Daily Archives: May 20, 2017

Quasars are extremely bright, extremely distant objects. They are the disks of material around supermassive black holes, which heat up and glow as material streams inward toward the event horizon. And now, the Sloan Digital Sky Survey (SDSS)has identified more than 147,000 of these objects in the distant universe to create a first-of-its-kind 3-dimensional map of the early universe that is also the largest such map available to date.

The observations were taken over the course of two years as part of the SDSS Extended Baryon Oscillation SpectroscopicSurvey, abbreviated eBOSS, which uses the Sloan Foundation 2.5m Telescope at Apache Point Observatory. eBOSS aims to more accurately measure the expansion history of the universe. The quasars in the study were spotted shining at a time when the universe was between 3 and 7 billion years old.

This new, more complete map of the universe and its expansion history agrees with the standard cosmology astronomers have developed over the past two decades and are currently using today, which includes properties such as Einsteins general theory of relativity and the existence of dark matter and dark energy.

Studying this time frame is particularly important because its the epoch leading up to when the universes expansion changed from a decelerating to an accelerating expansion. That happened when the universe was roughly 7.8 billion years old, or about 6 billion years ago. Today, that acceleration continues in short, objects farther away from us are receding faster, and continue to do so because of a cosmological component called dark energy. Characterizing the exact nature of this transition from a decelerating to accelerating universe can place further constraints on the nature of dark energy, which is the dominant component in our universe at the present time.

In a recent press release, Will Percival, a professor of cosmology at the University of Portsmouth and the eBOSS survey scientist, explains, Even though we understand how gravity works, we still do not understand everything there is still the question of what exactly dark energy is. We would like to understand dark energy further.

eBOSS is looking into the nature of dark energy by studying baryonic acoustic oscillations, or BAOs. BAOs are the remnant signature of sound waves traveling through the very early universe; when the universe was about 380,000 years old, these sound waves were essentially frozen in place by changing conditions. Since then, their signature has been stretched by the expansion of the universe. But astronomers have a good idea of what the BAOs should have looked like at the time they were frozen, making the changes we see in BAOs over time a clear record of the universes expansion over time.

Thus, BAOs can be used as a sort of standard ruler by cosmologists. The size of the oscillations corresponds to the most likely distance between galaxies, including the quasars that reside within them. According to Pauline Zarrouk, a PhD student at the University Paris-Saclay, You have metres for small units of length, kilometers or miles for distances between cities, and we have the BAO for distances between galaxies and quasars in cosmology.

Today, the distribution of galaxies (and their quasars) is a reflection of the frozen-in BAOs, so the better we can map the universe, the better we can understand how its expansion has changed over time, independent of other ways of measuring that expansion, such as using supernovae or lensed quasars.

Thus far, Our results are consistent with Einsteins theory of general relativity says Hector Gil-Marin of the Laboratoire de Physique Nuclaire et de hautes nergies in Paris. Gil-Marin is one of the astronomers who contributed to the analysis of the quasars and the creation of the map. We now have BAO measurements covering a range of cosmological distances, and they all point to the same thing: the simple model matches the observations very well.

See the article here:

Astronomers create the largest map of the universe | Astronomy.com - Astronomy Magazine

Theres a star 1,300 light years away that has exhibited some of the strangest behavior ever seen: something dims 20 percent of its light, something that is beyond the size of a planet. Its called KIC 8462852, but most people shorthand it Tabbys Star, or Boyajians Star for its discoverer, Tabitha Boyajian.

Heres the thing, though. Absolutely nobody knows why its dimming that much. It could be a massive fleet of comets or the debris of a planet. But its not giving off much infrared excess, which is a sort of "heat glow" from reflected starlight. And now, it seems to be dimming again, either helping or complicating the search for a solution.

Boyajian and co-investigator Jason Wright first put out the alert, hoping to garner observations from telescopes worldwide. Theyre hoping at least one of telescope can grab spectra from the star to see what is causing the dimming.

So far the dimming is at 2-3 percent, meaning the transit of something is just starting. Tabbys Star has a dedicated telescope waiting to find such an event, so the big observation period could yield further clues to whats occurring.

Ok, its time we tell you: some people think its aliens. The hypothesis, put forth by Wright, states that in the absence of a good hypothesis, all avenues must be explored, and that includes giant Dyson Swarm machines harnessing the power of the star. Gathering the spectra could help rule that out or bolster the case for that all other avenues exhausted scenario.

Heres the thing, too: you can get in on the action. Amateur astronomers use smaller scopes to track the star, which is bigger and older than the Sun. Its at around 12th magnitude in the direction of Cygnus. So get out there tonight and hunt for some aliens.

