March 9 to within 8,030 km (4,990 miles) of the nucleus, and its images clearly showed a peanut-shaped nucleus about 16 by 8 km (10 by 5 miles) in diameter. The nucleus was also very dark, reflecting only about 4 percent of the incident sunlight, which had already been established from Earth-based observations.

Both Vega spacecraft carried infrared spectrometers designed to measure the temperature of the Halley nucleus. They found quite warm temperatures between 320 and 400 K (47 and 127 C [116 and 260 F]). That surprised many scientists who had predicted that the effect of water ice sublimation would be to cool the nucleuss surface; water ice requires a great deal of heat to sublimate. The high temperatures suggested that much of the nucleuss surface was not sublimating, but why?

Whipples classic paper in 1950 had suggested that as comets lost material from the surface, some particles were too heavy to escape the weak gravity of the nucleus and fell back onto the surface, forming a lag deposit. That idea was later studied by American astronomer and author David Brin in his thesis work with his adviser, Sri Lankan physicist Asoka Mendis, in 1979. As the lag deposit built up, it would effectively insulate the icy materials below it from sunlight. Calculations showed that a layer only 10100 cm (439 inches) in thickness could completely turn off sublimation from the surface. Brin and Mendis predicted that Halley would be so active that it would blow away any lag deposit, but that was not the case. Only about 30 percent of Halleys sunlit hemisphere was active. Bright dust jets could be seen coming from specific areas on the nucleus surface, but much of the surface showed no visible activity.

Giotto flew through Halleys coma on March 14, 1986, and passed only 596 km (370 miles) from the nucleus. It returned the highest-resolution images of the nucleus and showed a very rugged terrain with mountain peaks jutting up hundreds of metres from the surface. It also showed the same peanut shape that Vega 2 saw but from a different viewing angle and with much greater visible detail. Discrete dust jets were coming off the nucleus surface, but the resolution was not good enough to reveal the source of the jets.

Giotto and both Vega spacecraft obtained numerous measurements of the dust and gas in the coma. Dust particles came in two types: silicate and organic. The silicate grains were typical of rocks found on Earth such as forsterite (Mg2SiO4), a high-temperature mineralthat is, one which would be among the first to condense out of the hot solar nebula. Analyses of other grains showed that the comet was far richer in magnesium relative to iron. The organic grains were composed solely of the elements carbon, hydrogen, oxygen, and nitrogen and were called CHON grains based on the chemical symbol for each of those elements. Larger grains were also detected that were combinations of silicate and CHON grains, supporting the view that comet nuclei had accreted from the slow aggregation of tiny particles in the solar nebula.

The three spacecraft also measured gases in the coma, water being the dominant molecule but also carbon monoxide accounting for about 7 percent of the gas relative to water. Formaldehyde, carbon dioxide, and hydrogen cyanide were also detected at a few percent relative to water.

The Halley Armada was a rousing success and resulted from international cooperation by many nations. Its success is even more impressive when one considers that the spacecraft all flew by the Halley nucleus at velocities ranging from 68 to 79 km per second (152,000 to 177,000 miles per hour). (The velocities were so high because Halleys retrograde orbit had it going around the Sun in the opposite direction from the spacecraft.)

Giotto was later retargeted using assists from Earths gravity to pass within about 200 km (120 miles) of the nucleus of the comet 26P/Grigg-Skjellrup. The flyby was successful, but some of the scientific instruments, including the camera, were no longer working after being sandblasted at Halley.

The next comet mission was not until 1998, when NASA launched Deep Space 1, a spacecraft designed to test a variety of new technologies. After flying past the asteroid 9969 Braille in 1999, Deep Space 1 was retargeted to fly past the comet 19P/Borrelly on September 22, 2001. Images of the Borrelly nucleus showed it to be shaped like a bowling pin, with very rugged terrain on parts of its surface and mesa-like formations over a large area of it. Individual dust and gas jets were seen emanating from the surface, but the activity was far less than that of Halleys Comet.

The NASA Stardust mission was launched in 1999 with the goal of collecting samples of dust from the coma of Comet 81P/Wild 2. At a flyby speed of 6.1 km per second (13,600 miles per hour), the dust samples would be completely destroyed by impact with a hard collector. Therefore, Stardust used a material made of silica (sand) called aerogel that had a very low density, approaching that of air. The idea was that the aerogel would slow the dust particles without destroying them, much as a detective might shoot a bullet into a box full of cotton in order to collect the undamaged bullet. It worked, and thousands of fine dust particles were returned to Earth in 2006. Perhaps the biggest surprise was that the sample contained high-temperature materials that must have formed much closer to the Sun than where the comets formed in the outer solar system. That unexpected result meant that material in the solar nebula had been mixed, at least from the inside outward, during the formation of the planets.

Stardusts images of the nucleus of Wild 2 showed a surface that was radically different from either Halley or Borrelly. The surface appeared to be covered with large flat-floored depressions. Those were likely not impact craters, as they did not have the correct morphology and there were far too many large ones. There was some suggestion that it was a very new cometary surface on a nucleus that had not been close to the Sun before. Support for that was the fact that Wild 2 had been placed into its current orbit by a close Jupiter approach in 1974, reducing the perihelion distance to about 1.5 AU (224 million km, or 139 million miles). Before the Jupiter encounter, its perihelion was 4.9 AU (733 million km, or 455 million miles), beyond the region where water ice sublimation is significant.

In 2002 NASA launched a mission called Contour (Comet Nucleus Tour) that was to fly by Enckes Comet and 73P/Schwassman-Wachmann 3 and possibly continue on to 6P/DArrest. Unfortunately, the spacecraft structure failed when leaving Earth orbit.

In 2005 NASA launched yet another comet mission, called Deep Impact. It consisted of two spacecraft, a mother spacecraft that would fly by Comet 9P/Tempel 1 and a daughter spacecraft that would be deliberately crashed into the comet nucleus. The mother spacecraft would take images of the impact. The daughter spacecraft contained its own camera system to image the nucleus surface up to the moment of impact. To maximize the effect of the impact, the daughter spacecraft contained 360 kg (794 pounds) of solid copper. The predicted impact energy was equivalent to 4.8 tonnes of TNT.

The two spacecraft encountered Tempel 1 on July 4, 2005. The impactor produced the highest-resolution pictures of a nucleus surface ever, imaging details less than 10 metres (33 feet) in size. The mother spacecraft watched the explosion and saw a huge cloud of dust and gas emitted from the nucleus. One of the mission goals was to image the crater made by the explosion, but the dust cloud was so thick that the nucleus surface could not be seen through it. Because the mission was a flyby, the mother spacecraft could not wait around for the dust to clear.

Images of the Tempel 1 nucleus were very different from what had been seen before. The surface appeared to be old, with examples of geologic processes having occurred. There was evidence of dust flows across the nucleus surface and what appeared to be two modest-sized impact craters. There was evidence of material having been eroded away. For the first time, icy patches were discovered in some small areas of the nucleus surface.

For the first time, a mission was also able to measure the mass and density of a cometary nucleus. Typically, the nuclei are too small and their gravity too weak to affect the trajectory of the flyby spacecraft. The same was true for Tempel 1, but observations of the expanding dust cloud from the impact could be modeled so as to solve for the nucleus gravity. When combined with the volume of the nucleus as obtained from the camera images, it was shown that the Tempel 1 nucleus had a bulk density between 0.2 and 1.0 gram per cubic centimetre with a preferred value of 0.4 gram per cubic centimetre, less than half that of water ice. The measurement clearly confirmed ideas from telescopic research that comets were not very dense.

After the great success of Stardust and Deep Impact, NASA had additional plans for the spacecraft. Stardust was retargeted to go to Tempel 1 and image the crater from the Deep Impact explosion as well as more of the nucleus surface not seen on the first flyby. Deep Impact was retargeted to fly past 103P/Hartley 2, a small but very active comet.

Deep Impact, in its postimpact EPOXI mission, flew past Comet Hartley 2 on November 4, 2010. It imaged a small nucleus about 2.3 km (1.4 miles) in length and 0.9 km (0.6 mile) wide. As with Halley and Borrelly, the nucleus appeared to be two bodies stuck together, each having rough terrain but covered with very fine, smooth material at the neck where they came together. The most amazing result was that the smaller of the two bodies making up the nucleus was far more active than the larger one. The activity on the smaller body appeared to be driven by CO2 sublimationan unexpected result, given that short-period comets are expected to lose their near-surface CO2 early during their many passages close to the Sun. The other half of the nucleus was far less active and only showed evidence of water ice sublimation. The active half of the comet also appeared to be flinging baseball- to basketball-sized chunks of water ice into the coma, further enhancing the gas production from the comet as they sublimated away.

The EPOXI images also showed that the nucleus was not rotating smoothly but was in complex rotationa state where the comet nucleus rotates but the direction of the rotation pole precesses rapidly, drawing a large circle on the sky. Hartley 2 was the first encountered comet to exhibit complex rotation. It was likely driven by the very high activity from the smaller half of the nucleus, putting large torques on the nucleus rotation.

Stardust/NExT (New Exploration of Tempel 1) flew past Tempel 1 on February 14, 2011, and it imaged the spot where the Deep Impact daughter spacecraft had struck the nucleus. Some scientists believed that they saw evidence of a crater about 150 metres (500 feet) in diameter, but other scientists looked at the same images and saw no clear evidence of a crater. Some of the ambiguity was due to the fact that the Stardust camera was not as sharp as the Deep Impact cameras, and some of it was also due to the fact that sunlight was illuminating the nucleus from a different direction. The debate over whether there was a recognizable crater lingers on.

Among the new areas observed by Stardust-NeXT there was further evidence of geologic processes, including layered terrains. Using stereographic imaging, the scientists traced dust jets observed in the coma back to the nucleus surface, and they appeared to originate from some of the layered terrain. Again, the resolution of the images was not good enough to understand why the jets were coming from that area.

In 2004 ESA launched Rosetta (named after the Rosetta Stone, which had unlocked the secret of Egyptian hieroglyphics) on a trajectory to Comet 67P/Churyumov-Gerasimenko (67P). Rendezvous with 67P took place on August 6, 2014. Along the way, Rosetta successfully flew by the asteroids 2849 Steins and 21 Lutetia and obtained considerable scientific data. Rosetta uses 11 scientific instruments to study the nucleus, coma, and solar wind interaction. Unlike previous comet missions, Rosetta will orbit the nucleus until December 2015, providing a complete view of the comet as activity begins, reaches a maximum at perihelion, and then wanes. Rosetta carried a spacecraft called Philae that landed on the nucleus surface on November 12, 2014. Philae drilled into the nucleus surface to collect samples of the nucleus and analyze them in situ. As the first mission to orbit and land on a cometary nucleus, Rosetta is expected to answer many questions about the sources of cometary activity.

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comet | Definition, Composition, & Facts | Britannica.com

In Depth | Comets Solar System Exploration: NASA Science

OverviewIn the distant past, people were both awed and alarmed by comets, perceiving them as long-haired stars that appeared in the sky unannounced and unpredictably. Chinese astronomers kept extensive records for centuries, including illustrations of characteristic types of comet tails, times of cometary appearances and disappearances, and celestial positions. These historic comet annals have proven to be a valuable resource for later astronomers.

We now know that comets are leftovers from the dawn of our solar system around 4.6 billion years ago, and consist mostly of ice coated with dark organic material. They have been referred to as "dirty snowballs." They may yield important clues about the formation of our solar system. Comets may have brought water and organic compounds, the building blocks of life, to the early Earth and other parts of the solar system.

Where Do Comets Come From?

As theorized by astronomer Gerard Kuiper in 1951, a disc-like belt of icy bodies exists beyond Neptune, where a population of dark comets orbits the Sun in the realm of Pluto. These icy objects, occasionally pushed by gravity into orbits bringing them closer to the Sun, become the so-called short-period comets. Taking less than 200 years to orbit the Sun, in many cases their appearance is predictable because they have passed by before. Less predictable are long-period comets, many of which arrive from a region called the Oort Cloud about 100,000 astronomical units (that is, about 100,000 times the distance between Earth and the Sun) from the Sun. These Oort Cloud comets can take as long as 30 million years to complete one trip around the Sun.

Each comet has a tiny frozen part, called a nucleus, often no larger than a few kilometers across. The nucleus contains icy chunks, frozen gases with bits of embedded dust. A comet warms up as it nears the Sun and develops an atmosphere, or coma. The Sun's heat causes the comet's ices to change to gases so the coma gets larger. The coma may extend hundreds of thousands of kilometers. The pressure of sunlight and high-speed solar particles (solar wind) can blow the coma dust and gas away from the Sun, sometimes forming a long, bright tail. Comets actually have two tailsa dust tail and an ion (gas) tail.

Most comets travel a safe distance from the Suncomet Halley comes no closer than 89 million kilometers (55 million miles). However, some comets, called sungrazers, crash straight into the Sun or get so close that they break up and evaporate.

Exploration of Comets

Scientists have long wanted to study comets in some detail, tantalized by the few 1986 images of comet Halley's nucleus. NASA's Deep Space 1 spacecraft flew by comet Borrelly in 2001 and photographed its nucleus, which is about 8 kilometers (5 miles) long.

NASA's Stardust mission successfully flew within 236 kilometers (147 miles) of the nucleus of Comet Wild 2 in January 2004, collecting cometary particles and interstellar dust for a sample return to Earth in 2006. The photographs taken during this close flyby of a comet nucleus show jets of dust and a rugged, textured surface. Analysis of the Stardust samples suggests that comets may be more complex than originally thought. Minerals formed near the Sun or other stars were found in the samples, suggesting that materials from the inner regions of the solar system traveled to the outer regions where comets formed.

Another NASA mission, Deep Impact, consisted of a flyby spacecraft and an impactor. In July 2005, the impactor was released into the path of the nucleus of comet Tempel 1 in a planned collision, which vaporized the impactor and ejected massive amounts of fine, powdery material from beneath the comet's surface. En route to impact, the impactor camera imaged the comet in increasing detail. Two cameras and a spectrometer on the flyby spacecraft recorded the dramatic excavation that helped determine the interior composition and structure of the nucleus.

After their successful primary missions, the Deep Impact spacecraft and the Stardust spacecraft were still healthy and were retargeted for additional cometary flybys. Deep Impact's mission, EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation), comprised two projects: the Deep Impact Extended Investigation (DIXI), which encountered comet Hartley 2 in November 2010, and the Extrasolar Planet Observation and Characterization (EPOCh) investigation, which searched for Earth-size planets around other stars on route to Hartley 2. NASA returned to comet Tempel 1 in 2011, when the Stardust New Exploration of Tempel 1 (NExT) mission observed changes in the nucleus since Deep Impact's 2005 encounter.

How Comets Get Their Names

Comet naming can be complicated. Comets are generally named for their discoverereither a person or a spacecraft. This International Astronomical Union guideline was developed only in the last century. For example, comet Shoemaker-Levy 9 was so named because it was the ninth short-periodic comet discovered by Eugene and Carolyn Shoemaker and David Levy. Since spacecraft are very effective at spotting comets many comets have LINEAR, SOHO or WISE in their names.

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In Depth | Comets Solar System Exploration: NASA Science

Overview | Comets Solar System Exploration: NASA Science

Comets are cosmic snowballs of frozen gases, rock and dust that orbit the Sun. When frozen, they are the size of a small town. When a comet's orbit brings it close to the Sun, it heats up and spews dust and gases into a giant glowing head larger than most planets. The dust and gases form a tail that stretches away from the Sun for millions of miles. There are likely billions of comets orbiting our Sun in the Kuiper Belt and even more distant Oort Cloud.

The current number of known comets is:

Go farther. Explore Comets in Depth

Key Science Targets

Kid-Friendly Comets

Kid-Friendly Comets

Comets orbit the Sun just like planets and asteroids do, except a comet usually has a very elongated orbit.

As the comet gets closer to the Sun, some of the ice starts to melt and boil off, along with particles of dust. These particles and gases make a cloud around the nucleus, called a coma.

The coma is lit by the Sun. The sunlight also pushes this material into the beautiful brightly lit tail of the comet.

Visit NASA Space Place for more kid-friendly facts.

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Overview | Comets Solar System Exploration: NASA Science

Comet Facts – Comets – Astronomy for Kids

Temperature is very irregular in outer space. The parts that are near stars are extremely hot! Think about Venus, the second closest planet to the Sun. It goes up to 462C. But the background temperature in space is about -270C super cold! Things can change states if temperatures change so much. They can go from solid, to liquid, to gas! This is actually the reason why comets have their tails!

The tail is one of the most distinctive features of a comet!

Comets may look small from a distance, but theyre actually gigantic!

See how the Kuiper belt is disc-shaped? The Oort Cloud is farther away, so gravity from the planets dont affect it as much. Thats why it envelopes the Solar System like a sphere or a cloud!

Where the comet moves in space is important for its shape! When comets are still in the far reaches of the Oort Cloud or the Kuiper Belt, theyre made up only of their nuclei. But everything changes once they move closer to the Sun! Remember a comet is mostly made out of ice.

And what happens to ice as it gets close to heat? It melts! In the case of comets, their nuclei start to sublimate, changing from ice to gas immediately. This is when the comet starts developing its other parts!

