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The Evolutionary Perspective
Category Archives: Astronomy
Posted: October 27, 2019 at 2:50 pm
Now, a team of astronomers has spotted one of these early galaxies in the act of churning out stars. Their observations capture the galaxy, which is about the size of the Milky Way, as it was about 1 billion years after the Big Bang. However, the galaxy is creating roughly 300 Suns worth of stars per year, while the Milky Way forms just one or two solar masses of stars each year.
The team says their find is something of a cosmic yeti because astronomers previously dismissed the idea that such monster early galaxies ever existed.
The researchers reported their find Tuesday in The Astrophysical Journal.
The researchers looked at other images of this patch of sky and discovered faint traces of the galaxy in various wavelengths of light. Those traces by themselves were too faint for anyone to be sure there was a galaxy there. But combined with the much clearer and brighter ALMA data, the researchers could be more confident that those traces of light came from the same galaxy. From the traces of light the researchers gathered, they were able to infer how fast the galaxy is building up its store of stars.
Because the researchers stumbled upon the galaxy by accident in a fairly small patch of sky, they believe these quickly star-forming galaxies arent rare.
The fact that weve been able to find one object and that its relatively common that makes me excited for future surveys, Williams said. Hopefully, we will find more, and then well be able to measure the formation histories of these things better with future data.
The newly discovered galaxy is part of the puzzle of how such massive galaxies formed so early in the universe. Before long, Williams hopes, astronomers will find more pieces of the puzzle and create a more complete picture of galaxies throughout the universes history.
Posted: at 2:50 pm
Sunday, October 27Uranus reaches opposition and peak visibility tonight. Opposition officially arrives at 4 a.m. EDT on the 28th, when the outer planet lies opposite the Sun in our sky. This means it rises at sunset, climbs highest in the south around 1 a.m. local daylight time, and sets at sunrise. (From 40 north latitude, Uranus peaks at an altitude of 63, the highest it has appeared at opposition since February 1962.) The magnitude 5.7 planet lies among the background stars of southern Aries. In the nights around opposition, you can find it 3 south-southwest of the similarly bright star 19 Arietis.. Although Uranus shines brightly enough to glimpse with the naked eye under a dark sky, use binoculars to locate it initially. A telescope reveals the planets blue-green disk, which spans 3.7". To learn more about viewing Uranus and its outer solar system cousin, Neptune, see Observe the ice giants in Octobers Astronomy.
New Moon occurs at 11:38 p.m. EDT. At its New phase, the Moon crosses the sky with the Sun and so remains hidden in our stars glare.
Monday, October 28Although the Orionid meteor shower peaked last week, the shower remains active until November 7. And with the Moon now gone from the night sky, observers can expect to see a few shooting stars in the predawn sky. To differentiate an Orionid from a sporadic, remember that a shower meteor will appear to radiate from the northern part of the constellation Orion the Hunter.
Tuesday, October 29The solar systems two inner planets appear near each other in the early evening sky. Tonight, Mercury slides 3 due south (lower left) of Venus. You can find the pair with the help of a two-day-old crescent Moon. Our satellite stands 8 high 30 minutes after sunset with Venus 5 to its lower right and Mercury 6 directly below the Moon. All three objects should just fit in the field of view through 7x50 binoculars. At magnitude 3.8, Venus shines far brighter than magnitude 0.1 Mercury.
Wednesday, October 30This week offers an excellent opportunity to view the zodiacal light. From the Northern Hemisphere, early autumn is the best time of year to observe this elusive glow before sunrise. It appears slightly fainter than the Milky Way, so youll need a clear moonless sky and an observing site located far from the city. Look for the cone-shaped glow, which points nearly straight up from the eastern horizon, shortly before morning twilight begins (around 6 a.m. local daylight time at mid-northern latitudes). The Moon remains out of the morning sky until November 11, when its bright light will return and overwhelm the much fainter zodiacal light.
Thursday, October 31Use the waxing crescent Moon as a guide to finding Jupiter in the southwestern sky this evening. You can find Jupiter 5 to Lunas lower right as darkness falls. Of course, Jupiter is on display all week. It shines at magnitude 1.9 and dominates the early evening sky from its perch in southern Ophiuchus the Serpent-bearer. When viewed through a telescope, Jupiter shows a 33"-diameter disk with striking details in its dynamic atmosphere. You also should see four bright points of light arrayed around the planet: the Galilean moons Io, Europa, Ganymede, and Callisto.