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The weird star that totally isn't aliens is dimming again | Astronomy ... - Astronomy Magazine

Composite image of the Fomalhaut star system. The ALMA data, shown in orange, reveal the distant and eccentric debris disk in never-before-seen detail. The central dot is the unresolved emission from the star, which is about twice the mass of our sun. Optical data from the Hubble Space Telescope is in blue; the dark region is a coronagraphic mask, which filtered out the otherwise overwhelming light of the central star. Credit: ALMA (ESO/NAOJ/NRAO), M. MacGregor; NASA/ESA Hubble, P. Kalas; B. Saxton (NRAO/AUI/NSF)

An international team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) has made the first complete millimeter-wavelength image of the ring of dusty debris surrounding the young star Fomalhaut. This remarkably well-defined band of rubble and gasis likely the result of exocomets smashing together near the outer edges of a planetary system 25 light-years from Earth.

EarlierALMA observations of Fomalhaut taken in 2012 whenthe telescope was still under construction revealed only about one half of the debris disk. Though this first image was merely a test of ALMAs initial capabilities, it nonetheless providedtantalizing hints about the nature and possible origin of the disk.

The new ALMA observations offer a stunningly complete view of this glowing band of debris and also suggest that there are chemical similarities between its icy contents and comets in our own solar system.

ALMA has given us this staggeringly clear image of a fully formed debris disk, said Meredith MacGregor, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and lead author on one of two papers accepted for publication in theAstrophysical Journaldescribing these observations. We can finally see the well-definedshape of the disk, which may tell us a great deal about the underlyingplanetary systemresponsible for its highly distinctive appearance.

Fomalhaut is a relatively nearby star system and one of only about 20 in which planets have been imaged directly. The entire system is approximately 440 million years old, or about one-tenth the age of our solar system.

As revealed in the new ALMA image, a brilliant band of icy dust about 2 billion kilometers wide has formed approximately 20 billion kilometers from the star.

Debris disks are common features around young stars and represent a very dynamic and chaotic period in the history of a solar system. Astronomers believe they are formed by the ongoing collisions of comets and other planetesimalsin the outer reaches of a recently formed planetary system.The leftover debris from these collisions absorbs light from its central star and reradiates that energy as a faint millimeter-wavelength glow that can be studied with ALMA.

Using the new ALMA data and detailed computer modeling, the researchers were able to calculate the precise location, width, and geometry of the disk. These parameters confirm that such a narrow ring is likely produced through the gravitational influence of planets in the system, noted MacGregor.

The new ALMA observations are also the first to definitively show apocenter glow, a phenomenon predicted in a 2016 paper by Margaret Pan, a scientist at the Massachusetts Institute of Technologyin Cambridge, who is also a co-author on the new ALMA papers. Like all objects with elongated orbits, the dusty material in the Fomalhaut disk travels more slowly when it is farthest from the star. As the dust slows down, it piles up, forming denser concentrations in the more distant portions of the disk. These dense regions can be seen by ALMA as brighter millimeter-wavelength emission.

Using the same ALMA dataset, but focusing on distinct millimeter-wavelength signals naturally emitted by molecules in space, the researchers also detected vast stores of carbon monoxide gas in precisely the same location as the debris disk.

These data allowed us to determine that the relative abundance of carbon monoxide plus carbon dioxide around Fomalhaut is about the same as found in comets in our own solar system, said Luca Matr with the University of Cambridge, UK, and lead author on the teams secondpaper. This chemical kinship may indicate a similarity in comet formation conditions between the outer reaches of this planetary system and our own. Matr and his colleaguesbelieve this gas is either released from continuous comet collisions or the result of a single, large impact between supercomets hundreds of times more massive than Hale-Bopp.

The presence of thiswell-defined debris disk around Fomalhaut, along with its curiously familiar chemistry, may indicate that this system is undergoing its own version of the Late Heavy Bombardment, a period approximately 4 billion years ago when the Earth and other planets were routinely struck by swarms of asteroids and comets left over from the formation of our solar system.

Twenty years ago, the best millimeter-wavelength telescopes gave the first fuzzy maps of sand grains orbiting Fomalhaut. Now with ALMAs full capabilities the entire ring of material has been imaged, concluded Paul Kalas, an astronomer at the University of California at Berkeley and principal investigator on these observations. One day we hope to detect the planets that influence the orbits of these grains.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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[ 19 May 2017 ] Icy ring around Fomalhaut observed in new wavelength News - Astronomy Now Online

2007 OR10 is the largest body in the solar system with no common name. And now, the no-name dwarf planet with a diameter between 800 and 950 miles (1,2901,528km) has been discovered to have a moon.