As the ice melts, the comet gains a coma. The coma is basically a giant cloud of dust and different gases that surrounds the nucleus. Comas are extremely big up to 600,000 miles across! The coma and the nucleus make up the head of the comet. A hydrogen cloud also develops around the comets head, but we cant see it with our eyes. Hydrogen clouds are even bigger than comas they can get as big as 10 Suns!

Heres an easyway to remember what a comets head is called. The coma looks kind of like the head of a comma without its tail!

The comets tail appears when it gets close to the Sun. The tail is probably the most special feature of comets!

Asteroids are not icy like comets. Instead, theyre made out of rock and metals

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Comet Facts - Comets - Astronomy for Kids

Halley’s Comet – Wikipedia

Halley was the first comet to be recognized as periodic. Until the Renaissance, the philosophical consensus on the nature of comets, promoted by Aristotle, was that they were disturbances in Earth's atmosphere. This idea was disproved in 1577 by Tycho Brahe, who used parallax measurements to show that comets must lie beyond the Moon. Many were still unconvinced that comets orbited the Sun, and assumed instead that they must follow straight paths through the Solar System.[20]

In 1687, Sir Isaac Newton published his Philosophi Naturalis Principia Mathematica, in which he outlined his laws of gravity and motion. His work on comets was decidedly incomplete. Although he had suspected that two comets that had appeared in succession in 1680 and 1681 were the same comet before and after passing behind the Sun (he was later found to be correct; see Newton's Comet),[21] he was unable to completely reconcile comets into his model.

Ultimately, it was Newton's friend, editor and publisher, Edmond Halley, who, in his 1705 Synopsis of the Astronomy of Comets, used Newton's new laws to calculate the gravitational effects of Jupiter and Saturn on cometary orbits.[22] Having compiled a list of 24 comet observations, he calculated that the orbital elements of a second comet that had appeared in 1682 were nearly the same as those of two comets that had appeared in 1531 (observed by Petrus Apianus) and 1607 (observed by Johannes Kepler).[22][23] Halley thus concluded that all three comets were, in fact, the same object returning about every 76 years, a period that has since been found to vary between 7479 years. After a rough estimate of the perturbations the comet would sustain from the gravitational attraction of the planets, he predicted its return for 1758.[24] While he had personally observed the comet around perihelion in September 1682,[25] Halley died in 1742 before he could observe its predicted return.[26]

Halley's prediction of the comet's return proved to be correct, although it was not seen until 25 December 1758, by Johann Georg Palitzsch, a German farmer and amateur astronomer. It did not pass through its perihelion until 13 March 1759, the attraction of Jupiter and Saturn having caused a retardation of 618 days.[27] This effect was computed prior to its return (with a one-month error to 13 April)[28] by a team of three French mathematicians, Alexis Clairaut, Joseph Lalande, and Nicole-Reine Lepaute.[29] The confirmation of the comet's return was the first time anything other than planets had been shown to orbit the Sun. It was also one of the earliest successful tests of Newtonian physics, and a clear demonstration of its explanatory power.[30] The comet was first named in Halley's honour by French astronomer Nicolas Louis de Lacaille in 1759.[30]

Some scholars have proposed that first-century Mesopotamian astronomers already had recognized Halley's Comet as periodic.[31] This theory notes a passage in the Bavli Talmud[32] that refers to "a star which appears once in seventy years that makes the captains of the ships err."[33]

Researchers in 1981 attempting to calculate the past orbits of Halley by numerical integration starting from accurate observations in the seventeenth and eighteenth centuries could not produce accurate results further back than 837 due to a close approach to Earth in that year. It was necessary to use ancient Chinese comet observations to constrain their calculations.[34]

Halley's orbital period has varied between 7479 years since 240 BC.[30][11] Its orbit around the Sun is highly elliptical, with an orbital eccentricity of 0.967 (with 0 being a circle and 1 being a parabolic trajectory). The perihelion, the point in the comet's orbit when it is nearest the Sun, is just 0.6 AU.[35] This is between the orbits of Mercury and Venus. Its aphelion, or farthest distance from the Sun, is 35 AU (roughly the distance of Pluto). Unusual for an object in the Solar System, Halley's orbit is retrograde; it orbits the Sun in the opposite direction to the planets, or, clockwise from above the Sun's north pole. The orbit is inclined by 18 to the ecliptic, with much of it lying south of the ecliptic. (Because it is retrograde, the true inclination is 162.)[36] Due to the retrograde orbit, it has one of the highest velocities relative to the Earth of any object in the Solar System. The 1910 passage was at a relative velocity of 70.56km/s (157,838mph or 254,016km/h).[37] Because its orbit comes close to Earth's in two places, Halley is associated with two meteor showers: the Eta Aquariids in early May, and the Orionids in late October.[38] Halley is the parent body to the Orionids. Observations conducted around the time of Halley's appearance in 1986 suggested that the comet could additionally perturb the Eta Aquarid meteor shower, although it might not be the parent of that shower.[39]

Halley is classified as a periodic or short-period comet; one with an orbit lasting 200 years or less.[40] This contrasts it with long-period comets, whose orbits last for thousands of years. Periodic comets have an average inclination to the ecliptic of only ten degrees, and an orbital period of just 6.5 years, so Halley's orbit is atypical.[30] Most short-period comets (those with orbital periods shorter than 20 years and inclinations of 2030 degrees or less) are called Jupiter-family comets. Those resembling Halley, with orbital periods of between 20 and 200 years and inclinations extending from zero to more than 90 degrees, are called Halley-type comets.[40][41] As of 2015[update], only 75 Halley-type comets have been observed, compared with 511 identified Jupiter family comets.[42]

The orbits of the Halley-type comets suggest that they were originally long-period comets whose orbits were perturbed by the gravity of the giant planets and directed into the inner Solar System.[40] If Halley was once a long-period comet, it is likely to have originated in the Oort Cloud,[41] a sphere of cometary bodies that has an inner edge of 20,00050,000 AU. Conversely the Jupiter-family comets are generally believed to originate in the Kuiper belt,[41] a flat disc of icy debris between 30 AU (Neptune's orbit) and 50 AU from the Sun (in the scattered disc). Another point of origin for the Halley-type comets was proposed in 2008, when a trans-Neptunian object with a retrograde orbit similar to Halley's was discovered, 2008 KV42, whose orbit takes it from just outside that of Uranus to twice the distance of Pluto. It may be a member of a new population of small Solar System bodies that serves as the source of Halley-type comets.[43]

Halley has probably been in its current orbit for 16,000200,000 years, although it is not possible to numerically integrate its orbit for more than a few tens of apparitions, and close approaches before 837 AD can only be verified from recorded observations.[44] The non-gravitational effects can be crucial;[44] as Halley approaches the Sun, it expels jets of sublimating gas from its surface, which knock it very slightly off its orbital path. These orbital changes cause delays in its perihelion of four days, average.[45]

In 1989, Boris Chirikov and Vitaly Vecheslavov performed an analysis of 46 apparitions of Halley's Comet taken from historical records and computer simulations. These studies showed that its dynamics were chaotic and unpredictable on long timescales.[46] Halley's projected lifetime could be as long as 10million years. These studies also showed that many physical properties of Halley's Comet dynamics can be approximately described by a simple symplectic map, known as the Kepler map.[47] More recent work suggests that Halley will evaporate, or split in two, within the next few tens of thousands of years, or will be ejected from the Solar System within a few hundred thousand years.[48][41] Observations by D.W. Hughes suggest that Halley's nucleus has been reduced in mass by 8090% over the last 20003000 revolutions.[16]

The Giotto and Vega missions gave planetary scientists their first view of Halley's surface and structure. Like all comets, as Halley nears the Sun, its volatile compounds (those with low boiling points, such as water, carbon monoxide, carbon dioxide and other ices) begin to sublime from the surface of its nucleus.[49] This causes the comet to develop a coma, or atmosphere, up to 100,000km across.[3] Evaporation of this dirty ice releases dust particles, which travel with the gas away from the nucleus. Gas molecules in the coma absorb solar light and then re-radiate it at different wavelengths, a phenomenon known as fluorescence, whereas dust particles scatter the solar light. Both processes are responsible for making the coma visible.[13] As a fraction of the gas molecules in the coma are ionized by the solar ultraviolet radiation,[13] pressure from the solar wind, a stream of charged particles emitted by the Sun, pulls the coma's ions out into a long tail, which may extend more than 100millionkilometers into space.[49][50] Changes in the flow of the solar wind can cause disconnection events, in which the tail completely breaks off from the nucleus.[15]

Despite the vast size of its coma, Halley's nucleus is relatively small: barely 15kilometers long, 8kilometers wide and perhaps 8kilometers thick.[b] Its shape vaguely resembles that of a peanut.[3] Its mass is relatively low (roughly 2.21014kg)[4] and its average density is about 0.6g/cm3, indicating that it is made of a large number of small pieces, held together very loosely, forming a structure known as a rubble pile.[5] Ground-based observations of coma brightness suggested that Halley's rotation period was about 7.4 days. Images taken by the various spacecraft, along with observations of the jets and shell, suggested a period of 52hours.[16] Given the irregular shape of the nucleus, Halley's rotation is likely to be complex.[49] Although only 25% of Halley's surface was imaged in detail during the flyby missions, the images revealed an extremely varied topography, with hills, mountains, ridges, depressions, and at least one crater.[16]

Halley is the most active of all the periodic comets, with others, such as Comet Encke and Comet Holmes, being one or two orders of magnitude less active.[16] Its day side (the side facing the Sun) is far more active than the night side. Spacecraft observations showed that the gases ejected from the nucleus were 80% water vapour, 17% carbon monoxide and 34% carbon dioxide,[51] with traces of hydrocarbons[52] although more-recent sources give a value of 10% for carbon monoxide and also include traces of methane and ammonia.[53] The dust particles were found to be primarily a mixture of carbonhydrogenoxygennitrogen (CHON) compounds common in the outer Solar System, and silicates, such as are found in terrestrial rocks.[49] The dust particles decreased in size down to the limits of detection (~0.001m).[15] The ratio of deuterium to hydrogen in the water released by Halley was initially thought to be similar to that found in Earth's ocean water, suggesting that Halley-type comets may have delivered water to Earth in the distant past. Subsequent observations showed Halley's deuterium ratio to be far higher than that found in Earth's oceans, making such comets unlikely sources for Earth's water.[49]

Giotto provided the first evidence in support of Fred Whipple's "dirty snowball" hypothesis for comet construction; Whipple postulated that comets are icy objects warmed by the Sun as they approach the inner Solar System, causing ices on their surfaces to sublimate (change directly from a solid to a gas), and jets of volatile material to burst outward, creating the coma. Giotto showed that this model was broadly correct,[49] though with modifications. Halley's albedo, for instance, is about 4%, meaning that it reflects only 4% of the sunlight hitting it; about what one would expect for coal.[54] Thus, despite appearing brilliant white to observers on Earth, Halley's Comet is in fact pitch black. The surface temperature of evaporating "dirty ice" ranges from 170 K (103C) at higher albedo to 220K (53C) at low albedo; Vega 1 found Halley's surface temperature to be in the range 300400 K (30130C). This suggested that only 10% of Halley's surface was active, and that large portions of it were coated in a layer of dark dust that retained heat.[15] Together, these observations suggested that Halley was in fact predominantly composed of non-volatile materials, and thus more closely resembled a "snowy dirtball" than a "dirty snowball".[16][55]

Halley may have been recorded as early as 467BC, but this is uncertain. A comet was recorded in ancient Greece between 468 and 466 BC; its timing, location, duration, and associated meteor shower all suggest it was Halley.[56] According to Pliny the Elder, that same year a meteorite fell in the town of Aegospotami, in Thrace. He described it as brown in colour and the size of a wagon load.[57] Chinese chroniclers also mention a comet in that year.[58]

The first certain appearance of Halley's Comet in the historical record is a description from 240BC, in the Chinese chronicle Records of the Grand Historian or Shiji, which describes a comet that appeared in the east and moved north.[59] The only surviving record of the 164BC apparition is found on two fragmentary Babylonian tablets, now owned by the British Museum.[59]

The apparition of 87BC was recorded in Babylonian tablets which state that the comet was seen "day beyond day" for a month.[60] This appearance may be recalled in the representation of Tigranes the Great, an Armenian king who is depicted on coins with a crown that features, according to Vahe Gurzadyan and R. Vardanyan, "a star with a curved tail [that] may represent the passage of Halley's Comet in 87BC." Gurzadyan and Vardanyan argue that "Tigranes could have seen Halley's Comet when it passed closest to the Sun on August 6 in 87BC" as the comet would have been a "most recordable event"; for ancient Armenians it could have heralded the New Era of the brilliant King of Kings.[61]

The apparition of 12BC was recorded in the Book of Han by Chinese astronomers of the Han Dynasty who tracked it from August through October.[10] It passed within 0.16AU of Earth.[62] Halley's appearance in 12BC, only a few years distant from the conventionally assigned date of the birth of Jesus Christ, has led some theologians and astronomers to suggest that it might explain the biblical story of the Star of Bethlehem. There are other explanations for the phenomenon, such as planetary conjunctions, and there are also records of other comets that appeared closer to the date of Jesus' birth.[63]

If, as has been suggested, the reference in the Talmud to "a star which appears once in seventy years that makes the captains of the ships err"[64] (see above) refers to Halley's Comet, it may be a reference to the 66AD appearance, because this passage is attributed to the Rabbi Yehoshua ben Hananiah. This apparition was the only one to occur during ben Hananiah's lifetime.[65]

The 141AD apparition was recorded in Chinese chronicles.[66] It was also recorded in the Tamil work Purananuru, in connection with the death of the south Indian Chera king Yanaikatchai Mantaran Cheral Irumporai.[67]

The 374AD and 607 approaches each came within 0.09AU of Earth.[62] The 684AD apparition was recorded in Europe in one of the sources used by the compiler of the 1493 Nuremberg Chronicles; it is the oldest known picture of a comet. Chinese records also report it as the "broom star".[68][23]

In 837, Halley's Comet may have passed as close as 0.03AU (3.2million miles; 5.1million kilometers) from Earth, by far its closest approach.[62] Its tail may have stretched 60degrees across the sky. It was recorded by astronomers in China, Japan, Germany, the Byzantine Empire, and the Middle East.[10] In 912, Halley is recorded in the Annals of Ulster, which state "A dark and rainy year. A comet appeared."[69]

In 1066, the comet was seen in England and thought to be an omen: later that year Harold II of England died at the Battle of Hastings; it was a bad omen for Harold, but a good omen for the man who defeated him, William the Conqueror. The comet is represented on the Bayeux Tapestry and described in the tituli as a star. Surviving accounts from the period describe it as appearing to be four times the size of Venus and shining with a light equal to a quarter of that of the Moon. Halley came within 0.10AU of Earth at that time.[62]

This appearance of the comet is also noted in the Anglo-Saxon Chronicle. Eilmer of Malmesbury may have seen Halley previously in 989, as he wrote of it in 1066: "You've come, have you?... You've come, you source of tears to many mothers, you evil. I hate you! It is long since I saw you; but as I see you now you are much more terrible, for I see you brandishing the downfall of my country. I hate you!"[70]

The Irish Annals of the Four Masters recorded the comet as "A star [that] appeared on the seventh of the Calends of May, on Tuesday after Little Easter, than whose light the brilliance or light of The Moon was not greater; and it was visible to all in this manner till the end of four nights afterwards."[69] Chaco Native Americans in New Mexico may have recorded the 1066 apparition in their petroglyphs.[71]

The 1145 apparition was recorded by the monk Eadwine. The 1986 apparition exhibited a fan tail similar to Eadwine's drawing.[68] Some claim that Genghis Khan was inspired to turn his conquests toward Europe by the 1222 apparition.[72] The 1301 apparition may have been seen by the artist Giotto di Bondone, who represented the Star of Bethlehem as a fire-colored comet in the Nativity section of his Arena Chapel cycle, completed in 1305.[68] Its 1378 appearance is recorded in the Annales Mediolanenses[73] as well as in East Asian sources.[74]

In 1456, the year of Halley's next apparition, the Ottoman Empire invaded the Kingdom of Hungary, culminating in the Siege of Belgrade in July of that year. In a papal bull, Pope Calixtus III ordered special prayers be said for the city's protection. In 1470, the humanist scholar Bartolomeo Platina wrote in his Lives of the Popes that,[75]

A hairy and fiery star having then made its appearance for several days, the mathematicians declared that there would follow grievous pestilence, dearth and some great calamity. Calixtus, to avert the wrath of God, ordered supplications that if evils were impending for the human race He would turn all upon the Turks, the enemies of the Christian name. He likewise ordered, to move God by continual entreaty, that notice should be given by the bells to call the faithful at midday to aid by their prayers those engaged in battle with the Turk.