Friday, November 1The Moon moves about 13 eastward relative to the background stars each day, and this movement carries it into Saturns vicinity this evening. Look for the ringed planet 4 to Lunas upper left. As with Jupiter, Saturn remains a glorious sight all week. The ringed planet resides among the background stars of Sagittarius the Archer, a region that appears 20 high in the southwest as twilight fades to darkness and doesnt set until 10 p.m. local daylight time. Saturn shines at magnitude 0.6 and appears significantly brighter than any of its host constellations stars. Although a naked-eye view of the planet is nice, seeing it through a telescope truly inspires. Even a small instrument shows the distant worlds 16"-diameter disk and spectacular ring system, which spans 36" and tilts 25 to our line of sight.
Saturday, November 2After a three-month hiatus, Mars returns to view before dawn this week. You can find it 8 above the eastern horizon an hour before the Sun rises. The Red Planet shines at magnitude 1.8 and should be obvious through binoculars. Once you find the ruddy world, try to spot it with just your naked eye.
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Posted: at 2:50 pm
This artist's impression of an early, massive galaxy that forms from the merger of... [+] smaller-protogalaxies shows how it should be obscured by dust during the most rapid phases of star-formation. For the first time, a team of astronomers may have discovered the missing link between the earliest and the later, more massive galaxies that we see.
One of the greatest challenges for a scientist is that every time you make a new advance, it only raises more questions. When we look out at our Universe today, we see galaxies with all sorts of different properties. We see giant ellipticals that haven't formed stars in billions of years; we see Milky Way-like spirals that are rich in heavy elements; we see irregular galaxies; we see dwarf galaxies; we see ultra-distant galaxies that appear to be forming stars for just the first or second time.
But when you put this all together, there are some puzzles. Some galaxies have grown to be so large soearly that they've defied a coherent explanation. With only small, low-mass galaxies found at great distances by Hubble, the active formation of a large galaxy has long been astronomy's missing link. With a new discovery of a dark, massive galaxy, astronomers may have just cracked the mystery, and solved a longstanding cosmic puzzle.
Galaxies comparable to the present-day Milky Way are numerous, but younger galaxies that are Milky... [+] Way-like are inherently smaller, bluer, more chaotic, and richer in gas in general than the galaxies we see today. For the first galaxies of all, this ought to be taken to the extreme, and remains valid as far back as we've ever seen. There is an unexplained gap between the earliest proto-galaxies and the first large galaxies that astronomers have struggled to explain.
To understand how galaxies form and grow up in our Universe, it's always best to start at the very beginning. Cosmologists have assembled a comprehensive and coherent picture of the Universe, and if we trace out how that Universe evolves and grows from its humble beginnings to the cosmos we inhabit today, we should be able to come up with a story that tells us what we ought to see.
The Universe, in the aftermath of the Big Bang (post-inflation), arrives on the scene with the seeds for our modern-day galaxies already planted. Our Universe is hot, dense, expanding, and filled with matter, antimatter, dark matter and radiation. It's also born almost perfectly uniform, but with tiny density imperfections in it. On all scales, the densest regions are just a few parts-in-100,000 denser than average, but that's all the Universe needs.
The largest-scale observations in the Universe, from the cosmic microwave background to the cosmic... [+] web to galaxy clusters to individual galaxies, all require dark matter to explain what we observe. The large scale structure requires it, but the seeds of that structure, from the Cosmic Microwave Background, require it too.
As the Universe expands and cools, the regions that have slightly more matter (normal and dark combined) than others will begin to preferentially attract more and more of the matter from surrounding regions towards it. As time goes on, radiation becomes less important, and these matter imperfections can grow at a faster rate as they continue to grow in density.
Although it takes somewhere between 50 and 100 million years for the very first region in the Universe to become dense enough to form stars, that's just the start of the story. These first stars, once they start turning on, herald the arrival of energetic, ultraviolet photons that start streaming through the Universe. Over time, as stars form in more and more locations, the neutral atoms throughout space begin to be reionized, as the Universe slowly becomes transparent to visible light.
The most distant galaxy ever discovered in the known Universe, GN-z11, has its light come to us from... [+] 13.4 billion years ago: when the Universe was only 3% its current age: 407 million years old. But there are even more distant galaxies out there, and we all hope that the James Webb Space Telescope will discover them.
At around 200-250 million years after the Big Bang, the first galaxies begin to form, increasing the rate of reionization as star-forming regions cluster and merge together. The earliest galaxy we've ever identified (with today's instrumentation limits) appears about 400 million years after the Big Bang, with all the earliest galaxies actively forming stars at an alarming rate, but no more massive than 1% the mass of our modern Milky Way.
After a total of 550 million years, the Universe finally becomes fully reionized, and light can freely travel without being absorbed. Yet we continue to see only these bright but low-mass galaxies for some time, until about a billion years after the Big Bang, when enormous galaxies even more massive than our Milky Way appear in our telescopes. The big puzzle here is the missing link between these two populations.