As the name implies, 2007 OR10 was initially discovered in 2007. Its the third or fourth largest object in the Kuiper Belt, just after Pluto, Eris, and Makemake. There is some debate as to its size. Dwarf planet planetary scientist Mike Brown lists it as the fourth largest, while other estimates place it above Makemake in diameter. Browns graduate student at the time, Meg Schwamb, discovered the world. It is a bright, red, icy world that swings from 33 to 101 AU in its orbit. (One AU is the distance between the Earth and the Sun, and Neptune is at 30 AU.)

OR10 has a very slow rotation rate, which hid the moon in plain sight from Hubble for quite some time. Its a large moon for OR10s size, estimated at 150 to 250 miles (240400km) in diameter. The higher estimate places the moon at the lower limits of dwarf planet status, had it orbited the Sun on its own. A body is considered a dwarf planet if it can attain a round shape and is only in orbit around the Sun and not another body. The moon is about one-quarter the size of OR10, a similar ratio to the Moon and Earth.

So now theres a dwarf planet without a name with a fairly large moon around it. Maybe this boosts the case for giving it a real name.

Excerpt from:

Researchers find a tiny moon around a large unnamed dwarf planet - Astronomy Magazine

This image of Jupiter was taken on 3April 2017 when the planet was at a distance of 414million miles (667million kilometres) from Earth. The NASA/ESA Hubble Space Telescope reveals the intricate, detailed beauty of Jupiters clouds as arranged into bands of different latitudes. Lighter coloured areas, called zones, are high-pressure where the atmosphere rises. Darker low-pressure regions where air falls are called belts. Constantly stormy weather occurs where these opposing east-to-west and west-to-east flows interact. The planets Great Red Spot (GRS, lower left), is a long-lived storm roughly the diameter of Earth. Oval BA, affectionately referred to as the Little Red Spot (lower right), transits roughly 90minutes ahead of the GRS. Image credit: NASA, ESA, and A. Simon (GSFC).Observers in the heart of the British Isles have already entered that time of the year when astronomical twilight lasts all night. But even if the sky never truly gets dark, take solace in the sight of Jupiter, currently highest in the sky to the south around 10pmBST.

The Solar Systems largest planet is now seven weeks past opposition, but still presents a magnitude-2.3 disc with an angular width of 42arcseconds. This is means that a telescope magnification of just 45 is sufficient to enlarge it to the same apparent size of an average full Moon as seen with the unaided eye.

Even the smallest telescope (and powerful binoculars, if suitably steadied) will reveal Jupiters four largest Galilean moons Io, Europa, Ganymede and Callisto in their orbital dance around their parent planet.

With a quality telescope of 3-inch (7.6-cm) aperture or greater at magnifications of 100 and more you can occasionally observe (subject to good seeing conditions) the shadows of these moons slowly drift slowly across the face of Jupiter, like ink-black dots. The timings of the start and end of such events visible from the UK for the remainder of the month are tabulated below. The times that the moons themselves are occulted (hidden) by Jupiter, or pass into or emerge from the planets shadow (eclipsed) are also shown.On the UK morning of Sunday 28May 2017, the shadows of Jupiters Galilean moons Io and Ganymede may be seen simultaneously on the face of their parent planet from 1:16am to 1:39amBST. This computer simulation depicts the scene at 1:20amBST. Note that this is an erect-image view (north up, east left). Users of Newtonian/Dobsonian telescopes should rotate this image 180degrees to match the eyepiece view, while owners of refractors, Maksutov- and Schmidt-Cassegrain telescopes with a star diagonal should mirror the image left to right. AN graphic by Ade Ashford/SkySafari.Great Red Spot and OvalBA (aka Little Red Spot) Jupiters Great Red Spot (GRS) also puts on an appearance at times suitable for observing from the UK during the remainder of the month, also shown in the table below. The GRS is said to transit when it lies on an imaginary line joining Jupiters north and south poles. Owing to the planets fast rotation (at the latitude of the Great Red Spot it takes little more than 9h55m to make one revolution), the GRS is well seen for roughly an hour either side of the transit time. The Great Red Spot has an unmistakable brick red hue at present, making it an easy object to identify in quality telescopes capable of 100 magnification or more when seeing conditions are good.

For observers with 8-inch (20-cm) and larger telescopes, try to see the smaller OvalBA (also shown in the image at the top of the page), popularly known as the Little Red Spot though do bear in mind that it transits the central meridian of Jupiter around 1hours before the times given for the GRS.Predictions for the start and end times of Galilean shadow transits, plus information on their eclipses and occultations for any given date in a slightly more user friendly format may also be obtained through our Almanac. To see the satellite events for any given day, ensure that the Add phenomena of Jupiter? checkbox is ticked. Like the Great Red Spot predictions, all Galilean moon phenomena events are in Universal Time (UT). For help using the Almanac, see this article.

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Don't miss Jupiter's moons and Great Red Spot during May - Astronomy Now Online