Platina's account is not mentioned in official records. In the 18th century, a Frenchman further embellished the story, in anger at the Church, by claiming that the Pope had "excommunicated" the comet, though this story was most likely his own invention.[76]

Halley's apparition of 1456 was also witnessed in Kashmir and depicted in great detail by rvara, a Sanskrit poet and biographer to the Sultans of Kashmir. He read the apparition as a cometary portent of doom foreshadowing the imminent fall of Sultan Zayn al-Abidin (AD 1418/14201470).[77]

After witnessing a bright light in the sky which most historians have identified as Halley's Comet, Zara Yaqob, Emperor of Ethiopia from 1434 to 1468, founded the city of Debre Berhan (tr. City of Light) and made it his capital for the remainder of his reign.[78]

Halley's periodic returns have been subject to scientific investigation since the 16th century. The three apparitions from 1531 to 1682 were noted by Edmond Halley, enabling him to predict its 1759 return.[79] Streams of vapour observed during the comet's 1835 apparition prompted astronomer Friedrich Wilhelm Bessel to propose that the jet forces of evaporating material could be great enough to significantly alter a comet's orbit.[80]

The 1910 approach, which came into naked-eye view around 10 April[62] and came to perihelion on 20 April,[62] was notable for several reasons: it was the first approach of which photographs exist, and the first for which spectroscopic data were obtained.[15] Furthermore, the comet made a relatively close approach of 0.15 AU,[62] making it a spectacular sight. Indeed, on 19 May, Earth actually passed through the tail of the comet.[81][82] One of the substances discovered in the tail by spectroscopic analysis was the toxic gas cyanogen,[83] which led astronomer Camille Flammarion to claim that, when Earth passed through the tail, the gas "would impregnate the atmosphere and possibly snuff out all life on the planet."[84] His pronouncement led to panicked buying of gas masks and quack "anti-comet pills" and "anti-comet umbrellas" by the public.[85] In reality, as other astronomers were quick to point out, the gas is so diffuse that the world suffered no ill effects from the passage through the tail.[84]

The comet added to the unrest in China on the eve of Xinhai Revolution that would end the last dynasty in 1911. As James Hutson, a missionary in Sichuan Province at the time, recorded,

The people believe that it indicates calamity such as war, fire, pestilence, and a change of dynasty. In some places on certain days the doors were unopened for half a day, no water was carried and many did not even drink water as it was rumoured that pestilential vapour was being poured down upon the earth from the comet."[86]

The 1910 visitation is also recorded as being the travelling companion of Hedley Churchward, the first known English Muslim to make the Haj pilgrimage to Mecca. However, his explanation of its scientific predictability did not meet with favour in the Holy City.[87]

The comet was also fertile ground for hoaxes. One that reached major newspapers claimed that the Sacred Followers, a supposed Oklahoma religious group, attempted to sacrifice a virgin to ward off the impending disaster, but were stopped by the police.[88]

American satirist and writer Mark Twain was born on 30 November 1835, exactly two weeks after the comet's perihelion. In his autobiography, published in 1909, he said,

I came in with Halley's comet in 1835. It is coming again next year, and I expect to go out with it. It will be the greatest disappointment of my life if I don't go out with Halley's comet. The Almighty has said, no doubt: 'Now here are these two unaccountable freaks; they came in together, they must go out together.'[89][90]

Twain died on 21 April 1910, the day following the comet's subsequent perihelion.[91] The 1985 fantasy film The Adventures of Mark Twain was inspired by the quotation.

Halley's 1910 apparition is distinct from the Great Daylight Comet of 1910, which surpassed Halley in brilliance and was actually visible in broad daylight for a short period, approximately four months before Halley made its appearance.[92][93]

Halley's 1986 apparition was the least favourable on record. The comet and Earth were on opposite sides of the Sun in February 1986, creating the worst viewing circumstances for Earth observers for the last 2,000 years.[94] Halley's closest approach was 0.42 AU.[95] Additionally, with increased light pollution from urbanization, many people failed to even see the comet. It was possible to observe it in areas outside of cities with the help of binoculars.[96] Further, the comet appeared brightest when it was almost invisible from the northern hemisphere in March and April.[97] Halley's approach was first detected by astronomers David Jewitt and G. Edward Danielson on 16 October 1982 using the 5.1m Hale telescope at Mount Palomar and a CCD camera.[98] The first person to visually observe the comet on its 1986 return was amateur astronomer Stephen James O'Meara on 24 January 1985. O'Meara used a home-built 24-inch telescope on top of Mauna Kea to detect the magnitude 19.6 comet.[99] On 8 November 1985, Stephen Edberg (then serving as the Coordinator for Amateur Observations at NASA's Jet Propulsion Laboratory) and Charles Morris were the first to observe Halley's Comet with the naked eye in its 1986 apparition.[100][101]

Although Halley's Comet's retrograde orbit and high inclination make it difficult to send a space probe to it,[102] the 1986 apparition gave scientists the opportunity to closely study the comet, and several probes were launched to do so. The Soviet Vega 1 started returning images of Halley on 4 March 1986, and the first ever of its nucleus,[16] and made its flyby on 6 March, followed by Vega 2 making its flyby on 9 March. On 14 March, the Giotto space probe, launched by the European Space Agency, made the closest pass of the comet's nucleus.[16] There were also two Japanese probes, Suisei and Sakigake. The probes were unofficially known as the Halley Armada.[103]

Based on data retrieved by Astron, the largest ultraviolet space telescope of the time, during its Halley's Comet observations in December 1985, a group of Soviet scientists developed a model of the comet's coma.[104] The comet was also observed from space by the International Cometary Explorer. Originally International Sun-Earth Explorer 3, the probe was renamed and freed from its L1 Lagrangian point location in Earth's orbit to intercept comets 21P/Giacobini-Zinner and Halley.[105]

Two Space Shuttle missions the ill-fated STS-51-L (ended by the Challenger disaster)[106] and STS-61-E were scheduled to observe Halley's Comet from low Earth orbit. STS-51-L carried the Shuttle-Pointed Tool for Astronomy (SPARTAN-203) satellite, also called the Halley's Comet Experiment Deployable (HCED).[107] STS-61-E was a Columbia mission scheduled for March 1986, carrying the ASTRO-1 platform to study the comet.[108] Due to the suspension of America's manned space program after the Challenger explosion, the mission was canceled, and ASTRO-1 would not fly until late 1990 on STS-35.[109]

On 12 February 1991, at a distance of 14.4AU (2.15109km) from the Sun, Halley displayed an outburst that lasted for several months, releasing a cloud of dust 300,000km across.[49] The outburst likely started in December 1990, and then the comet brightened from magnitude 24.3 to magnitude 18.9.[110] Halley was most recently observed in 2003 by three of the Very Large Telescopes at Paranal, Chile, when Halley's magnitude was 28.2. The telescopes observed Halley, at the faintest and farthest any comet has ever been imaged, in order to verify a method for finding very faint trans-Neptunian objects.[9] Astronomers are now able to observe the comet at any point in its orbit.[9]

The next predicted perihelion of Halley's Comet is 28 July 2061,[1] when it is expected to be better positioned for observation than during the 19851986 apparition, as it will be on the same side of the Sun as Earth.[11] It is expected to have an apparent magnitude of 0.3, compared with only +2.1 for the 1986 apparition.[111] It has been calculated that on 9 September 2060, Halley will pass within 0.98AU (147,000,000km) of Jupiter, and then on 20 August 2061 will pass within 0.0543AU (8,120,000km) of Venus.[112] In 2134, Halley is expected to pass within 0.09AU (13,000,000km) of Earth.[112] Its apparent magnitude is expected to be 2.0.[111]

Halley's calculations enabled the comet's earlier appearances to be found in the historical record. The following table sets out the astronomical designations for every apparition of Halley's Comet from 240BC, the earliest documented widespread sighting.[2][113] For example, "1P/1982U1, 1986III, 1982i" indicates that for the perihelion in 1986, Halley was the first period comet known (designated 1P) and this apparition was the first seen in half-month U (the second half of October)[114] in 1982 (giving 1P/1982 U1); it was the third comet past perihelion in 1986 (1986 III); and it was the ninth comet spotted in 1982 (provisional designation 1982i). The perihelion dates of each apparition are shown.[115] The perihelion dates farther from the present are approximate, mainly because of uncertainties in the modelling of non-gravitational effects. Perihelion dates of 1531 and earlier are in the Julian calendar, while perihelion dates 1607 and after are in the Gregorian calendar.[116]

Halley's Comet is visible from Earth every 7479 years.[2][10][11]

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Comet | astronomy | Britannica.com

HistoryAncient Greece to the 19th century

The Greek philosopher Aristotle thought that comets were dry exhalations of Earth that caught fire high in the atmosphere or similar exhalations of the planets and stars. However, the Roman philosopher Seneca thought that comets were like the planets, though in much larger orbits. He wrote:

The man will come one day who will explain in what regions the comets move, why they diverge so much from the other stars, what is their size and their nature.

Aristotles view won out and persisted until 1577, when Danish astronomer Tycho Brahe attempted to use parallax to triangulate the distance to a bright comet. Because he could not measure any parallax, Brahe concluded that the comet was very far away, at least four times farther than the Moon.

Brahes student, German astronomer Johannes Kepler, devised his three laws of planetary motion using Brahes meticulous observations of Mars but was unable to fit his theory to the very eccentric orbits of comets. Kepler believed that comets traveled in straight lines through the solar system. The solution came from English scientist Isaac Newton, who used his new law of gravity to calculate a parabolic orbit for the comet of 1680. A parabolic orbit is open, with an eccentricity of exactly 1, meaning the comet would never return. (A circular orbit has an eccentricity of 0.) Any less-eccentric orbits are closed ellipses, which means a comet would return.

Newton was friends with English astronomer Edmond Halley, who used Newtons methods to determine the orbits for 24 observed comets, which he published in 1705. All the orbits were fit with parabolas because the quality of the observations at that time was not good enough to determine elliptical or hyperbolic orbits (eccentricities greater than 1). But Halley noted that the comets of 1531, 1607, and 1682 had remarkably similar orbits and had appeared at approximately 76-year intervals. He suggested that it was really one comet in an approximately 76-year orbit that returned at regular intervals. Halley predicted that the comet would return again in 1758. He did not live to see his prediction come true, but the comet was recovered on Christmas Day, 1758, and passed closest to the Sun on March 13, 1759. The comet was the first recognized periodic comet and was named in Halleys honour, Comet Halley.

Halley also speculated whether comets were members of the solar system or not. Although he could only calculate parabolic orbits, he suggested that the orbits were actually eccentric and closed, writing:

For so their Number will be determinate and, perhaps, not so very great. Besides, the Space between the Sun and the fixd Stars is so immense that there is Room enough for a Comet to revolve tho the period of its Revolution be vastly long.

The German astronomer Johann Encke was the second person to recognize a periodic comet. He determined that a comet discovered by French astronomer Jean-Louis Pons in 1818 did not seem to follow a parabolic orbit. He found that the orbit was indeed a closed ellipse. Moreover, he showed that the orbital period of the comet around the Sun was only 3.3 years, still the shortest orbital period of any comet on record. Encke also showed that the same comet had been observed by French astronomer Pierre Mchain in 1786, by British astronomer Caroline Herschel in 1795, and by Pons in 1805. The comet was named in Enckes honour, as Comet Halley was named for the astronomer who described its orbit.

Enckes Comet soon presented a new problem for astronomers. Because it returned so often, its orbit could be predicted precisely based on Newtons law of gravity, with effects from gravitational perturbations by the planets taken into account. But Enckes Comet repeatedly arrived about 2.5 hours too soon. Its orbit was slowly shrinking. The problem became even more complex when it was discovered that other periodic comets arrived too late. Those include the comets 6P/DArrest, 14P/Wolf 1, and even 1P/Halley, which typically returns about four days later than a purely gravitational orbit would predict.

Several explanations were suggested for this phenomenon, such as a resisting interplanetary medium that caused the comet to slowly lose orbital energy. However, that idea could not explain comets whose orbits were growing, not shrinking. German mathematician and astronomer Friedrich Bessel suggested that expulsion of material from a comet near perihelion was acting like a rocket motor and propelling the comet into a slightly shorter- (or longer-) period orbit each time it passed close to the Sun. History would prove Bessel right.

As the quality of the observations and mathematical techniques to calculate orbits improved, it became obvious that most comets were on elliptical orbits and thus were members of the solar system. Many were recognized to be periodic. But some orbit solutions for long-period comets suggested that they were slightly hyperbolic, suggesting that they came from interstellar space. That problem would not be solved until the 20th century.

Another interesting problem for astronomers was a comet discovered in 1826 by the Austrian military officer and astronomer Wilhelm, Freiherr (baron) von Biela. Calculation of its orbit showed that it, like Enckes Comet, was a short-period comet; it had a period of about 6.75 years. It was only the third periodic comet to be confirmed. It was identified with a comet observed by French astronomers Jacques Lebaix Montaigne and Charles Messier in 1772 and by Pons in 1805, and it returned, as predicted, in 1832. In 1839 the comet was too close in the sky to the Sun and could not be observed, but it was seen again on schedule in November 1845. On January 13, 1846, American astronomer Matthew Maury found that there was no longer a single comet: there were two, following each other closely around the Sun. The comets returned as a pair in 1852 but were never seen again. Searches for the comets in 1865 and 1872 were unsuccessful, but a brilliant meteor shower appeared in 1872 coming from the same direction from which the comets should have appeared. Astronomers concluded that the meteor shower was the debris of the disrupted comets. However, they were still left with the question as to why the comet broke up. That recurring meteor shower is now known as the Andromedids, named for the constellation in the sky where it appears to radiate from, but is also sometimes referred to as the Bielids.

The study of meteor showers received a huge boost on November 12 and 13, 1833, when observers saw an incredible meteor shower, with rates of hundreds and perhaps thousands of meteors per hour. That shower was the Leonids, so named because its radiant (or origin) is in the constellation Leo. It was suggested that Earth was encountering interplanetary debris spread along the Earth-crossing orbits of yet unknown bodies in the solar system. Further analysis showed that the orbits of the debris were highly eccentric.

American mathematician Hubert Newton published a series of papers in the 1860s in which he examined historical records of major Leonid meteor showers and found that they occurred about every 33 years. That showed that the Leonid particles were not uniformly spread around the orbit. He predicted another major shower for November 1866. As predicted, a large Leonid meteor storm occurred on November 13, 1866. In the same year, Italian astronomer Giovanni Schiaparelli computed the orbit of the Perseid meteor shower, usually observed on August 1012 each year, and noted its strong similarity to the orbit of Comet Swift-Tuttle (109P/1862 O1) discovered in 1862. Soon after, the Leonids were shown to have an orbit very similar to Comet Tempel-Tuttle (55P/1865 Y1), discovered in 1865. Since then the parent comets of many meteoroid streams have been identified, though the parent comets of some streams remains a mystery.

Meanwhile, the study of comets benefitted greatly from the improvement in the quality and size of telescopes and the technology for observing comets. In 1858 English portrait artist William Usherwood took the first photograph of a comet, Comet Donati (C/1858 L1), followed by American astronomer George Bond the next night. The first photographic discovery of a comet was made by American astronomer Edward Barnard in 1892, while he was photographing the Milky Way. The comet, which was in a short-period orbit, was known as D/Barnard 3 because it was soon lost, but it was recovered by Italian astronomer Andrea Boattini in 2008 and is now known as Comet Barnard/Boattini (206P/2008 T3). In 1864 Italian astronomer Giovanni Donati was the first to look at a comet through a spectroscope, and he discovered three broad emission bands that are now known to be caused by long-chain carbon molecules in the coma. The first spectrogram (a spectrum recorded on film) was of Comet Tebbutt (C/1881 K1), taken by English astronomer William Huggins on June 24, 1881. Later the same night, an American doctor and amateur astronomer, Henry Draper, took spectra of the same comet. Both men later became professional astronomers.

Some years before the appearance of Comet Halley in 1910, the molecule cyanogen was identified as one of the molecules in the spectra of cometary comae. Cyanogen is a poisonous gas derived from hydrogen cyanide (HCN), a well-known deadly poison. It was also detected in Halleys coma as that comet approached the Sun in 1910. That led to great consternation as Earth was predicted to pass through the tail of the comet. People panicked, bought comet pills, and threw end-of-the-world parties. But when the comet passed by only 0.15 AU away on the night of May 1819, 1910, there were no detectable effects.

The 20th century saw continued progress in cometary science. Spectroscopy revealed many of the molecules, radicals, and ions in the comae and tails of comets. An understanding began to develop about the nature of cometary tails, with the ion (Type I) tails resulting from the interaction of ionized molecules with some form of corpuscular radiation, possibly electrons and protons, from the Sun, and the dust (Type II) tails coming from solar radiation pressure on the fine dust particles emitted from the comet.

Astronomers continued to ask, Where do the comets come from? There were three schools of thought: (1) that comets were captured from interstellar space, (2) that comets were erupted out of the giant planets, or (3) that comets were primeval matter that had not been incorporated into the planets. The first idea had been suggested by French mathematician and astronomer Pierre Laplace in 1813, while the second came from another French mathematician-astronomer, Joseph Lagrange. The third came from English astronomer George Chambers in 1910.

The idea of an interstellar origin for comets ran into some serious problems. First, astronomers showed that capture of an interstellar comet by Jupiter, the most massive planet, was a highly unlikely event and probably could not account for the number of short-period comets then known. Also, no comets had ever been observed on truly hyperbolic orbits. Some long-period comets did have orbit solutions that were slightly hyperbolic, barely above an eccentricity of 1.0. But a truly hyperbolic comet approaching the solar system with the Suns velocity relative to the nearby stars of about 20 km (12 miles) per second would have an eccentricity of 2.0.