In theory, the way these cosmic structures should form is through gravitational growth and mergers. Individual proto-galaxies should attract the matter from surrounding regions of space, while different proto-galaxies should attract one another. As time goes on, the gravitational influence of the various galaxies starts to affect larger and larger scales, leading to galaxies growing by eating one another and merging together.
But if that were the case, we wouldn't expect to see only the small, early proto-galaxies and the large, mature, post-merger galaxies. We would expect to see that intermediate stage, where the proto-galaxies are merging together, during the growth phase where star-formation is actively occurring. But all of the early galaxies we've seen aren't forming stars at a fast enough rate to explain these mature galaxies.
The distant galaxy MACS1149-JD1 is gravitationally lensed by a foreground cluster, allowing it to be... [+] imaged at high resolution and in multiple instruments, even without next-generation technology. This galaxy's light comes to us from 530 million years after the Big Bang, but the stars within it are at least 280 million years old. How we go from tiny galaxies like this to the massive ones we see a few hundred million years later is a mystery in galaxy evolution.
The standard expectation is that there's got to be some undiscovered type of galaxy in between these low-mass, early-type proto-galaxies and the heavy, massive, mature galaxies that we see. For those elusive galaxies to not appear in the same surveys that find both of the other types of galaxies means there must be something that's obscuring the light we're expecting to arrive.
For the most distant galaxies that are actively forming new stars at the greatest rates, we expect the light they'll emit will peak in ultraviolet wavelengths, just like they do for all massive star-forming regions where the light is dominated by stars significantly more massive than the Sun. After traveling through the expanding Universe, that light should redshift from ultraviolet through the visible part of the spectrum and all the way into the infrared. Yet our deepest infrared observations reveal only the early and late-type galaxies, not the intermediate type.
A young, star-forming region found within our own Milky Way. Note how the material around the stars... [+] gets ionized, and over time becomes transparent to all forms of light. Until that happens, however, the surrounding gas absorbs the radiation, emitting light of its own of a variety of wavelengths. In the early Universe, it takes hundreds of millions of years for the Universe to fully become transparent to light, and newly merged galaxies might require very long timescales to ionize all the obscuring gas-and-dust while the galaxy grows and forms stars.
Why could this be? The simplest explanation would be if something were blocking that light somehow. By the time the Universe is in the process of forming these very massive galaxies, it's already reionized, so we cannot blame the intergalactic medium for absorbing the light. But what might be a reasonable culprit is the gas and dust that belongs to the proto-galaxies which merge to form the late-type galaxies we eventually see.
Whenever you have a star-forming region, even if that region encompasses the entire galaxy, those stars are only able to form where you have neutral gas clouds collapsing. But neutral gas is exactly what we expect to block ultraviolet and visible light by absorbing it, and then re-radiating it at much longer wavelengths, dependent on the gas temperature. That light should be radiated in the infrared, and ought to be redshifted far into the microwave or even radio bands.
Light may be emitted at a particular wavelength, but the expansion of the Universe will stretch it... [+] as it travels. Light emitted in the ultraviolet will be shifted all the way into the infrared when considering a galaxy whose light arrives from 13.4 billion years ago; the Lyman-alpha transition at 121.5 nanometers becomes infrared radiation at the instrumental limits of Hubble. But warm gas, emitting in the infrared normally, will be redshifted all the way into the radio portion of the spectrum by the time it arrives at our eyes.
So instead of looking for redshifted starlight, you'd want to look for the signatures of warm dust that gets redshifted by the expansion of the Universe. You wouldn't use an optical/near-infrared observatory like Hubble, but rather a millimeter/submillimeter array of radio telescopes.
Well, the most powerful such array is ALMA, the Atacama Large Millimeter/submillimeter Array, which contains a collection of 66 radio telescopes designed for achieving high angular resolution and unprecedented sensitivity to detail in exactly that critical set of wavelengths. If you can find a faint, distant source of light that appears in these wavelengths and no others, you'll have discovered a candidate for exactly this type of "missing link" in galaxy formation. For the first time, a team of astronomers appears to have struck gold with exactly this discovery, by pure luck, in their observing field.
The Atacama Large Millimeter/submillimeter Array (ALMA) are some of the most powerful radio... [+] telescopes on Earth. These telescopes can measure long-wavelength signatures of atoms, molecules, and ions that are inaccessible to shorter-wavelength telescopes like Hubble, but can also measure details of protoplanetary systems and faint, early galaxies that may be obscured to more familiar wavelengths of light.