In 1914 Swedish-born Danish astronomer Elis Strmgren published a special list of cometary orbits. Strmgren took the well-determined orbits of long-period comets and projected them backward in time to before the comets had entered the planetary region. He then referenced the orbits to the barycentre (the centre of mass) of the entire solar system. He found that most of the apparently hyperbolic orbits became elliptical. That proved that the comets were members of the solar system. Orbits of that type are referred to as original orbits, whereas the orbit of a comet as it passes through the planetary region is called the osculating (or instantaneous) orbit, and the orbit after the comet has left the planetary region is called the future orbit.

The idea of comets erupting from giant planets was favoured by the Soviet astronomer Sergey Vsekhsvyatsky based on similar molecules having been discovered in both the atmospheres of the giant planets and in cometary comae. The idea helped to explain the many short-period comets that regularly encountered Jupiter. But the giant planets have very large escape velocities, about 60 km (37 miles) per second in the case of Jupiter, and it was difficult to understand what physical process could achieve those velocities. So Vsekhsvyatsky moved the origin sites to the satellites of the giant planets, which had far lower escape velocities. However, most scientists still did not believe in the eruption model. The discovery of volcanos on Jupiters large satellite Io by the Voyager 1 spacecraft in 1979 briefly resurrected the idea, but Ios composition proved to be a very poor match to the composition of comets.

Another idea about cometary origins was promoted by the English astronomer Raymond Lyttleton in a research paper in 1951 and a book, The Comets and Their Origin, in 1953. Because it was known that some comets were associated with meteor showers observed on Earth, the sandbank model suggested that a comet was simply a cloud of meteoritic particles held together by its own gravity. Interplanetary gases were adsorbed on the surfaces of the dust grains and escaped when the comet came close to the Sun and the particles were heated. Lyttleton went on to explain that comets were formed when the Sun and solar system passed through an interstellar dust cloud. The Suns gravity focused the passing dust in its wake, and these subclouds then collapsed under their own gravity to form the cometary sandbanks.

One problem with that theory was that Lyttleton estimated that the gravitational focusing by the Sun would bring the particles together only about 150 AU behind the Sun and solar system. But that did not agree well with the known orbits of long-period comets, which showed no concentration of comets that would have formed at that distance or in that direction. In addition, the total amount of gases that could be adsorbed on a sandbank cloud was not sufficient to explain the measured gas production rates of many observed comets.

In 1948 Dutch astronomer Adrianus van Woerkom, as part of his Ph.D. thesis work at the University of Leiden, examined the role of Jupiters gravity in changing the orbits of comets as they passed through the planetary system. He showed that Jupiter could scatter the orbits in energy, leading to either longer or shorter orbital periods and correspondingly to larger or smaller orbits. In some cases the gravitational perturbations from Jupiter were sufficient to change the previously elliptical orbits of the comets to hyperbolic, ejecting them from the solar system and sending them into interstellar space. Van Woerkom also showed that because of Jupiter, repeated passages of comets through the solar system would lead to a uniform distribution in orbital energy for the long-period comets, with as many long-period comets ending in very long-period orbits as in very short-period orbits. Finally, van Woerkom showed that Jupiter would eventually eject all the long-period comets to interstellar space over a time span of about one million years. Thus, the comets needed to be resupplied somehow.

Van Woerkoms thesis adviser was the Dutch astronomer Jan Oort, who had become famous in the 1920s for his work on the structure and rotation of the Milky Way Galaxy. Oort became interested in the problem of where the long-period comets came from. Building on van Woerkoms work, Oort closely examined the energy distribution of long-period comet original orbits as determined by Strmgren. He found that, as van Woerkom had predicted, there was a uniform distribution of orbital energies for most energy values. But, surprisingly, there was also a large excess of comets with orbital semimajor axes (half of the long axis of the comets elliptical orbit) larger than 20,000 AU.

Oort suggested that the excess of orbits at very large distances could only be explained if the long-period comets came from there. He proposed that the solar system was surrounded by a vast cloud of comets that stretched halfway to the nearest stars. He showed that gravitational perturbations by random passing stars would perturb the orbits in the comet cloud, occasionally sending a comet into the planetary region where it could be observed. Oort referred to those comets making their first passage through the planetary region as new comets. As the new comets pass through the planetary region, Jupiters gravity takes control of their orbits, spreading them in orbital energy, and either capturing them to shorter periods or ejecting them to interstellar space.

Based on the number of comets seen each year, Oort estimated that the cloud contained 190 billion comets; today that number is thought to be closer to one trillion comets. Oorts hypothesis was all the more impressive because it was based on accurate original orbits for only 19 comets. In his honour, the cloud of comets surrounding the solar system is called the Oort cloud.

Oort noticed that the number of long-period comets returning to the planetary system was far less than what his model predicted. To account for that, he suggested that the comets were physically lost by disruption (as had happened to Bielas Comet). Oort proposed two values for the disruption rate of comets on each perihelion passage, 0.3 and 1.9 percent, which both gave reasonably good results when comparing his predictions with the actual energy distribution, except for an excess of new comets at near-zero energy.

In 1979 American astronomer Paul Weissman (the author of this article) published computer simulations of the Oort cloud energy distribution using planetary perturbations by Jupiter and Saturn and physical models of loss mechanisms such as random disruption and formation of a nonvolatile crust, based on actual observations of comets. He showed that a very good agreement with the observed energy distribution could be obtained if new comets were disrupted about 10 percent of the time on the first perihelion passage from the Oort cloud and about 4 percent of the time on subsequent passages. Also, comet nuclei developed nonvolatile crusts, cutting off all coma activity, after about 10100 returns, on average.

In 1981 American astronomer Jack Hills suggested that in addition to the Oort cloud there was also an inner cloud extending inward toward the planetary region to about 1,000 AU from the Sun. Comets are not seen coming from this region because their orbits are too tightly bound to the Sun; stellar perturbations are typically not strong enough to change their orbits significantly. Hills hypothesized that only if a star came very close, even penetrating through the Oort cloud, could it excite the orbits of the comets in the inner cloud, sending a shower of comets into the planetary system.

But where did the Oort cloud come from? At large distances on the order of 104105 AU from the Sun, the solar nebula would have been too thin to form large bodies like comets that are several kilometres in diameter. The comets had to have formed much closer to the planetary region. Oort suggested that the comets were thrown out of the asteroid belt by close encounters with Jupiter. At that time it was not known that most asteroids are rocky, carbonaceous, or iron bodies and that only a fraction contain any water.

Oorts work was preceded in part by that of the Estonian astronomer Ernst pik. In 1932 pik published a paper examining what happened to meteors or comets scattered to very large distances from the Sun, where they could be perturbed by random passing stars. He showed that the gravitational tugs from the stars would raise the perihelion distances of most objects to beyond the most distant planet. Thus, he predicted that there would be a cloud of comets surrounding the solar system. However, pik said little about the comets returning to the planetary region, other than that some comets could be thrown into the Sun by the stars during their evolution outward to the cloud. Indeed, pik concluded:

comets of an aphelion distance exceeding 10,000 a.u., are not very likely to occur among the observable objects, because of the rapid increase of the average perihelion distance due to stellar perturbations.

pik also failed to make any comparison between his results and the known original orbits of the long-period comets.

Oorts paper, published in 1950, revolutionized the field of cometary dynamics. Two months later a paper on the nature of the cometary nucleus by Fred Whipple would do the same for cometary physics. Whipple combined many of the ideas of the day and suggested that the cometary nucleus was a solid body made up of volatile ices and meteoritic material. That was called the icy conglomerate model but also became more popularly known as the dirty snowball.

Whipple provided proof for his model in the form of the shrinking orbit of Enckes Comet. Whipple believed that, as Bessel had suggested, rocket forces from sublimating ices on the sunlit side of the nucleus would alter the comets orbit. For a nonrotating solid nucleus, the force would push the nucleus away from the Sun, appearing to lessen the effect of gravity. But if the comet nucleus was rotating (as most solar system bodies do) and if the rotation pole was not perpendicular to the plane of the comets orbit, both tangential forces (forward or backward along the comets direction of motion) and out-of-plane forces (up or down) could result. The effect was helped by the thermal lag caused by the Sun continuing to heat the nucleus surface after local noontime, just as temperatures on Earth are usually at their maximum a few hours after local noon.

Thus, Whipple explained the slow shrinking of Enckes orbit as the result of tangential forces that were pointed opposite to the comets direction of motion, causing the comet nucleus to slow down, slowly shrinking the orbit. That model also explained periodic comets whose orbits were growing, such as DArrest and Wolf 1, depending on the direction of the nucleis rotation poles and the direction in which the nuclei were rotating. Because the rocket force results from the high activity of the comet nucleus near perihelion, the force does not change the perihelion distance but rather the aphelion distance, either raising or lowering it.

Whipple also pointed out that the loss of cometary ices would leave a layer of nonvolatile material on the surface of the nucleus, making sublimation more difficult, as the heat from the Sun needed to filter down through multiple layers to where there were fresh ices. Furthermore, Whipple suggested that the solar systems zodiacal dust cloud came from dust released by comets as they passed through the planetary system.

Whipples ideas set off an intense debate over whether the nucleus was a solid body or not. Many scientists still advocated Lyttletons idea of a sandbank nucleus, simply a cloud of meteoritic material with adsorbed gases. The question would not be put definitively to rest until the first spacecraft encounters with Halleys Comet in 1986.

Solid proof for Whipples nongravitational force model came from English astronomer Brian Marsden, a colleague of Whipples at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. Marsden was an expert on comet and asteroid orbits and tested Whipples icy conglomerate model against the orbits of many known comets. Using a computer program that determined the orbits of comets and asteroids from observations, Marsden added a term for the expected rocket effect when the comet was active. In this he was aided by Belgian astronomer Armand Delsemme, who carefully calculated the rate of water ice sublimation as a function of a comets distance from the Sun.

When one calculates an orbit for an object, the calculation usually does not fit all the observed positions of the object perfectly. Small errors creep into the observed positions for many reasons, such as not knowing the exact time of the observations or finding the positions using an out-of-date star catalog. So every orbit fit has a mean residual, which is the average difference between the observations and the comets predicted position based on the newly determined orbit. Mean residuals of less than about 1.5 arc seconds are considered a good fit.

When Marsden calculated the comet orbits, he found that he could obtain smaller mean residuals if he included the rocket force in his calculations. Marsden found that for a short-period comet, the magnitude of the rocket force was typically only a few hundred-thousandths of the solar gravitational attraction, but that was enough to change the time when the comet would return. Later, Marsden and colleagues computed the rocket forces for long-period comets and found that there too the mean residuals were reduced. For the long-period comets, the rocket force was typically a few ten-thousandths of the solar gravitational attraction. Long-period comets tend to be far more active than short-period comets, and thus for them the force is larger.

A further interesting result of Marsdens work was that when he performed his calculations on apparently hyperbolic comet orbits, the resulting eccentricities often changed from hyperbolic to elliptical. Very few comets were left with hyperbolic original orbits, and all of those were only slightly hyperbolic. Marsden had provided further proof that all long-period comets were members of the solar system.

In 1951 the Dutch American astronomer Gerard Kuiper published an important paper on where the comets had formed. Kuiper was studying the origin of the solar system and suggested that the volatile molecules, radicals, and ions observed in cometary comae and tails (e.g., CH, NH, OH, CN, CO+, CO2+, N2+) must come from ices frozen in the solid nucleus (e.g., CH4, NH3, H2O, HCN, CO, CO2, and N2). But those ices could only condense in the solar nebula where it was very cold. So he suggested that comets had formed at 3850 AU from the Sun, where mean temperatures were only about 3045 K (243 to 228 C, or 406 to 379 F).

Kuiper suggested that the solar nebula did not end at the orbit of what was then considered the most distant planet, Pluto, at about 39 AU, but that it continued on to about 50 AU. He believed that at those large distances from the Sun neither the density of solar nebula material nor the time was enough to form another planet. Rather, he suggested that there would be a belt of smaller bodiesi.e., cometsbetween 38 and 50 AU. He also suggested that Pluto would dynamically eject comets from that region to distant orbits, forming the Oort cloud.

Astronomers have since discovered that Pluto is too small to have done that job (or even to be considered a planet), and it is really Neptune at 30 AU that defines the outer boundary of the planetary system. Neptune is large enough to slowly scatter comets both inward to short-period orbits and outward to the Oort cloud, along with some help from the other giant planets.

Kuipers 1951 paper did not achieve the same fame as those by Oort and Whipple in 1950, but astronomers occasionally followed up his ideas. In 1968 Egyptian astronomer Salah Hamid worked with Whipple and Marsden to study the orbits of seven comets that passed near the region of Kuipers hypothetical comet belt beyond Neptune. They found no evidence of gravitational perturbations from the belt and set upper limits on the mass of the belt of 0.5 Earth masses out to 40 AU and 1.3 Earth masses out to 50 AU.

The situation changed in 1980 when Uruguayan astronomer Julio Fernndez suggested that a comet belt beyond Neptune would be a good source for the short-period comets. Up until that time it was thought that short-period comets were long-period comets from the Oort cloud that had dynamically evolved to short-period orbits because of planetary perturbations, primarily by Jupiter. But astronomers who tried to simulate that process on computers found that it was very inefficient and likely could not supply new short-period comets fast enough to replace the existing ones that either were disrupted, faded away, or were perturbed out of the planetary region.

Fernndez recognized that a key element in understanding the short-period comets was their relatively low-inclination orbits. Typical short-period comets have orbital inclinations up to about 35, whereas long-period comets have completely random orbital inclinations from 0 to 180. Fernndez suggested that the easiest way to produce a low-inclination short-period comet population was to start with a source that had a relatively low inclination. Kuipers hypothesized comet belt beyond Neptune fit this requirement. Fernndez used dynamical simulations to show how comets could be perturbed by larger bodies in the comet belt, on the order of the size of Ceres, the largest asteroid (diameter of about 940 km [580 miles]), and be sent into orbits that could encounter Neptune. Neptune then could pass about half of the comets inward to Uranus, with the other half being sent outward to the Oort cloud. In that manner, comets could be handed down to each giant planet and finally to Jupiter, which placed the comets in short-period orbits.

Fernndezs paper renewed interest in a possible comet belt beyond Neptune. In 1988 American astronomer Martin Duncan and Canadian astronomers Thomas Quinn and Scott Tremaine built a more complex computer simulation of the trans-Neptunian comet belt and again showed that it was the likely source of the short-period comets. They also proposed that the belt be named in honour of Gerard Kuiper, based on the predictions of his 1951 paper. As fate would have it, the distant comet belt had also been predicted in two lesser-known papers in 1943 and 1949 by a retired Irish army officer and astronomer, Kenneth Edgeworth. Therefore, some scientists refer to the comet belt as the Kuiper belt, while others call it the Edgeworth-Kuiper belt.

Astronomers at observatories began to search for the distant objects. In 1992 they were finally rewarded when British astronomer David Jewitt and Vietnamese American astronomer Jane Luu found an object well beyond Neptune in an orbit with a semimajor axis of 43.9 AU, an eccentricity of only 0.0678, and an inclination of only 2.19. The object, officially designated (15760) 1992 QB1, has a diameter of about 200 km (120 miles). Since 1992 more than 1,500 objects have been found in the Kuiper belt, some almost as large as Pluto. In fact, it was the discovery of that swarm of bodies beyond Neptune that led to Pluto being recognized in 2006 as simply one of the largest bodies in the swarm and no longer a planet. (The same thing happened to the largest asteroid Ceres in the mid-19th century when it was recognized as simply the largest body in the asteroid belt and not a true planet.)

In 1977 American astronomer Charles Kowal discovered an unusual object orbiting the Sun among the giant planets. Named 2060 Chiron, it is about 200 km (120 miles) in diameter and has a low-inclination orbit that stretches from 8.3 AU (inside the orbit of Saturn) to 18.85 AU (just inside the orbit of Uranus). Because it can make close approaches to those two giant planets, the orbit is unstable on a time span of several million years. Thus, Chiron likely came from somewhere else. Even more interesting, several years later Chiron began to display a cometary coma even though it was still very far from the Sun. Chiron is one of a few objects that appear in both asteroid and comet catalogs; in the latter it is designated 95 P/Chiron.

Chiron was the first of a new class of objects in giant-planet-crossing orbits to be discovered. The searches for Kuiper belt objects have also led to the discovery of many similar objects orbiting the Sun among the giant planets. Collectively they are now known as the Centaur objects. About 300 such objects have now been found, and more than a few also show sporadic cometary activity.

The Centaurs appear to be objects that are slowly diffusing into the planetary region from the Kuiper belt. Some will eventually be seen as short-period comets, while most others will be thrown into long-period orbits or even ejected to interstellar space.

In 1996 European astronomers Eric Elst and Guido Pizarro found a new comet, which was designated 133P/Elst-Pizarro. But when the orbit of the comet was determined, it was found to lie in the outer asteroid belt with a semimajor axis of 3.16 AU, an eccentricity of 0.162, and an inclination of only 1.39. A search of older records showed that 133P had been observed previously in 1979 as an inactive asteroid. So it is another object that was catalogued as both a comet and an asteroid.

The explanation for 133P was that, given its position in the asteroid belt, where maximum solar surface temperatures are only about 48 C (54 F), it likely acquired some water in the form of ice from the solar nebula. Like in comets, the ices near the surface of 133P sublimated early in its history, leaving an insulating layer of nonvolatile material covering the ice at depth. Then a random impact from a piece of asteroidal debris punched through the insulating layer and exposed the buried ice. Comet 133P has shown regular activity at the same location in its orbit for at least three orbits since it was discovered.

Twelve additional objects in asteroidal orbits have been discovered since that time, most of them also in the outer main belt. They are sometimes referred to as main belt comets, though the more recently accepted term is active asteroids.

The latter half of the 20th century saw a massive leap forward in the understanding of the solar system as a result of spacecraft visits to the planets and their satellites. Those spacecraft collected a wealth of scientific data close up and in situ. The anticipated return of Halleys Comet in 1986 provided substantial motivation to begin using spacecraft to study comets.

The first comet mission (of a sort) was the International Cometary Explorer (ICE) spacecrafts encounter with Comet 21P/Giacobini-Zinner on September 11, 1985. The mission had originally been launched as part of a joint project by the U.S. National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) known as the International Sun-Earth Explorer (ISEE). The mission consisted of three spacecraft, two of them, ISEE-1 and -2, in Earth orbit and the third, ISEE-3, positioned in a heliocentric orbit between Earth and the Sun, studying the solar wind in Earths vicinity.

In 1982 and 1983 engineers maneuvered ISEE-3 to accomplish several gravity-assist encounters with the Moon, which put it on a trajectory to encounter 21P/Giacobini-Zinner. The spacecraft was targeted to pass through the ion tail of the comet, about 7,800 km (4,800 miles) behind the nucleus at a relative velocity of 21 km (13 miles) per second, and returned the first in situ measurements of the magnetic field, plasma, and energetic particle environment inside a comets tail. Those measurements confirmed the model of the comets ion tail first put forward in 1957 by the Swedish physicist (and later Nobel Prize winner) Hannes Alfvn. It also showed that H2O+ was the most common ion in the plasma tail, consistent with the Whipple model of an icy conglomerate nucleus. However, ICE carried no instruments to study the nucleus or coma of the comet.

In 1986 five spacecraft were sent to encounter Halleys Comet. They were informally known as the Halley Armada and consisted of two Japanese spacecraft, Suisei and Sakigake (Japanese for comet and pioneer, respectively); two Soviet spacecraft, Vega 1 and 2 (a contraction of Venus-Halley using Cyrillic spelling); and an ESA spacecraft, Giotto (named after the Italian painter who depicted the Star of Bethlehem as a comet in a fresco painted in 130506).

Suisei flew by Halley on March 8, 1986, at a distance of 151,000 km (94,000 miles) on the sunward side and produced ultraviolet images of the comets hydrogen corona, an extension of the visible coma seen only in ultraviolet light. It also measured the energetic particle environment in the solar wind ahead of the comet. Sakigakes closest approach to the comet was on March 11, 1986, at a distance of 6.99 million km (4.34 million miles), and it made additional measurements of the solar wind.

Before flying past Halleys Comet, the two Soviet spacecraft had flown by Venus and had each dropped off landers and balloons to study that planet. Vega 1 flew through the Halley coma on March 6, 1986, to within 8,889 km (5,523 miles) of the nucleus and made numerous measurements of the coma gas and dust composition, plasma and energetic particles, and magnetic field environment. It also returned the first picture ever of a solid cometary nucleus. Unfortunately, the camera was slightly out of focus and had other technical problems that required considerable image processing to see the nucleus. Vega 2 fared much better when it flew through the Halley coma on March 9 to within 8,030 km (4,990 miles) of the nucleus, and its images clearly showed a peanut-shaped nucleus about 16 by 8 km (10 by 5 miles) in diameter. The nucleus was also very dark, reflecting only about 4 percent of the incident sunlight, which had already been established from Earth-based observations.

Both Vega spacecraft carried infrared spectrometers designed to measure the temperature of the Halley nucleus. They found quite warm temperatures between 320 and 400 K (47 and 127 C [116 and 260 F]). That surprised many scientists who had predicted that the effect of water ice sublimation would be to cool the nucleuss surface; water ice requires a great deal of heat to sublimate. The high temperatures suggested that much of the nucleuss surface was not sublimating, but why?

Whipples classic paper in 1950 had suggested that as comets lost material from the surface, some particles were too heavy to escape the weak gravity of the nucleus and fell back onto the surface, forming a lag deposit. That idea was later studied by American astronomer and author David Brin in his thesis work with his adviser, Sri Lankan physicist Asoka Mendis, in 1979. As the lag deposit built up, it would effectively insulate the icy materials below it from sunlight. Calculations showed that a layer only 10100 cm (439 inches) in thickness could completely turn off sublimation from the surface. Brin and Mendis predicted that Halley would be so active that it would blow away any lag deposit, but that was not the case. Only about 30 percent of Halleys sunlit hemisphere was active. Bright dust jets could be seen coming from specific areas on the nucleus surface, but much of the surface showed no visible activity.

Giotto flew through Halleys coma on March 14, 1986, and passed only 596 km (370 miles) from the nucleus. It returned the highest-resolution images of the nucleus and showed a very rugged terrain with mountain peaks jutting up hundreds of metres from the surface. It also showed the same peanut shape that Vega 2 saw but from a different viewing angle and with much greater visible detail. Discrete dust jets were coming off the nucleus surface, but the resolution was not good enough to reveal the source of the jets.

Giotto and both Vega spacecraft obtained numerous measurements of the dust and gas in the coma. Dust particles came in two types: silicate and organic. The silicate grains were typical of rocks found on Earth such as forsterite (Mg2SiO4), a high-temperature mineralthat is, one which would be among the first to condense out of the hot solar nebula. Analyses of other grains showed that the comet was far richer in magnesium relative to iron. The organic grains were composed solely of the elements carbon, hydrogen, oxygen, and nitrogen and were called CHON grains based on the chemical symbol for each of those elements. Larger grains were also detected that were combinations of silicate and CHON grains, supporting the view that comet nuclei had accreted from the slow aggregation of tiny particles in the solar nebula.

The three spacecraft also measured gases in the coma, water being the dominant molecule but also carbon monoxide accounting for about 7 percent of the gas relative to water. Formaldehyde, carbon dioxide, and hydrogen cyanide were also detected at a few percent relative to water.

The Halley Armada was a rousing success and resulted from international cooperation by many nations. Its success is even more impressive when one considers that the spacecraft all flew by the Halley nucleus at velocities ranging from 68 to 79 km per second (152,000 to 177,000 miles per hour). (The velocities were so high because Halleys retrograde orbit had it going around the Sun in the opposite direction from the spacecraft.)

Giotto was later retargeted using assists from Earths gravity to pass within about 200 km (120 miles) of the nucleus of the comet 26P/Grigg-Skjellrup. The flyby was successful, but some of the scientific instruments, including the camera, were no longer working after being sandblasted at Halley.

The next comet mission was not until 1998, when NASA launched Deep Space 1, a spacecraft designed to test a variety of new technologies. After flying past the asteroid 9969 Braille in 1999, Deep Space 1 was retargeted to fly past the comet 19P/Borrelly on September 22, 2001. Images of the Borrelly nucleus showed it to be shaped like a bowling pin, with very rugged terrain on parts of its surface and mesa-like formations over a large area of it. Individual dust and gas jets were seen emanating from the surface, but the activity was far less than that of Halleys Comet.

The NASA Stardust mission was launched in 1999 with the goal of collecting samples of dust from the coma of Comet 81P/Wild 2. At a flyby speed of 6.1 km per second (13,600 miles per hour), the dust samples would be completely destroyed by impact with a hard collector. Therefore, Stardust used a material made of silica (sand) called aerogel that had a very low density, approaching that of air. The idea was that the aerogel would slow the dust particles without destroying them, much as a detective might shoot a bullet into a box full of cotton in order to collect the undamaged bullet. It worked, and thousands of fine dust particles were returned to Earth in 2006. Perhaps the biggest surprise was that the sample contained high-temperature materials that must have formed much closer to the Sun than where the comets formed in the outer solar system. That unexpected result meant that material in the solar nebula had been mixed, at least from the inside outward, during the formation of the planets.

Stardusts images of the nucleus of Wild 2 showed a surface that was radically different from either Halley or Borrelly. The surface appeared to be covered with large flat-floored depressions. Those were likely not impact craters, as they did not have the correct morphology and there were far too many large ones. There was some suggestion that it was a very new cometary surface on a nucleus that had not been close to the Sun before. Support for that was the fact that Wild 2 had been placed into its current orbit by a close Jupiter approach in 1974, reducing the perihelion distance to about 1.5 AU (224 million km, or 139 million miles). Before the Jupiter encounter, its perihelion was 4.9 AU (733 million km, or 455 million miles), beyond the region where water ice sublimation is significant.

In 2002 NASA launched a mission called Contour (Comet Nucleus Tour) that was to fly by Enckes Comet and 73P/Schwassman-Wachmann 3 and possibly continue on to 6P/DArrest. Unfortunately, the spacecraft structure failed when leaving Earth orbit.

In 2005 NASA launched yet another comet mission, called Deep Impact. It consisted of two spacecraft, a mother spacecraft that would fly by Comet 9P/Tempel 1 and a daughter spacecraft that would be deliberately crashed into the comet nucleus. The mother spacecraft would take images of the impact. The daughter spacecraft contained its own camera system to image the nucleus surface up to the moment of impact. To maximize the effect of the impact, the daughter spacecraft contained 360 kg (794 pounds) of solid copper. The predicted impact energy was equivalent to 4.8 tonnes of TNT.

The two spacecraft encountered Tempel 1 on July 4, 2005. The impactor produced the highest-resolution pictures of a nucleus surface ever, imaging details less than 10 metres (33 feet) in size. The mother spacecraft watched the explosion and saw a huge cloud of dust and gas emitted from the nucleus. One of the mission goals was to image the crater made by the explosion, but the dust cloud was so thick that the nucleus surface could not be seen through it. Because the mission was a flyby, the mother spacecraft could not wait around for the dust to clear.

Images of the Tempel 1 nucleus were very different from what had been seen before. The surface appeared to be old, with examples of geologic processes having occurred. There was evidence of dust flows across the nucleus surface and what appeared to be two modest-sized impact craters. There was evidence of material having been eroded away. For the first time, icy patches were discovered in some small areas of the nucleus surface.

For the first time, a mission was also able to measure the mass and density of a cometary nucleus. Typically, the nuclei are too small and their gravity too weak to affect the trajectory of the flyby spacecraft. The same was true for Tempel 1, but observations of the expanding dust cloud from the impact could be modeled so as to solve for the nucleus gravity. When combined with the volume of the nucleus as obtained from the camera images, it was shown that the Tempel 1 nucleus had a bulk density between 0.2 and 1.0 gram per cubic centimetre with a preferred value of 0.4 gram per cubic centimetre, less than half that of water ice. The measurement clearly confirmed ideas from telescopic research that comets were not very dense.

After the great success of Stardust and Deep Impact, NASA had additional plans for the spacecraft. Stardust was retargeted to go to Tempel 1 and image the crater from the Deep Impact explosion as well as more of the nucleus surface not seen on the first flyby. Deep Impact was retargeted to fly past 103P/Hartley 2, a small but very active comet.

Deep Impact, in its postimpact EPOXI mission, flew past Comet Hartley 2 on November 4, 2010. It imaged a small nucleus about 2.3 km (1.4 miles) in length and 0.9 km (0.6 mile) wide. As with Halley and Borrelly, the nucleus appeared to be two bodies stuck together, each having rough terrain but covered with very fine, smooth material at the neck where they came together. The most amazing result was that the smaller of the two bodies making up the nucleus was far more active than the larger one. The activity on the smaller body appeared to be driven by CO2 sublimationan unexpected result, given that short-period comets are expected to lose their near-surface CO2 early during their many passages close to the Sun. The other half of the nucleus was far less active and only showed evidence of water ice sublimation. The active half of the comet also appeared to be flinging baseball- to basketball-sized chunks of water ice into the coma, further enhancing the gas production from the comet as they sublimated away.

The EPOXI images also showed that the nucleus was not rotating smoothly but was in complex rotationa state where the comet nucleus rotates but the direction of the rotation pole precesses rapidly, drawing a large circle on the sky. Hartley 2 was the first encountered comet to exhibit complex rotation. It was likely driven by the very high activity from the smaller half of the nucleus, putting large torques on the nucleus rotation.

Stardust/NExT (New Exploration of Tempel 1) flew past Tempel 1 on February 14, 2011, and it imaged the spot where the Deep Impact daughter spacecraft had struck the nucleus. Some scientists believed that they saw evidence of a crater about 150 metres (500 feet) in diameter, but other scientists looked at the same images and saw no clear evidence of a crater. Some of the ambiguity was due to the fact that the Stardust camera was not as sharp as the Deep Impact cameras, and some of it was also due to the fact that sunlight was illuminating the nucleus from a different direction. The debate over whether there was a recognizable crater lingers on.

Among the new areas observed by Stardust-NeXT there was further evidence of geologic processes, including layered terrains. Using stereographic imaging, the scientists traced dust jets observed in the coma back to the nucleus surface, and they appeared to originate from some of the layered terrain. Again, the resolution of the images was not good enough to understand why the jets were coming from that area.

In 2004 ESA launched Rosetta (named after the Rosetta Stone, which had unlocked the secret of Egyptian hieroglyphics) on a trajectory to Comet 67P/Churyumov-Gerasimenko (67P). Rendezvous with 67P took place on August 6, 2014. Along the way, Rosetta successfully flew by the asteroids 2849 Steins and 21 Lutetia and obtained considerable scientific data. Rosetta uses 11 scientific instruments to study the nucleus, coma, and solar wind interaction. Unlike previous comet missions, Rosetta will orbit the nucleus until December 2015, providing a complete view of the comet as activity begins, reaches a maximum at perihelion, and then wanes. Rosetta carried a spacecraft called Philae that landed on the nucleus surface on November 12, 2014. Philae drilled into the nucleus surface to collect samples of the nucleus and analyze them in situ. As the first mission to orbit and land on a cometary nucleus, Rosetta is expected to answer many questions about the sources of cometary activity.

The rest is here:

Comet | astronomy | Britannica.com

Comet Goldfish, Sarasa Comet Goldfish Information, Care …

Black Moor GoldfishBubble Eye GoldfishCelestial Eye GoldfishComet GoldfishCommon GoldfishFantail GoldfishLionhead GoldfishOranda GoldfishPearlscale GoldfishRanchu GoldfishRedcap Oranda GoldfishRyukin GoldfishShubunkin GoldfishTelescope GoldfishVeiltail GoldfishComet Goldfish look just like regular goldfish but with a much longer andmore deeplyforked tail fin!

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The Comet Goldfish is also called the Comet-tail Goldfish or Pond Comet. This fish was the first variety of single-tail goldfish to be developed with a long caudal (tail) fin. It was developed in the United States from the Common Goldfish in the early 19th century, presumably by Hugo Mullert of Philadelphia, who then introduced them in quantity into the market.

Being a further development of the Common Goldfish, the Comet is sometimes confused for its close relative. The Comet Goldfish and Common Goldfishhave an almost identical body shape. However, the fins on the Comet Goldfish are much longer, especially the caudal (tail) fin. Its caudal fin is also more deeply forked. On both these fish,the caudal fin is held fully erect.

The adult size of the Comet Goldfish is also smaller than the Common Goldfish. Yet they are every bit as durable and can be kept in either an aquarium or outdoor pond. Both fish are inexpensive and readily available.

The Comet is generally more reddish orange in color while the Common Goldfish is more orange. While the Comet Goldfish is typically areddish orange, this fish isalso available in yellow, orange, white, and red. They can also be found as a bi-color red/white combination, and occasionally they are available with nacreous (pearly) scales, giving them a variegated color.

Other types of Comet include the Sarasa Comet. This variety has long flowing fins and is characterized by a red-and-white coloration that holds a resemblance to a koi color pattern called 'Kohaku.'Additionally, the Tancho Single-tail Comet is a silvervariety with a red patch on its head.

One of the hardiest of the goldfish varieties, Comet Goldfish are recommended for beginners. They are an easy fish to keep as they are not picky and will readily eat what is offered.

These fish can be quite personable and are delightful to watch. They are some of the most graceful of the elongated goldfish, and this quality isemphasized by their long tails. They are active, rapid swimmers and tend to leap out of the water occasionally, so having a lid on an aquarium is good idea. They are also very social and thrive well in a community.

Along with the other elongated goldfish, such as the Common Goldfish and the Shubunkin Goldfish, the Comet varieties make good pond fish. They are hardy and can tolerate cold water temperatures. They are moderate in size but are active and fast, so will get along well with Koi. Also, Comets usually won't uproot plants, but they will readily spawn. Care should be taken, so they don't quickly overpopulate your pond.