They made this discovery by looking at galaxies in the COSMOS field, a deep-field set of observations where many different observatories, including both Hubble and ALMA, have taken copious amounts of data. The team found two signals that corresponded to galaxies filled with warm dust and, therefore, rapid amounts of star formation. One of these corresponded to a run-of-the-mill late-type galaxy, but the other corresponded to no known galaxy at all.
When all the observations of this new galaxy candidate were combined, the astronomers studying it determined that it was:
Looking back through cosmic time in the Hubble Ultra Deep Field, ALMA traced the presence of carbon... [+] monoxide gas. This enabled astronomers to create a 3-D image of the star-forming potential of the cosmos. Gas-rich galaxies are shown in orange. You can clearly see, based on this image, how ALMA can spot features in galaxies that Hubble cannot, and how galaxies that may be entirely invisible to Hubble could be seen by ALMA.
The study's authors have expressed extreme excitement that this galaxy which appears in a survey area of just 8 square arcminutes (it would take 18 million such regions to cover the sky) might be a prototype for the "missing link" galaxies required to explain how the Universe grew up. According to study author Kate Whitaker,
"These otherwise hidden galaxies are truly intriguing; it makes you wonder if this is just the tip of the iceberg, with a whole new type of galaxy population just waiting to be discovered."
While other large galaxies, including star-forming galaxies, had been spotted before, none of them had large enough star-formation rates to possibly explain how the Universe's galaxies grew up so fast. But this galaxy changes all of that, according to first author Christina Williams, who noted,
"Our hidden monster galaxy has precisely the right ingredients to be that missing link, because they are probably a lot more common."
Optical telescopes like Hubble are extraordinary at revealing optical light, but the expansion of... [+] the Universe redshifts much of the light from distant galaxies out of Hubble's view. Infrared and longer wavelength observatories, like ALMA, can pick up the distant objects that are too redshifted for Hubble to see. In the future James Webb and ALMA, combined, might reveal details of these distant galaxies that we cannot even fathom today.
Up until now, scientists have been waiting for the James Webb Space Telescope humanity's next-generation, space-based infrared observatory to peer through the light-blocking dust and solve the mystery of how our Universe grew up. While Webb will certainly teach us more about these early, growing galaxies and reveal details that remain unseen, we've learned that these obscured monsters really are out there, and might be the missing link in galaxy growth and evolution.
Either we've gotten incredibly lucky in finding a very rare type of galaxy in such a small region of space, or this new find is an indicator that these behemoths really are everywhere. For now, this new discovery should leave us all hopeful that ALMA will continue to find more of these galaxies, and that when James Webb comes online, one more piece of the cosmic puzzle might slide perfectly into place.
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Posted: at 2:50 pm
Space, planets and galaxies have interested Simon Lewis for as long as he can remember. The Greendale resident talks to Devon Bolger about his passion for astronomy and work as an astrophotographer at the West Melton observatory
What was it that first attracted you to astronomy?
Even as a kid, Ive always been interested in science and technology. As a boy, I was always pulling things apart and trying to fix them, nothing was safe in my house. I started to grow this passion for space and our universe so this is kind of a natural progression for me because Ive taken that interest in science and technology and applied it to astrophotography which is what I specialise in.
What do you like about astrophotography?
Astrophotography really includes a large part of science and astronomy because youre trying to look at different type of objects using cameras and you have to try to understand the dynamics of what youre looking at, the size and scale of what youre looking at, and also the type of object youre looking at and even when it might be visible. You have to put some effort into it and thats the bit I like, theres a science behind it. You have to understand the night sky and the object your aiming for and then kind of frame it up from there to create something thats pleasing to the eye. Everybody that does astrophotography say its very much an art form in its own right. Theres result thats the correct one to aim for, you just give it the finish that is your interpretation of the subject and one which makes you happy.
Is there anything that you find particularly exciting when you photograph it?
I like to look at things that arent quite mainstream. There are definitely major celestial objects that are commonly photographed and if you picked up an astronomy magazine youd see pictures of them in there but I like to photograph more low key objects that are just as interesting. Theyre not always as photogenic perhaps but theyre very interesting in their own right. For example, theres an object near the Southern Cross called the Corona Australis that is whats called a dark nebula, which is actually dust that is blocking the light from stars so if you look at it you cant actually see any light through it because theyre being blocked by the dust. I quite like taking photographs of them and think theyre nice to look at because theyre not photographed very often.
What is your favourite constellation?
Not a constellation in particular, as our southern night sky is really fantastic there is so much to look at, so choosing one as a favourite is really hard. If you look directly to the south of us youve got Carina which is a fabulous constellation which has the Carina Nebula and whats called the Homunculus which is a bubble of gas round a huge star thats a 100 times bigger than ours. Its a really beautiful area to photograph. Orion is also a really amazing constellation to look at too. Its in our summer evening sky and it has a number of beautiful objects within it to image. If you look up and to the right from the stars on the belt youll see the Orion Nebula. Its so big and so bright you can see it without a telescope even by naked eye as a fuzzy patch, you can really see it very clearly in a pair of binoculars.