Comet Goldfish - Quick Aquarium Care

Habitat: Distribution / Background

The goldfish of today are descendants of a species of wild carp known as the Prussian Carp, Silver Prussian carp, or Gibel Carp Carassius gibelio (syn: Carassius auratus gibelio), which was described by Bloch in 1782. These wild carp originated in Asia; Central Asia (Siberia). They inhabit the slow moving and stagnant waters of rivers, lakes, ponds, and ditches feeding on plants, detritus, small crustaceans, and insects.

For many years, it was believed that goldfish had originated from the Crucian Carp Carassius carassius described by Linnaeus in 1758. This fish has a wide range across the waters of the European continent, running west to east from England to Russia, north to Scandinavian countries in the Arctic Circle and as far south as the central France and the Black Sea. However, recent genetic research points to C. gibelio as a more likely ancestor.

Goldfish were originally developed in China. The first goldfish werenormally a silver or gray color, but early in the Jin Dynasty, somewhere between the years 265 - 420, breeders noted a natural genetic mutation thatproduceda yellowish orange color. It became common practice to breed this pretty golden fish for ornamental garden ponds.

By the 1500's goldfish were traded to Japan, to Europe in the 1600's, and to America by the 1800's. The majority of the fancy goldfish were being developed by Asianbreeders. The results of this centuries-long endeavor is the wonderful goldfish colors and forms we see today. Domesticated goldfish are now distributed world-wide.

The Comet Goldfish was the first variety of the single-tail goldfish to be developed with a long caudal (tail) fin. It was developed in the United States from the Common Goldfish in the early 19th century, presumably by Hugo Mullert of Philadelphia, who then introduced them in quantity into the market. The Comet Goldfishis one of more than 125 captive-bred varieties of goldfish that have been developed.

Description

The Comet Goldfish is an elongated, flat-bodied variety of goldfish. The head is wide but short, and its body tapers smoothlyfrom its back and belly to the base of its caudal fin (tail fin). The caudal fin is long anddeeply forked and generally stands fully erect. Comets have a natural life span of up to 14 years, though possibly longer if kept in optimal conditions.

The Comet Goldfish is a bit smaller than the Common Goldfish, but even so, the environment it is kept in will mostly determinewhether your pet grows to its full potential size. In an average 15 gallon tank, if well cared for and not crowded, they can grow up to about 4 inches (10 cm), while in a larger, uncrowded tank, they can grow larger, generally reaching about 7 or 8 inches (17.78 - 20.32 cm). If kept in a spacious pond, they can reach over 12 inches (30+ cm).

They are primarily a reddish orange color, but they are also available in yellow, orange, white, and red. Some Comet Goldfish come in abi-color red/white combination, and occasionally they are available with nacreous (pearly) scales, giving them a variegated color.

Comet Goldfish can and do naturally change color, but color changes are believed to be influenced by diet and the amount of light. Aquarists often report the reds and oranges of their goldfish changing to white. A fresh dietalong with good lighting and available shadeare suggested as the best ways to maintain the original coloration. Even so, these measuresare not always successful.

Other types of Comet Goldfish include the Sarasa Comet. This variety has long flowing fins and is characterized by a red-and-white coloration that holds a resemblance to a koi color pattern called 'Kohaku.'The Tancho Single-tail Comet is a silver variety with a red patch on its head.

Fish Keeping Difficulty

Comet Goldfish are some of the hardier species of goldfish. They are very undemanding of water quality and temperature. They can do well in a goldfish aquariumor even a pond as long as the environment is safe and their tankmates are not competitive.

Many people will keep goldfish in an aquarium with no heater or filtration, but for the best success, provide them the same filtration, especially biological filtration, that other aquarium residents enjoy.

Foods and Feeding

Since they are omnivorous, the Comet Goldfish will generally eat all kinds of fresh, frozen, and flake foods. To keep a good balance, give them a high quality flake food every day. To care for your goldfish, feed brine shrimp (either live or frozen), blood worms, Daphnia, or tubifex worms as a treat. It is usually better to feed freeze-dried foods as opposed to live foods to avoid parasites and bacterial infections that could be present in live foods.

Aquarium Care

These goldfish are hardy and easy to keep in a well maintained tank. Minimum tank size is 15 gallons, so make sure water changes are frequent in such as small tank. Regular weekly water changes of 1/4 to 1/3 is strongly recommended to keep these fish healthy. Snails can be added as they reduce the algae in the tank, helping to keep it clean.

Aquarium Setup

Setting up a goldfish aquarium in a manner that will keep your fish happy and healthy is the first step to success. The shape and size of the aquarium is important and depends upon the number of goldfish you are going to keep. These fish need a lot of oxygen and produce a lot of waste. Good filtration, especially biological filtration, is very helpful in maintaining the water quality of the aquarium. A filtration system will remove much of the detritus, excess foods, and waste, which keeps the tank clean and maintains the general health of the goldfish.

Goldfish are a cold water fish and will do best at temperatures between 65 - 72 F (18- 22 C). The Comet Goldfish are one of the most hardy varieties and can tolerate temperatures a few degrees above freezing, as long as the cooling drops only a few degrees a day. A quick temperature drop can kill them, so if you live in a very cold climate,a heater is advisable.

Provide a gravel substrate to help create a natural and comfortable environment for your fish. You can add some decor, but make sure that all ornamentation is smooth with no protruding points or sharp edges. Smooth rocks or driftwood should be used sparingly if at all. Aquarium plants would be the best choice of aquarium decor for goldfish, but unfortunately these fish are diggers. Consequently live plants may be uprooted. Artificial plants make a good substitute and silk plants are safer than plastic ones.

Most aquariums come with a cover that includes lighting. A cover for the tank is desirable as it reduces evaporation and though they are not prone to jumping, on occasion some gold fish will jump out. Lighting is not essential for goldfish, but does make the aquarium a nice showpiece and lighting will help if you have live plants.

Social Behaviors

Goldfish are very social animals and thrive in a community. Not only are they a great community fish, but they are great scavengers as well. It is really not necessary to add other scavengers or other bottom feeders to the aquarium when you have goldfish.

Most fancy goldfish will thrive in both freshwater and tropical aquariums as long as there are no aggressive or territorial fish in the tank. Some good tankmates for fancy goldfish are the Chinese Blue Bitterling and the Northern Redbelly Dace. Comet Goldfish can be kept with other varieties of elongated goldfish, such as the Common Goldfish and the Shubunkin, and they also do fine with Koi.

Sex: Sexual differences

During the breeding season, the male has white prickles, called breeding tubercles, on its gill covers and head. Seen from above, a female will have a fatter appearance when she is carrying eggs. It is impossible to sex Goldfish when they are young and not in breeding season, but generally the male is smaller and more slender than the female.

Breeding / Reproduction

Comet Goldfish are egg layers that spawn readily in the right conditions. They can be bred in groups as small as five individuals, but they are very social animals and likely to breed in larger groups as well. The only time Goldfish will spawn in the wild is when spring arrives. To spawn them in the aquarium, you will need to mimic the conditions found in nature.

Provide an aquarium that is at least 20 gallons and make sure the fish are healthy and disease free. Some breeders suggest you treat them for parasites. Many breeders will also separate the males and females for a few weeks prior to breeding to help increase their interest in spawning. Introduce the fish into the breeding tank at the same time. The tank will need a lush environment with solid surfaces for the spawning process and for the eggs to adhere to. Bushy, oxygenating plants, such as Anacharis, work well for this, though artificial plants or fibrous spawning mops can also be used.

To induce spawning, the temperature can be slowly dropped to around 60 F (11 C) and then slowly warmed at a rate of 3 F (2 C) per day until they spawn. Spawning generally begins when the temperatures are between 68 and 74 F (20-23 C). Feeding lots of high protein food such live brine shrimp and worms during this time will also induce spawning. Feed small amounts three times a day, but don't overfeed. Uneaten scraps will sink to the bottom and foul the water. Maintain the breeding tank with partial water changes of up to about 20% per day.

Before spawning, as the temperature increases, the male will chase the female around the aquarium in a non-aggressive way. This can go on for several days, and the fish will intensify in color. During the spawn, the fish will gyrate from side to side, and the male will push the female against the plants. This stimulates the female to drop tiny eggs which the male will then fertilize. The eggs will adhere by sticky threads to the plants or spawn mop. Spawning can last two or three hours and can produce up to 10,000 eggs.

At this point, the parents will start to eat as many eggs as they can find. For this reason, it is best to remove the parents after spawning is complete. The fertilized eggs will hatch in 4 to 7 days, depending on the temperature. You can feed the newly hatched goldfish specialty fry foods until they become big enough to eat flake or brine shrimp, or you can offer the same food as you feed the parents as long as it is crushed very small. At first, the fry are a dark brown or black color in order to better hide and not be eaten by larger fish. They gain their adult color after several months and can be put in with larger fish once they reach about 1 inch long. See Breeding Freshwater Fish - Goldfish for more information on breeding Goldfish.

Fish Diseases

In properly maintained goldfish aquariums or ponds, goldfish illness is largely preventable. Even so, goldfish illnesses can occur, and if left untreated, may prove fatal. Goldfish are hardy, though, and if treated in a timely manner, most will make a full recovery.

When treating individuals, it is usually best to move the afflicted fish into a separate tank with no gravel or plants and do regular partial water changes. However, if the disease is apparent throughout the main tank, it may be best to do the treatments there. Whether treating in a hospital tank or your main tank, read and follow the manufacturer's instructions for any medication. Some medications can adversely affect the water quality by destroying beneficial bacteria. You may also need to remove the carbon from the filtration system, as carbon will absorb many medications, making the treatment ineffective.

Goldfish diseases are mostly the same as those that afflict other freshwater fish, and the symptoms and treatment of goldfish are also similar. The main types of fish diseases include bacterial infections, fungal infections, parasites, and protozoa. There are also other ailments caused by injury, poor nutrition, or bad water conditions.

One of the more common problems is Ich, which is a protozoan disease. Ich is easy to identify because your fish looks like it is sprinkled with salt. Though Ich is easily treated, like other protozoan diseases, it can be fatal if not caught quickly. Some other protozoan diseases are Costia, which causes a cloudiness of the skin, and Chilodonella, which will cause a blue-white cloudiness on the skin.

External parasites are fairly common, too, but pretty easy to treat and usually not fatal when treated. These include flukes, which are flatworms about 1 mm long with hooks around their mouths. They infest the gills or body of the fish. Another type of parasite is fish lice (Argulus), flattened, mite-like crustaceans about 5 mm long that attach themselves to the body of the goldfish. Lastly, anchor worms look like threads coming out of the fish.

Some bacterial infections include Dropsy, an infection in the kidneys that can be fatal if not treated quickly. Fish Tuberculosis is indicated by the fish becoming emaciated (having a hollow belly). For this illness, there is no absolute treatment, and it can be fatal. Tail/Fin Rot may also be bacterial, though the reduced tail or fins can be caused by a number of factors as well. There is also fungus, a fungal infection, and Black Spot or Black Ich, which is a parasitic infection.

Swim Bladder Disease is an ailment indicated by fish swimming in abnormal patterns and having difficulty maintaining their balance. This can be caused by a number of things: constipation, poor nutrition, a physical deformity, or a parasitic infection. Feeding frozen peas (defrosted) has been noted to help alleviate the symptoms and correct the problem in some cases.

Other miscellaneous ailments include Cloudy Eye, which can be caused by a variety of things ranging from poor nutrition, bad water quality, and rough handling. It can also be the result of other illnesses, such as bacterial infections. Constipation is indicated by a loss of appetite and swelling of the body, and the cause is almost always diet. Then there are wounds and ulcers. Wounds can become infected, creating ulcers. Wounds can develop either bacterial or fungal infections, or both, and must be treated. There are treatments for each of these diseases individually and treatments that handle both. For more in-depth information about goldfish diseases and illnesses, see Goldfish Care; Fancy Goldfish and Goldfish Diseases.

Availability

The Comet Goldfish is inexpensive andreadily available in fish stores and online.

References

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Comet Goldfish, Sarasa Comet Goldfish Information, Care ...

Comets look to attack defensively – Kokomo Perspective

After completing 10 years as the head coach, Josh Edwards and his Comets put together their best season since 2011, with a 4-6 record last year. Now, Edwards plans to build on the teams success with his upperclassmen.

Though the Comets on paper did not look extremely impressive last year, part of that was due to only playing three quarters of the game. Of the six losses, two of them were lost in the fourth quarter, one at Oak Hill and one at Madison-Grant. Though the team has fallen short on some outcomes, its biggest blowout was by 40 points. With the capacity to outscore a team in that fashion, Edwards is counting on utilizing his strong-skilled veteran players to go above a .500 season.

Taking the snaps for Eastern will be quarterback Garrett Hetzner. Hetzner has put time in the weight room over the off-season to build his body frame. At 6-feet 3-inches and 180-pounds, he has the size and strength to pass or carry the ball where it needs to go.

This will be an exciting season for him. Hes been working hard in gym, asking a lot of good questions. Most importantly, hes trying to better his teammates, said Edwards.

At Hetzners disposal will be three returning senior wide receivers, Clayton McKillip, Braden Sparks, and Tyler TP Gilbert. With each receiver comes a unique skillset.

McKillip has the speed necessary to beat almost any cornerback off of the line. Sparks has the agility and mental know-how to beat off defenders. TP will be that guy who will make it happen. Between the three of them, itll be fun to watch, said Edwards.

On the other side of the ball, Edwards and his squad of nine returning starters do not have too much to stress over.

Last year we created a hybrid defense that would fit our kids the best, knowing we would have most of the kids back this year. Weve pretty much kept the scheme the same for the most part, minus a few adjustments, said Edwards. Overall, I think well have a lot of continuity that should carryover from last year to this year.

After implementing its hybrid defense, the Comets were able to shave 10 points allowed per game off of its average. With the majority of its defense returning, mixed in with several key players on offense, Edwards hopes to knockout Oak Hill in the season opener come Aug. 18.

Oak Hill has literally been circled on our schedule since last year after what happened. When we let them score 20 points in the fourth quarter to beat us, its all Ive been focused on since last year, said Edwards.

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Comets look to attack defensively - Kokomo Perspective

Blue Devils beat Comets – hngnews.com

Lodi (1-0, 0-0) posted a convincing 34-6 non-conference win over Delavan-Darien/Williams Bay (0-1, 0-0) Aug. 18 at Lodi. The Blue Devils first quarter scoring opportunities were stopped short by turnovers, but the Capitol North team exploded for three second quarter points to take a 21-0 lead into the halftime intermission.

The Lodi defense kept the Comet offense off the field and in check throughout the first two quarters.

Week one is always interesting because you are never quite sure how quickly the players will get things going in the first full competition of the year. We were extremely pleased with the way the offense moved the ball down the field on the opening drive. The effort that was put forth from the very beginning of the game was impressive. The team played well but only showed a small glimpse of what they are capable, said Lodi Head Coach David Puls. The team will have to make many improvements throughout the season if they want to reach their goals. We need to have a good week of practice and correct a lot of blocking in the run game and the execution and decision making in the pass game, on defense we need to work on tackling, coverage, shedding blocks, staying low, and controlling our gaps. We have a great group of seniors and we expect them to keep things going in the right direction.

Lodis first score came early in the second quarter as senior Jacob Heyroth ran the ball in from 3 yards out (Savannah Curtis kick) to give the Blue Devils a 7-0 advantage.

A short time later, Heyroth sprinted 62 yards on a punt return (Curtis kick) to raise the Lodi advantage to 14-0.

Cameron McDonald connected with Kade Crissinger on an eight yard scoring toss (Curtis kick) later in the quarter to give the Blue devils a commanding 21-0 lead entering the third quarter.

McDonald teamed up with Dominic Scola on a 35-yard catch and run (Curtis kick) in the third quarter for a 28-0 Lodi lead.

Ben Rashid scored the Blue Devils final touchdown on a one yard run (Curtis kick unsuccessful) to raise the Lodi advantage to 34-0.

Delavan-Darien/Williams Bay finally lit up their side of the score board with an 18-yard touchdown run by Dakota Williams (Jaime Flores extra point unsuccessful) to close the final score to 34-6.

The Blue Devil offense posted 203 yards rushing and added another 77 yards through the air.

Heyroth gained 124 yards rushing in 22 carries and sophomore Colton Nicolay chipped in 45 yards rushing on 11 carries to pace the Blue Devil rushing game.

Both backs ran hard and made some big plays. Cameron McDonald had a couple of pass miscalculations early on, but then responded admirably with a couple of completions on screen passes and a couple touchdowns, Puls said.

McDonald completed five of seven passes for 77 yards and two touchdown passes. He was picked off twice by the Comet defense. Scola (35 yards), Hyroth (18 yards), Nicolay (12 yards), Crissinger (eight yards) and Rashid (four yards) each caught a pas during the game.

Lodi held the Comets to just 34 yards rushing in 26 carries and 118 yards passing.

Owen Jelinek led the team with five tackles and Max Barreau recorded four tackles (two TFLs, one sack, one forced fumble). Will Richards recorded 2 TFLs with a fumble recovery. Austin Soehle also had a fumble recovery, multiple quarterback pressures, and a pass defended. Twenty different Lodi players recorded at least one tackle in the game.