Do you think are aliens out there?
Well, Im always seeing strange and weird things out there at night. There are always satellites, space junk and meteors passing by us, but I think it would be a very lonely place and a very, very strange occurrence if human life was the only life in the universe. The problem I think is actually the distances involved and as an astronomer youre acutely aware of how far away some of these objects are. Even in our own galaxy, which is around 200,000 light-years from edge to edge, our radio signals have only managed to get around a hundred light-years distant from earth so far, so Im not surprised we havent run into anybody yet.
You are from England, how long have you lived in the district for?
I visited New Zealand in 2008 while I was living in Europe and I settled in West Melton after doing some travelling and decided I loved New Zealand and wanted to live and work here, so Ive been in Selwyn since I first arrived here. My met my wife here andwe moved out to a lifestyle block in Greendale in 2016, basically because its a beautiful place to live, its amazingly dark at night and we have some land for my wifes horses and room for my observatory.
Could you tell me about the work you do at the West Melton observatory and for the Canterbury Astronomical Society?
Im on the societys committee and I hold a couple of roles. Im the webmaster and handle the website as well ticketing for events and Facebook updates. Im also the membership officer. I also manage the content on the website and write the newsletter that we publish online monthly, we also publish a written magazine too. I play an active role in our public night programmes. Every Friday night we get about 80 to 90 people visiting the observatory. I might drive one of the telescopes or just wander around with binoculars talking to the kids and showing them whats in the sky and explain what theyre seeing. The kids love it, theyre always asking things like: Oh can we see a black hole? So you can really have a lot of fun just wandering around talking to them and explaining the night skies. We do that from the end of March until the end of September and during July we also do KidsFest where we are open every night if its clear, for 15 nights in a row.
Posted: at 2:49 pm
Lake Effect's Bonnie North speaking with astronomy contributor, Jean Creighton.
When people think of astronomers, several names come to mind: Isaac Newton, Galileo Galilei, or Carl Sagan all white men. But throughout history, women and other people of color have made huge contributions to our understanding of the cosmos.
Astronomy contributor Jean Creighton says that highlighting that diversity in the field is necessary for both kids and adults.
"It's so important to break those barriers, no matter who you are, no matter what you do, so that the stereotypes that people put in their heads are set aside," says Creighton.
She recalls that when she was a graduate student, most of her professors were male and "there were certain things that [she] felt they really couldn't answer."
Creighton notes that while diversity in astronomy has improved, there is still some ground to be gained.
Her advice? Look, ask and see. "If you can't see those people, they might be there anyway," notes Creighton. "And if they're not, yes, then it's your responsibility to try and become one."
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Posted: at 2:49 pm
VIPER will have four key instruments to detect water. The Neutron Spectrometer System will detect wet areas below the surface. Once an area looks promising, the rover will deploy its TRIDENT drill to dig into the soil. Two other instruments will analyze the soil samples.
On the mission, VIPER will collect different kinds of soil from different areas of the Moon, letting scientists map out exact locations where water is likely located.
With the Artemis missions beginning in the 2020s, water will be a key resource on the Moon. Deposits of ice water will be crucial for the longevity of a human settlement. Its not just drinking water thats in demand, either. Eventually, by mining the water ice, astronauts may be able to extract its hydrogen and oxygen and then use it to create rocket fuel. That could reduce the amount of fuel and supplies astronauts have to bring with them to the Moon, and even support future missions to Mars.
It can be used, and we need to use it, not just for life support but maybe even rocket fuel, said NASA administrator Jim Bridenstine.
Astronomers found water ice near the Moons south pole back in 2009, and scientists think its a promising spot to find more. And its not just NASA looking into the resources that might be hidden there. In September, India attempted to send their first lunar rover to the south pole to map the area and explore the region for water. However, the lander malfunctioned and crashed into the surface.
Engineers are already testing models of VIPER to see how it will move and function on the surface of the Moon. The final VIPER rover is being created by various NASA research centers, along with commercial partner, Honeybee Robotics, a Brooklyn-based company.
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Astronomers See Strontium in the Kilonova Wreckage, Proof that Neutron Star Collisions Manufacture Heavy Elements in the Universe – Universe Today
Posted: at 2:49 pm
Astronomers have spotted Strontium in the aftermath of a collision between two neutron stars. This is the first time a heavy element has ever been identified in a kilonova, the explosive aftermath of these types of collisions. The discovery plugs a hole in our understanding of how heavy elements form.
In 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the European VIRGO observatory detected gravitational waves coming from the merger of two neutron stars. The merger event was named GW170817, and it was about 130 million light years away in the galaxy NGC 4993.
The resulting kilonova is called AT2017gfo, and the European Southern Observatory (ESO) pointed several of their telescopes at it to observe it in different wavelengths. In particular, they pointed the Very Large Telescope (VLT) and its X-shooter instrument at the kilonova.
The X-shooter is a multi-wavelength spectrograph that observes in Ultraviolet B (UVB,) visible light, and Near Infrared (NIR.) Initially, X-shooter data suggested that there were heavier elements present in the kilonova. But until now, they couldnt identify individual elements.
This is the final stage of a decades-long chase to pin down the origin of the elements.
These new results are presented in a new study titled Identification of strontium in the merger of two neutron stars. The lead author is Darach Watson from the University of Copenhagen in Denmark. The paper was published in the journal Natureon 24 October 2019.
By reanalysing the 2017 data from the merger, we have now identified the signature of one heavy element in this fireball, strontium, proving that the collision of neutron stars creates this element in the Universe,said Watson in a press release.
The forging of the chemical elements is called nucleosynthesis. Scientists have known about it for decades. We know that elements form in supernovae, in the outer layers of aging stars, and in regular stars. But theres been a gap in our understanding when it comes to neutron capture, and how heavier elements are formed. According to Watson, this discovery fills that gap.
This is the final stage of a decades-long chase to pin down the origin of the elements,says Watson.We know now that the processes that created the elements happened mostly in ordinary stars, in supernova explosions, or in the outer layers of old stars. But, until now, we did not know the location of the final, undiscovered process, known as rapid neutron capture, that created the heavier elements in the periodic table.
There are two types of neutron capture: rapid and slow. Each type of neutron capture is responsible for the creation of about half of the elements heavier than iron. Rapid neutron capture allows an atomic nucleus to capture neutrons quicker than it can decay, creating heavy elements. The process was worked out decades ago, and circumstantial evidence pointed to kilonovae as the likely place for the rapid neutron capture process to take place. But it was never observed at an astrophysical site, until now.
Stars are hot enough to produce many of the elements. But only the most extreme hot environments can create heavier elements like Strontium. Only those environments, like this kilonova, have enough free neutrons around. In a kilonova, atoms are constantly bombarded by massive numbers of neutrons, allowing the rapid neutron capture process to create the heavier elements.
This is the first time that we can directly associate newly created material formed via neutron capture with a neutron star merger, confirming that neutron stars are made of neutrons and tying the long-debated rapid neutron capture process to such mergers,says Camilla Juul Hansen from the Max Planck Institute for Astronomy in Heidelberg, who played a major role in the study.
Even though the X-shooter data has been around for a couple years, astronomers werent certain that they were seeing strontium in the kilonova. They thought they were seeing it, but couldnt be sure right away. Our understanding of kilonovae and neutron star mergers is far from complete. There are complexities in the X-shooter spectra of the kilonova that had to be worked through, specifically when it comes to identifying the spectra of heavier elements.
We actually came up with the idea that we might be seeing strontium quite quickly after the event. However, showing that this was demonstrably the case turned out to be very difficult. This difficulty was due to our highly incomplete knowledge of the spectral appearance of the heavier elements in the periodic table,says University of Copenhagen researcher Jonatan Selsing, who was a key author on the paper.
Up until now, rapid neutron capture was much debated, but never observed. This work fills in one of the holes in our understanding of nucleosynthesis. But it goes further than that. It confirms the nature of neutron stars.
After the neutron was discovered by James Chadwick in 1932, scientists proposed the existence of the neutron star. In a 1934 paper, astronomers Fritz Zwicky and Walter Baade advanced the view that a super-nova represents the transition of an ordinary star into aneutron star, consisting mainly of neutrons. Such a star may possess a very small radius and an extremely high density.
Three decades later, neutron stars were linked and identified with pulsars. But there was no way to prove that neutron stars were made of neutrons, because astronomers couldnt obtain spectroscopic confirmation.
But this discovery, by identifying strontium, which could only have been synthesized under extreme neutron flux, proves that neutron stars are indeed made of neutrons. As the authors say in their paper, The identification here of an element that could only have been synthesized so quickly under an extreme neutron flux, provides the first direct spectroscopic evidence that neutron stars comprise neutron-rich matter.
This is important work. The discovery has plugged two holes in our understanding of the origin of elements. It confirms observationally what scientists knew theoretically. And thats always good.