Overall, it was a great night for Parents Night and any win is a good win, Puls said. We learned a lot about our team Friday and now we need to move forward. We play the at Wisconsin Dells High School [Aug. 24] at 7 p.m. The Dells got a win against Thorp this past Friday and they are a much improved team. They are riding high after their win and will be looking to keep things rolling when they play us on Thursday. We expect our team to be ready and compete at the highest level,

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Blue Devils beat Comets - hngnews.com

Comets, Redskins travel to Reading – The Hillsdale Daily News

Matthew Lounsberry mlounsberry@hillsdale.net mlounsberryHDN

READING Jonesville and Camden-Frontier traveled to Reading on Tuesday night for a three-team match between local Hillsdale County schools.

The Comets came out the big winners, going 2-0.

Today, I was really impressed with the energy level and the [communication] amongst the players in the match and before [each] serve, said Jonesville coach Sydney Barrett. Thats something we talked a lot about at practice yesterday.

Jonesville opened the night against Camden-Frontier, and had their hands full with the Redskins.

Camden-Frontier opened the match with a 6-4 lead before a 9-4 run gave the Comets a 13-10 advantage. Following a Redskin timeout, Camden-Frontier battled back to force ties at 16, 19, 20 and 21 before Jonesville scored the final four points to take Game 1.

Camden gets so many balls up in their defense. They hustle, they dont let anything hit the floor, theyre smart and they know where to place the ball, Barrett said.

Game 2 provided another back-and-forth affair. The Comets grabbed an early 6-4 lead, but the teams played to ties at 7, 10, 14, and 15.

Jonesville rallied to take a 20-17 lead and never gave it up, winning 25-20 to take the match.

I told them, Defense is going to win the match. Camden was going to take points from us, they earned a lot of points as well. We needed to be ready on defense, Barrett said.

Camden-Frontier showed that they could play with the older Comet squad, but couldnt put together enough runs to finish Jonesville off.

One thing weve been working on is our consistency. In our Jonesville game, we just had way more mistakes than they had, said Redskins coach Dawn Follis.

Jonesville was hitting in, and making us make the play. They werent all kills, but we were making our own mistakes.

After dispatching Camden-Frontier, the Comets turned their attention to Reading, grabbing an early 8-1 lead in Game 1. Jonesville extended their lead to 17-5, forcing the Rangers into a timeout.

When we went up against Jonesville, we looked like deer in headlights, said Reading coach Nicole Bailey.

The Rangers were unable to grab any momentum, and Jonesville took the opening game by a 25-9 final score.

In the encore, Reading seemed to settle in a bit, grabbing a 10-7 lead. However, the Comets scored five straight points to take a 12-10 lead, and would never give up the advantage, cruising to a 25-13 win.

Barrett credited her seven seniors with helping her team get off to a strong start so far this season.

The group of seniors are all really exceptional leaders. I could have them all be captains. I cant have seven captains, but I could. Thats a good problem to have, she said.

They give a ton of feedback, so if theres a new face on the floor, theyre so good about explaining things. Theyre just really great leaders, they want to win and theyre sharing that love with the underclassmen, so thats really exciting.

Middle hitter Samantha Dunn led Jonesville with 11 kills, converting over 75 percent of her attempts. Outside hitter Hanna Purdy added 10 kills and 18 digs.

Koryn Playford had a solid performance on the outside with eight kills and 11 digs. Libero Lauren Mains led the team in digs with 21, while setter Teya Nichols had a strong night with 20 assists.

We passed pretty well, so we could run our middle a lot. Sam and Amber [Gordon] both got a lot of attempts in the middle and a lot of kills. That opens up the outside, and that played a huge role tonight, Barrett said.

When we pass well, were going to be able to spread the offense out. Teya did a nice job of that tonight.

Camden-Frontier and Reading squared off in the final match of the day, with the Redskins sweeping the Rangers 2-0.

In the opener, the teams were deadlocked early, with ties at 7-7, 10-10 and 13-13. Camden-Frontier then seized momentum, finishing Game 1 with a 12-6 run for a 25-19 win.

I spent a lot of time in timeouts saying, Yes, youve made mistakes, but how are you going to overcome them? We all make mistakes, we have to find a way to overcome them, Bailey said.

Against Camden, I thought we played with a little more confidence.

The Redskins got off to a quicker start in Game 2, seizing a 6-1 advantage early. Reading was unable to recover, as the lead grew to 11-6, 15-9 and 21-13 before Camden-Frontier put the Rangers away, 25-15.

Were still working on maturity in a lot of our positions. I know the end of the season will be very different than the beginning of the season, Follis said. They have the talent, its just that consistency to to it repetitively.

Camden-Frontier was led by sophomore Jordan Stump, who finished with 15 assists and 15 kills. Fellow sophomores Frances Churchwell (25 digs) and Alicia Fackler (18 assists) also made big contributions.

Even though they are sophomores, they do bring a lot of experience, Follis said. A lot of my team plays club all the time. Yes, theyre young, but I expect a lot out of them because theyve played together for so long.

The Redskins also got a boost from Hillsdale Academy transfer Brooklyn Gravel, who finished with 13 kills and six aces.

Shes got height, shes got hitting and she can pass. So, shes got the skills all the way around, Follis said. Shes had a ball in her hand for [most] of her life. When you have a 510 person walk in whos had a ball in her hand their whole life, you let them in.

She has played with a core of my team [in club volleyball] almost more than some of my regular players have played with them. With her walking on to my court, theres four of them who have played together a lot.

Rounding out the statistical impact for Camden-Frontier was Maddie Vondron with 9 kills, Marin Page with five kills and Layne Cooney with five kills.

In past years, we usually just had a couple [hitters], Follis said, noting that the Redskins were able to spread the offense around. This year I have five hitters that we can go to. Weve got more height than weve had in the past.

All three schools will travel to Jonesville on Saturday for the annual Sue Carlile tournament.

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Comets, Redskins travel to Reading - The Hillsdale Daily News

Panthers slow down Comets – Kankakee Daily Journal

CLIFTON -- Tuesday night's volleyball game between Manteno and Central was a tale of two teams.

For the Panthers, it was a near-perfect way to kick off the season as they swept the Comets, 25-9 and 25-11, and only seemed to get stronger as the game went on.

For the Comets, it was a step backward in their second contest of the year. Yesterday, Central faced off against Armstrong at the Timberwolf Tip-Off, and though they ultimately lost that game, too, head coach Jill Luckenbill was much happier with their performance in that match.

"They played very well (on Monday), it was a completely different team than what I saw on the court today," Luckenbill said. "Half the girls came to play, half of the girls did not, and that's something that the girls themselves are going to have to change."

Central seemed unsure of itself for the majority of the game, not communicating very well in either set. That resulted in eight dropped balls, one of the main reasons for the lopsided scores.

Manteno took advantage of that hesitancy, jumping out to a 3-0 lead and keeping their foot on the gas. After Central regained their composure after an early timeout, the Comets kept the game close for a few more volleys, but Manteno pulled away on a 5-0 run, and then went on another 9-0 run to end the game.

The second set wasn't much better for Central, though it got off to a much better start than it did in the first one. The Panthers swapped out about half of their roster for the second game, but kept the same momentum going regardless of who was on the court.

Manteno's depth likely will be one of their strong suits this season. The team as a whole is loaded with juniors (eight total), but there's a lot of experience on the roster despite only having four seniors. It helped that the bench was able to contribute significantly in the second game, and senior Madie Monk said she was impressed with how everyone performed in their first game.

"It was nice to see everybody not only getting playing time, but doing well when they were playing too, which is a great factor," Monk said. "We've got great people all up and down the bench. There's not a single person that can't help the team."

As a result, there's some competition going on for roster spots. Manteno coach Cheryl Davis mentioned the team has a few different setters who will be competing for playing time, and both their left and right sides are strong, as well.

"We've got several setters that are doing a nice job running the offense. Couple of juniors and a senior that are kind of battling it out right now, rights and lefts, all the outsides are really fighting for that playing time," Davis said. "It's a great problem to have."

But even though the Panthers have a number of different players who could be game-changers on any given night, there's one in particular who stood out against Central.

Manteno had a dominant lead in the first set, but outside hitter Kaycie Wenzel ended the match decisively with a spike that seemed to rattle the glass in the gym's windows, and that wasn't the only spike of hers with that kind of intensity; she finished with three kills and led the team with seven digs. Though she played just the one set on Tuesday, sitting in the second to allow others more playing time, Davis says that she's one of their top players.

"She brings some consistency. She does a really good job out on that left side swinging and defensively," Davis said. "She's probably the most consistent we have right now, she's just really smart with her swing."

It was a bad game from the beginning for Central, who looked like they were sleepwalking through parts of the match. Call it a bad day or fatigue that carried over from Monday -- Luckenbill wasn't sure what to make of it.

Manteno's fast start and long runs might have contributed to the team's loss; whenever the Panthers accumulated multiple points, the team struggled to find their footing to change the tide.

"That is one thing we struggle with once we're down, we can't catch up," Luckenbill said. "That's our number one goal to have these girls overcome."

It's a younger team for Luckenbill this season, and though some of the players were teammate on the JV squad last season, not many of them have played together. Finding that team chemistry will be key, and how the group responds to this kind of performance might be indicative of what the season looks like for Central.

"All I want to see is the girls to turn around and play like they did yesterday because I know they're capable (of it)," Luckenbill said.

Continued here:

Panthers slow down Comets - Kankakee Daily Journal

Comets JV gridders take good first step – YourGV.com

There was a lot of excitement among the coaches and players on the Halifax County High School junior varsity football team Friday night.

The Comets won their first pre-season test, outscoring Buckingham County High School four touchdowns to none in a scrimmage Friday afternoon at Tuck Dillard Memorial Stadium.

Overall Im pleased, but Im not going to get too far in front of myself, said Comets Head Coach Eugene Turbeville.

I dont want the kids to get too excited early because this was just the first time we matched up against somebody else. It was a good first step, but weve got a lot to work on.

The Comets got a touchdown on a 63-yard run by Shabazz Buster on the fifth play of their first possession of the scrimmage that had both teams run three 10-play series. William Davis snared a pass and raced to a touchdown on a 60-yard scoring play on the ninth play of the Comets second offensive series.

Zyliek Perkins intercepted a Buckingham County High School pass and returned it for a touchdown during the Knights final offensive series and Mekhjay Boyd added the Comets final score on a 67-yard run on the eighth play of the final series.

Along with Davis, Zyliek Perkins and Lamandre Adams also had catches.

At times we ran the ball pretty well, Turbeville pointed out.

We long two long runs from two different running backs. Both quarterbacks (Cody White and Zion Wilson) showed some promise. We werent sure which direction we were going to go. We have been working with both of them. Even though it is a run-based offense, our receivers caught the ball well and ran some decent routes.

As far as the defense went, Turbeville was pretty pleased with his teams effort.

We went primarily with a base defense, Turbeville noted.

We didnt try to do anything too fancy. We didnt want the kids to have to think about too much stuff the first time going out. We ran to the ball pretty well. We tackled pretty well.

We still have other things we need to put in, he added.

The Comets coach said one area the team still needs work is conditioning.

Weve got to get into a little better shape, Turbeville said.

The weather is hot this time of the year, and the kids werent quite ready for that.

The Comets jayvees will get the final pre-season test Thursday in a scrimmage against Colonial Heights High School. The scrimmage is scheduled for 5 p.m. at Halifax County High School.

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Comets JV gridders take good first step - YourGV.com

GAMEFACE 2017: Abington Heights Comets – Scranton Times-Tribune

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Abington Heights Kaleb Sherman during a practice on Monday, August 14, 2017. Christopher Dolan / Staff Photographer

In Joe Repshis tenure as head coach, Abington Heights is among the top programs in the Lackawanna Football Conference.

A year after winning the District 2 Class 5A championship, the Comets aim to maintain that glowing reputation while it rebuilds after losing the majority of the starting team to graduation.

Abington Heights returns only three starters two on offense and one on defense. But that doesnt change the outlook or the approach to the season.

Our goal every day has been to come out and get better, Repshis said. Our focus is to be better every practice. It is a process, but that is always our approach.

Leading the offense is running back Kaleb Sherman, who as a sophomore ran for 536 yards and scored five touchdowns. Fullback Austin Kohut contributed 26 yards rushing last season.

Nate Gronsky, a 6-foot, 245-pound guard, is the only returning lineman for the Comets.

Players expected to contribute along the line of scrimmage include, Chris Callahan at center, Shea Parry and Sage Santarsiero at guard, Joe Makowski, Chris Kane and Tre Kerrigan at tackle.

George Tinsley, who saw action at quarterback and is an All-Region and all-state basketball player, takes over as signal caller. At 6-foot-5, he has size and a strong arm to be an impact player. He passed for 222 yards last season and a touchdown.

Tinsleys receiving group includes John Rama, Chase Overholser, Trey Koehler, another basketball standout, and Corey Perkins.

Defensively, where the Comets were among the best in the LFC, is where the most work must be done. There is only one starter returning, sophomore Mike Malone.

Last season, as a freshman, Malone played like a veteran late and during the playoff run. He finished with 26 tackles with five tackles for loss and a sack.

Matthan Sherman saw a lot of time last year, especially in passing situations. He finished with 26 total tackles with a season-high of six against Valley View.

He also had three interceptions, returning one for a score, in a win over Hazleton Area.

I think we can surprise people, Sherman said. Yes, we did lose a lot of starters, but we have a lot of good athletes and players in this group coming up that maybe nobody really knows about. We have the same goals here and everybody works hard.

Drake, Callahan, Gronsky, Makowski, Santarsiero and Kane will anchor the up front. The linebackers will be Matt Lastauskas, Noah Braid, Kaleb Sherman and Michael Pusateri, and the secondary will feature Matthan Sherman, Rama, Perkins, Overholser, Robby Horvath and Koehler.

Abington Heights must also overcome the loss of starting linebacker Owen Hivner, an All-Region player who had 144 tackles last season. He decided not to play football in his senior year.

We have guys who are returning who experienced a championship season, Repshis said. You cant put a price tag on that. That is something that is always important. You cant simulate in practice those playoff-type plays or playoff situations, so we are encouraging them to speak to the young guys and tell them what it takes and what the expectations are.

Contact the writer: jbfawcett@timesshamrock.com; 570-348-9125; @JobyFawcett26 on Twitter

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GAMEFACE 2017: Abington Heights Comets - Scranton Times-Tribune

Comets hold off Trojans – pharostribune.com

FULTON The Tony Slocum era started off on the right foot Friday night at home when the Caston Comets defeated West Central 13-8 to open their season.

Using a tightly packed double wing offense and a stubborn fly to the ball defense the Comets turned away a determined Trojan squad to claim the win.

Both teams had some success moving the ball in the first half but neither squad could make their way to the end zone. In fact, most of the action in the first half was kept between the 30s and when the teams entered the locker room for halftime the score was still knotted at 0-0.

With less than 5:00 left in the third quarter Caston got its first break of the game. With the ball on the 21-yard line West Central fumbled the ball but recovered on the 6. Forced to punt the ball away the Comets went to work on the 34-yard line. On the fourth play from scrimmage Kasey Ault ran nearside and when he got to the corner he grabbed the back of Dillion Tabler's jersey and followed his blocker into the end zone from 20 yards out at the 2:11 mark to give Caston the lead at 6-0. The point after by Brady Hartman failed.

The football gods were smiling on the Comets following their touchdown. On the first play from scrimmage following the Caston score the Trojans went to the air. To the delight of the Comet faithful the pass missed the intended receiver and instead fell into the arms of Hartman who returned it to the 18-yard line. Three plays later it was Hartman punching it in from 1 yard out at the :27 mark of the third quarter. The PAT by Hartman was good this time and Caston was up 13-0. The score stood heading into the final quarter of play.

The Trojans' only score of the game came on their first possession of the fourth quarter. A 28-yard touchdown pass from Brayden Kletz to Cameron Pratt culminated a nine-play drive at the 9:25 mark. The pass conversion to Pratt looked as if were going to be no good, but as he was being tackled he extended the ball across the goal line and the Comet lead was cut to 13-8.

Forcing a three-and-out by the Comets, West Central went to work again taking nearly seven minutes left on the clock. But surprisingly the Trojans went to the air for incomplete passes on each of their first three downs. The result was three incomplete passes. Facing a fourth-and-long with their punter in the end zone Caston had a nice chance for a safety. Their chances for the safety improved greatly when Pratt fumbled the ball. With the Comet defense closing in on him Pratt escaped and made it to the 43-yard line before being brought down. The Trojan drive stalled after 10 plays before turning the ball over on downs.

Neither team threatened to score after that and Caston took possession of the ball with 1:17 left in the game and ran the clock out for the 13-8 win.

Ault led the Comets with 105 yards rushing on 18 carries. Hartman finished with 66 yards with 18 carries as well.

"It all goes to our lineman. Without them we'd get nowhere when we try to run," Ault said. "We do need to get better and we need to keep conditioning. That has to improve because everybody has to play both ways. Nobody will be coming off the field. We'll enjoy it tonight but tomorrow we'll come in and start over getting ready for next week."

Caston's defense held the Trojans to just 106 yards on the ground and 97 yards through the air.

Ault and Hartman led the defense with five tackles each.

"We had some problems with kids cramping tonight," said Slocum. "We've got to find a way for that to keep from happening. We don't have a lot in the way of number of players so we have to keep them on the field. But even though we're few we're not going to make excuses. We just tried to put pressure on West Central's defense tonight and my hat's off to this group of young men. They played hard tonight and came away with the win."

Originally posted here:

Comets hold off Trojans - pharostribune.com

FOOTBALL: Comets prevail in thriller – Kokomo Tribune

GREENTOWN So many big plays highlighted Easterns first win over Oak Hills football team in five years on Friday night, its hard to pick one that was the brightest in the Comets 31-28 win at Cogdell Field.

But the fourth quarter sure did provide plenty of them.

Trailing the Golden Eagles 21-17 at the start of the fourth quarter, Eastern strung together two scores including a 52-yard Braden Sparks punt return to paydirt and a 62-yard two minute drive that quarterback Garrett Hetzner capped with a one-yard plunge to put the Comets up for good and three great defensive stands, the final one putting a big exclamation mark on the win when junior linebacker Luke Monize sacked Oak Hill quarterback Landry Ozmun on third down to all but seal the win.

I just knew I had to give it my all on that play, Monize said of the sack, which put Oak Hill in a fourth-and-19 situation at the Comet 49 with under :30 to play. An incomplete pass on the following play allowed the Comets to take over on downs and kneel down with :18 to play.

Man, that was incredible, Monize said. Im just proud of the team for stepping up in the situation. Its a great way to start the season.

Despite his big sack, and the play he pointed out from teammates Asher Walden (an interception and sack) and Tyler Hurston and Otis Smith (sacks earlier in the final defensive stand), his favorite moment was Sparks punt return TD, which put Eastern up 24-21 with 6:55 to play.

Definitely that punt return, that was a changer, Monize said. I was shocked honestly. I didnt expect it to happen but Im glad it did.

Oak Hill responded to that score with a with a quick, seven-play drive that went 71 yards as Ozmun found Jonah Powell from four yards out and the Eagles went up 28-24.

The Comets answered that with the 62-yard drive that Hetzner capped with his score less than two minutes later to put Eastern up 31-28.

We gave up the score with under four minutes left and our guys just march it, Comet coach Josh Edwards said. Garrett Hetzners will on the goal line to get that ball in the end zone, just tremendous. We went out and got it. When we had to make those big plays at the end of the game and our defense stiffened up on the pass defense, that was just huge.

Hetzner added a TD run from 13 yards out to cap Easterns opening drive of the night and put the Comets up 7-0. The QB completed 11 of 19 passes for 115 yards on the night, connecting with Elijah Elkins on a 22-yard TD pass in the third quarter to put Eastern up 17-14. VanMatre added a 29-yard field goal with :20 to play in the first half that got Eastern within 14-10 after the Eagles opened went up 14-7 on back-to-back scores.

Sophomore Tytus Morrisett finished with 84 yards on 15 carries to lead Eastern, all of those coming in the second half when he was called upon after Dontae Nolder went out with a knee injury in the first half.

We needed a guy that was going to hit the holes, Edwards said. We were doing okay but we felt like we needed more than three [yards]. And Tytus put his shoulder down and it was a difference maker. This win is a team win because we had so many contributors that stepped in for us.

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FOOTBALL: Comets prevail in thriller - Kokomo Tribune

Comets top Buckingham County HS 34-14 in VHSL Benefit Game – YourGV.com

Halifax County High School Head Football Coach Grayson Throckmorton looked as if the weight of the world had been lifted from his shoulders.

All of the hard work the Comets players and coaching staff had put in over the spring and summer months learning and teaching the new offensive and defensive schemes that are being implemented for this season finally saw some reward.

The Comets broke on top early and topped Buckingham County High School 34-14 Friday night at Tuck Dillard Memorial Stadium in the annual Virginia High School League Benefit Game.

"It's a huge relief because you don't know how they (the players) are going to perform under the first game-like situation," Throckmorton explained.

"In practice, after you've been beating on each other and you're getting frustrated and make mistakes, as a coach you're always worried to death about how you're going to respond. I thought we responded really well."

The Comets jumped on top in their first possession of the game with quarterback Ryan Moore scoring on a 10-yard run with 6:02 left in the first quarter to cap a seven-play, 44-yard drive. Ben Harris added the extra point to put the Comets up 7-0.

Comets senior running back Jamal Brandon scored the first of his two touchdowns in the game on a 64-yard run with 6:49 left in the first half on his team's fourth possession of the half. Harris' kick put the Comets up 14-0.

Darrius Bowman scored on a 33-yard run with 6:37 left in the third quarter on the Comets' second possession of the second half, and Harris added the extra point to extend the Comets' lead to 21-0.

Buckingham County High School followed with its first touchdown of the game, a score that came on a 10-yard run by Walter Edwards with 4:09 left in the third quarter. The Comets immediately answered with Brandon breaking free for a 61-yard scoring run with 2:59 left in the third quarter. A kick by Harris made the score 28-7.

The Knights scored their final touchdown on a 1-yard run by Gerry Toney with 4:21 left in the game to make it a two- touchdown Comets spread at 28-14.

Halifax County High School capped the game with Corey Brandon intercepting a pass from Toney and returning it 85 yards for a touchdown as time expired on the clock. That score gave the Comets the final 20-point margin.

Not only did the Comets score five touchdowns in the game, they played well on the defensive side of the ball as well. The Comets intercepted three Buckingham County High School passes, with Amir Spencer, Brandon Davis and Corey Brandon doing the honors, with Brandon returning his pick for a touchdown.

While there was a lot of good to be seen, there were also some miscues.

The Comets turned the ball over three times, twice on interceptions and once on a lost fumble. Also, the Comets were bitten by several penalties, two of which negated touchdowns, and one resulted in a long run by Jamal Brandon being called back.

Brandon had a 13-yard touchdown run nullified due to a penalty and a punt return for a touchdown by Kenneth Davis was called back due to a penalty.

"The only thing I was very disappointed in about tonight is that in my style of offense and what we do, turning the ball over three times and having 11 penalties is not going to get it done because you have big runs and so forth get called back," Throckmorton.

"Our goal is to hold onto the ball and cut our mistakes down and our penalties down. If we do that, we will be a little more efficient."

The Comets will get their final pre-season test Thursday night when they host Colonial Heights High School in a scrimmage at Halifax County High School.

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Comets top Buckingham County HS 34-14 in VHSL Benefit Game - YourGV.com

Sulphur sweeps Madill; DHS Lady Comets sink Lexington at home – Daily Ardmoreite

If there was ever a team who is flying under the radar this season, its the Sulphur Lady Bulldogs.

If there was ever a team who is flying under the radar this season, its the Sulphur Lady Bulldogs.

Monday afternoon, Heath Gilberts squad decided to make a little more noise in the district 3-4A standings as SHS hosted Madill in a doubleheader.

Sulphur had no problems handling the Lady Wildcats as they won 12-0 and 13-1, improving them to 8-1 overall and 4-0 in district play.

Madill meanwhile fell to 2-8 overall and 0-4 in district play.

Today will see a showdown take place between the Lady Bulldogs and the Lone Grove Lady Horns, as both teams sit at 4-0 atop district 3-4A. First pitch is set for 5 p.m from the Sulphur softball complex.

Madill meanwhile will be hosting Pauls Valley today in a double header beginning at 5 p.m.

Dickson 5 Lexington 3

Coming off a 1-2 weekend at the Tishomingo Tournament, the Dickson Lady Comets got back in the win column Monday against the Lexington Lady Bulldogs.

LHS got a run in the second and fourth innings, before Dickson came back with five in the bottom half of the fourth inning.

First Kelsie Allen registered an RBI single, before Savannah Hunley put Dickson in front when she cleared the bases with a three-RBI triple to center field, putting the Lady Comets ahead 4-2.

Kylie Farmer then gave Dickson an insurance run with a sacrifice fly RBI.

Lexington threatened to rally with one run in the sixth, but the Lady Comets snuffed it out.

Shanna McKown threw a complete game on the mound, allowing two earned runs on 10 hits with one walk and four strikeouts.

Dickson (3-3) is at Tishomingo today with first pitch set for 5 p.m.

Caddo 4 Tishomingo 2

Speaking of the Lady Indians, their normal high flying offense was held in check on Monday at home by Caddo.

CHS took the lead 1-0 in the top of the third, before the Lady Indians tied the game with a run in the bottom of the third thanks to an RBI double from Grace Anderson to left.

It looked as though the Lady Indians home magic was going to strike again as Cheyenne Arkansas gave Tishomingo a 2-1 lead in the bottom of the fifth with an RBI single to center.

However, three runs in the top of the sixth by Caddo snapped the Lady Indians three-game winning streak.

Anderson took the loss on the mound for Tishomingo throwing a complete game effort. She allowed two earned runs on five hits with two walks and 12 strikeouts.

Kylee Anderson got the win in the circle for Caddo, also throwing a complete game effort. She allowed two earned runs on seven hits with two walks and four strikeouts.

Tishomingo (8-3) is at home today against Dickson.

Healdton 11 Wilson 3 F/6

Following a rough weekend at the Oklahoma Shootout, the Healdton Lady Bulldogs snapped their five game losing streak with a six inning run-rule win over the Wilson Lady Eagles Monday at Lady Bulldog Field.

HHS got on the board in the second when Josey Brooks slapped an RBI double which scored Jessie Black.

The lead was increased in the third inning when Adrie Brown scored a run, followed by a three-RBI double from Whisper Love, which put the Lady Bulldogs up 5-0.

Wilson finally struck back in the top of the fourth when Taylor Wolf hit an RBI single to center, making it 5-1.

Courtney Schiralli made it 5-2 in the fifth when she scored for the Lady Eagles.

However, Healdton was in no mood to let a comeback happen this time.

Tori Wingo and Macey Howell each scored to make it a 7-2 ball game, while Brown scored following an error to make it 8-2.

WHS tried to mount one last rally in the top of the sixth when Katelyn Hacker slapped an RBI single to score Wolf, but the Lady Bulldogs added three in the bottom half of the inning with Tori Wingo, Brooks and Love scoring to finish the game.

Mollie Marshall got the win in the circle for the Lady Bulldogs, while Destiny Colbert took the loss for the Lady Eagles.

Healdton (2-5) is at Stratford today beginning at 5 p.m. while Wilson (4-3) is hosting Ryan at 4:30 p.m.

Kingston 11 Colbert 0 F/4

Kingstons Lady Redskins made themselves feel right at home on the road Monday afternoon.

Four innings was enough for KHS to run-rule Colbert, as the Lady Redskins won for the third time in their last four games.

Madison Auld got Kingston on the board with an RBI single in the top of the first, before Dana Wagnon doubled the lead with a sacrifice fly RBI in the second.

Auld struck again in the second as she hit a three-RBI double to center field, making it a 5-0 Lady Redskins lead.

Jewell Henery put KHS up 6-0 in the second with an RBI single to right.

Wagnon got another pair of RBIs in the third with a double to center, with Taylor Spence hitting a sacrifice fly RBI to make it 9-0.

Auld got yet another RBI hit as she sent a single to left field, putting the Lady Redskins in double digits.

Madison Jones finished the scoring with an RBI single in the fourth.

Spence got the win on the mound for Kingston, throwing four innings of work. She allowed just one hit with one walk and three strikeouts.

Kingston (5-4) will be at Davis this evening as part of a triangular with the Lady Wolves and Washington.

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Sulphur sweeps Madill; DHS Lady Comets sink Lexington at home - Daily Ardmoreite

Golden, Comets win Tryba Preseason Tournament – Sports … – Standard Speaker

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SUBMITTED PHOTO Hazleton Area freshman Joey Rebarchick retrieves his hole-in-one ball out of the cup on No. 11 at Fox Hill Country Club on Monday. Rebarchick was playing his first varsity match for the Cougars, competing in the annual Ted Tryba Tournament when he carded the ace. Rebarchick finished with an 82 and secured a spot in the pre-district tournament with his opening-day effort.

WARREN RUDA / STAFF PHOTOGRAPHER Crestwoods Shane Angle tees off on the second hole at Fox Hill Country Club Monday during the annual Ted Tryba Tournament.

EXETER Mike Golden has come a long way in three years playing golf.

Inspired by his grandfather plus former Crestwood teammate Tyler Papura, Golden tried the sport two years ago as a sophomore, when merely carding 50 over nine holes was a success.

But, then, he got really good, even tying a school record with a 2-under 34 last year at Blue Ridge Trail Golf Club.

Golden couldnt have asked for a better start to his senior year Monday, when he shot a 1-over 72 and won the Tryba Preseason Tournament at Fox Hill Country Club.

Doubled, tripled my practice time, Golden said, explaining the rapid improvement in his game. Even if its raining and I dont go to the driving range, Im out in my yard chipping around, setting up targets.

Goldens round was highlighted by a pair of birdies against three bogeys and strong putting, as well as a handful of saves to work himself out of the woods.

Length is No. 1. He hits the ball a long way, which is good, Crestwood coach

Mark Jarolen said of Golden. His short game has improved dramatically. So its all about and we stress it all the time putting the ball in the hole. Hes started doing a really good job at that.

Goldens first-place finish comes after tying for 10th and 12th place as a junior and sophomore, respectively.

In addition to Goldens 72, junior Jeremy Harper (73), senior Shane Angle (75) and junior C.J. Bono (79) helped shoot the Comets to a team title, their third in the last four years.

With a team score of 299, Crestwood became the first team to break 300 since Holy Redeemer shot 298 in 2013, a season that ended with a state championship for the Royals.

I was impressed, Jarolen said. But they play a lot of golf and they work hard and are very capable. They just put it all together at one time, which is great.

Harpers 73 landed him in a tie for second place with Dallas senior Mason Gattuso, who was the WVCs only district champion a year ago.

Dallas Brett Ostroski shot a 74 for fourth place, while Angle finished fifth.

Other highlights included Hazleton Area freshman Joey Rebarchick in his first-ever varsity event making a hole-in-one on par-3 No. 11. The Cougars finished fourth as a team at 331, with Jordan Pick (76) tying for sixth place. Pick and Cougar teammates Rebarchick (82), Matt Boretski (84) and Brian Bartel (89) all secured a spot in the pre-district tournament with their efforts on Monday.

MMI, which finished sixth out of 14 teams at 338, was led by George Palermo, who tied for ninth with a 78. Jessica McClellan tied for 17th at 80, followed by Morgan Long (88) and Zack Young (92).

Perhaps the biggest takeaway, though, was that the WVC golf scene appears to be in better shape today than it was following last years Tryba.

Last year, Dallas won the team championship with a 321, a score that this time around would have finished after Crestwood (299), itself (304) and Holy Redeemer (318).

Plus, only nine players last year shot 80 or below, a number that was doubled with 18 such finishers this year.

The WVC will waste no time in getting right to the thick of competition now, as Crestwood will host Dallas on Wednesday in a showdown of the top-two Tryba finishers.

Contact the writer: mbufano@citizensvoice.com; 570-821-2060; @CVBufano on Twitter

Schuylkill League

Pine Grove 354

Marian 376

Luke Reiters medalist round of 80 at Blue Mountain powered Pine Grove past visiting Marian.

Nate Hartman checked in with an 86, Austin Dubbs shot 92, and Karson Felty added a 96 for the Cardinals.

Jacob Artz (82) and Nick Kurzinsky (85) showed the way for the Colts (2-1). Collin McCarrie had a 101 and Lucca Stoia finished at 108.

Nativity 387

Weatherly 426

At Schuylkill Country Club, Tyler Coyle shot a blistering 71 to run away from the field and lead Nativity past visiting Weatherly.

Ty Daubert (94), Joe Manus (108) and Jack Piccioni (114) rounded out the Hilltoppers scoring.

For Weatherly (0-3), Ashton Gerhard had a 101, followed by AJ Knepper (104), Ryan Fairchild (109) and Jared Zaremba (112).

Mahanoy Area 376

North Schuylkill 444

At Mountain Valley, Josh Jacavage took medalist honors with a 90, leading a balanced Mahanoy Area attack against visiting North Schuylkill.

Tyler McCole (91), Kathryn McCarthy (96) and Will Conroy (99) all joined Jacavage in the 90s for the Golden Bears.

Blake Rothermel paced the Spartans with a 103, with Kris Wolfe (107), Kevin Kovach (119) and Brandon Lucas (115) rounding out the scoring.

H.S. Girls Tennis

Schuylkill League

Jim Thorpe 4

Tamaqua 1

Brooke Williams outlasted Leanne Van Essendelft 6-3, 7-6 (8) at first singles to give Tamaqua its lone team point in Mondays season-opener at Jim Thorpe.

Christy McLean defeated Alexis Breiner 6-1, 6-4, and Kaitlyn ONeil downed Molly Clemson 6-3, 6-1 to give Jim Thorpe two points in singles play.

The Olympians wrapped up the match with a sweep of the doubles contests. At first doubles, Angelica Uzar and Evelyn Flores blanked Tamaquas Madison Wickersham and Emily Fisher (6-0, 6-0), and at No. 2 doubles Chloe Getz and Triselle Samuels teamed up to beat Sabrina Moyer and Jocelyn Rega (6-1, 6-0).

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Golden, Comets win Tryba Preseason Tournament - Sports ... - Standard Speaker


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