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Posted: at 2:49 pm
Researchers have discovered streams of gas rotating in opposite directions around a distant, supermassive black hole. This finding offers new clues about how black holes grew so rapidly in the early universe.
This supermassive black hole lies at the heart of the spiral galaxy NGC 1068, or Messier 77, which is located approximately 47 million light-years from Earth. This black hole is hidden within a thick doughnut-shaped cloud of dust and gas.
Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, astronomers found that the black hole is actually surrounded by two counter-rotating disks of gas. The inner disk spans 2 to 4 light-years and rotates in the same direction as the galaxy, while the outer disk spans 4 to 22 light-years and spins in the opposite direction, according to a statement from ALMA.
"Thanks to the spectacular resolution of ALMA, we measured the movement of gas in the inner orbits around the black hole," lead author Violette Impellizzeri, an astronomer from the National Radio Astronomy Observatory (NRAO) who works at ALMA, said in the statement. "Surprisingly, we found two disks of gas rotating in opposite directions."
Earlier studies of NGC 1068 revealed that the black hole has a monster appetite. Gas from the region surrounding the black hole, also known as the accretion disk, falls into the black hole, is superheated and then is thrown back out into space at incredibly high speeds. This process makes it difficult for optical telescopes to see through the region around the black hole. Gas in counter-rotating disks is believed to be more unstable than gas in a single rotating accretion disk, according to the statement. Therefore, gas in counter-rotating disks is believed to fall into a black hole faster, which could help to explain how some supermassive black holes grow so quickly, Impellizzeri said.
Using ALMA's extremely capable zoom lens, astronomers were able to observe the molecular gas around the black hole in NGC 1068 in great detail. cPreviously, counter-rotation has only been observed in galaxies thousands of light-years away from the galactic center.
This ALMA image shows two disks of gas moving in opposite directions around a black hole in the galaxy NGC 1068. The colors represent the motion of the gas: blue is material moving toward us, red is moving away. The white triangles show the accelerated gas that is expelled from the inner disk forming a thick, obscuring cloud around the black hole.
(Image credit: ALMA (ESO/NAOJ/NRAO), V. Impellizzeri; NRAO/AUI/NSF, S. Dagnello.)
However, in this study, the counter-rotation around NGC 1068 was seen occurring on a much smaller scale, only tens of light-years from the central black hole, the researchers said.
"We did not expect to see this because gas falling into a black hole would normally spin around it in only one direction," Impellizzeri said. "Something must have disturbed the flow because it is impossible for a part of the disk to start rotating backward all on its own."
To explain the backward flow of gas observed in NGC 1068, the astronomers suggest that gas clouds may have fallen out of the host galaxy or, alternatively, a small, passing galaxy on a counter-rotating orbit may be captured in the accretion disk, according to the statement.
While the outer disk currently appears to be in a stable orbit around the inner disk, the researchers expect that it will eventually fall onto the inner disk.
"The rotating streams of gas will collide and become unstable, and the disks will likely collapse in a luminous event as the molecular gas falls into the black hole," co-author Jack Gallimore, a professor of physics and astronomy at Bucknell University in Lewisburg, Pennsylvania, said in the statement. "Unfortunately, we will not be there to witness the fireworks."
These findings were published Oct. 14 in the Astrophysical Journal Letters.
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Posted: at 2:49 pm
One of the major unanswered questions in astronomy is how our modern system of galaxies evolved into its present-day configuration in the first place. Now, researchers have found evidence of a massive galaxy that formed when the universe was far younger than it today, with a very different configuration than the galaxies we see in the modern era.
Astronomer Christina Williams, who authored the study, was working with the Atacama Large Millimeter Array (ALMA) when she observed an extremely faint galaxy in an area where no galaxy had previously been known to exist.
It was very mysterious because the light seemed not to be linked to any known galaxy at all, said Williams, a National Science Foundation postdoctoral fellow at the Steward Observatory. When I saw this galaxy was invisible at any other wavelength, I got really excited because it meant that it was probably really far away and hidden by clouds of dust.
So it was. And its discovery may help astronomers solve a longstanding problem with existing theories of galaxy formation. Because its obviously impossible for astronomers to create a bottle universe and then watch to see how galaxies form, we have to rely on computer models that generate results based on initial preconditions. If the model doesnt produce a universe that looks like the one we live in, you know the model is incorrect in some fashion.
Antenna galaxies NGC 4038 & 4039 mid-merger. Blue areas are areas of star formation. Image from Wikipedia
At present, theories suggest that star formation peaked about 3.5B years after the Big Bang, at a redshift value (expressed in terms of z) of 1.9. Redshift values do not scale linearly; they increase quickly as we approach the beginning of the universe. The cosmic microwave background radiation, which dates to ~389,000 years after the Big Bang, has a z value of 1089. The highest redshift galaxy yet detected is GN-z11, which is observed as it existed some 13.4B years ago, 400M years after the Big Bang, and has a redshift value of 11.09. Light from this newly detected galaxy (as yet unnamed) has traveled some 12.5B years to reach us and has an observed redshift value of z = 5.5 with a range of +/- 1.1.
One of the challenges for existing theories of early galaxy formation is that early galaxies appear to have gotten very big, very fast. There is a body of evidence suggesting that at redshift values of 3 or less, these rare-but-massive galaxies may account for half of the cosmic star formation rate density (CSFRD). Optical and near-infrared galaxies account for the other half of observed stars. Beyond z > 3, however, the situation is unclear. While a bare handful of these large, dust-obscured galaxies have been observed at greater redshift distances, the authors write that they trace only the very tip of the star formation rate (SFR) distribution at early times The total contribution of dust obscured star formation, and therefore the census of star formation in the early universe, is unknown.
The light the bit thats reaching us is probably caused by stars heating the gas clouds that sit between ourselves and the distant galaxy. The galaxy itself is completely obscured by this fog, though astronomers estimate its the approximate size of the Milky Way. Its far more active than our home, though. Rates of star formation may be up to 100x higher than the Milky Way is currently experiencing.
Star formation rates this high could explain how the early universe got so big, so fast, but we need to find a lot more galaxies like this to fully explain the implied rates of star formation in the early universe.
Our hidden monster galaxy has precisely the right ingredients to be that missing link, Williams explains, because they are probably a lot more common. The launch of the James Webb Space Telescope in 2021 should help shine more light on just how prevalent these large galaxies are.
Feature image by James Josephides, YouTube.
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Posted: at 2:49 pm
BD +20 307 should not have been so bright. For such an old binary star system, it should have appeared cool in our scopes. Instead, it looked hot.
The discovery of this, made over a decade ago, signalled to astronomers that something incredible had happened: BD +20 307, a solar system over 300 light-years from Earth, was the scene of a violent cosmic accident.
Exactly what had taken place was up for debate, but it was definitely something powerful enough to spew out a hot, cloudy aftermath of swirling dust and debris encircling the distant star system in a giant ring.
Early analysis suggested asteroids or planetesimals running into one another may have been the cause. Subsequent spectroscopic observations refined the hypothesis, and then in 2010, scientists concluded the excess of dust we were seeing was, in all likelihood, the result of actual worlds colliding.
That giant dust bowl surrounding BD +20 307? Countless tiny fragments left behind by two dead exoplanets that just couldn't avoid each other in all the vast emptiness of space.
Artist's impression of worlds colliding in BD +20 307. (NASA/SOFIA/Lynette Cook)
"A catastrophic collision of two rocky, planetary-scale bodies in the terrestrial zone is the most likely source for this warm dust," astronomers explained in a paper, acknowledging that evidence of such "cataclysmic impacts" was rare.
Rare they may be, but simulations suggest these run-ins do occur. For what it's worth, you might only be reading this because our own planet once had such an encounter. The Moon, perhaps, was another beneficiary.
Regardless of local history, the hypothetical explanation for what transpired far away in BD +20 307 just got supported by a new study led by astrophysicist Maggie Thompson from the University of California, Santa Cruz.
Most spectacularly of all, the new research indicates that in the past decade or so since the last observations, the hot, dusty legacy of this violent collision seems to have gotten either hotter or dustier.
New infrared readings taken with SOFIA (the Stratospheric Observatory for Infrared Astronomy) and its Faint Object Infrared Camera indicate the luminosity of the dust ring 300+ light-years away has actually brightened about 10 percent in recent years.
That's a significant burst in brightness, and it could mean there's more dust grains absorbing more heat from the starlight of BD +20 307's two stars or it could mean something else has happened to heat the same amount of dust up to a hotter temperature (such as hotter or closer stars), although such developments are extremely unlikely in a short timeframe of only years.
If the former eventuality is true and the surface area of the dusk disk visible to us here on Earth is somehow greater it might mean the chaotic, billowing fallout from the two worlds colliding is still unfolding.
It's an intriguing possibility, although the team notes we don't have enough evidence to know for sure just why this luminosity flux exists.
On all the data available, the researchers maintain the collision between planetary-scale bodies is "still the most likely origin for the system's extreme dust", but BD +20 307's strange brightening warrants plenty more investigation yet.
"The warm dust around BD +20 307 gives us a glimpse into what catastrophic impacts between rocky exoplanets might be like," Thompson says.
"We want to know how this system subsequently evolves after the extreme impact."
The findings are reported in The Astrophysical Journal.