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The Evolutionary Perspective
Daily Archives: October 29, 2020
Posted: October 29, 2020 at 6:24 pm
An artists impression of a very dusty galaxy in the early universe that already exhibits signs of a rotating disc. Reds represent gast while blues and browns represent dust as seen by the ALMA radio telescope array. Image: B. Saxton NRAO/AUI/NSF, ESO, NASA/STScI; NAOJ/Subaru
One might expect galaxies forming in the very early universe to be relatively free of dust and the heavy elements cooked up when successive generations of massive stars run out of nuclear fuel and explode in supernova blasts. That process takes time, and most infant galaxies could be expected to experience rapid growth spurts in the eventual transition between the primordial and mature stages in their development.
But in a survey of 118 young galaxies dating back to within 1 billion to 1.5 billion years after the Big Bang, astronomers were surprised to find many more mature galaxies than expected.
We didnt expect to see so much dust and heavy elements in these distant galaxies, said Andreas Faisst of the Infrared Processing and Analysis Center (IPAC) at the California Institute of Technology.
In fact, about 20 percent of the galaxies sampled in the survey are already very dusty and a significant fraction of the ultraviolet light from newborn stars is already hidden by this dust, said Daniel Schaerer of the University of Geneva.
The ALMA Large Program to Investigate C+ at Early Times, or ALPINE, survey is the largest multi-wavelength study of galaxies in the early universe, utilising optical observations by ground- and space-based telescopes, including Keck, Subaru, the Very Large Telescope and the Hubble and Spitzer space telescopes and radio observations using the Atacama Large Millimetre/submillimetre Array, or ALMA.
The ALMA observations allowed researchers to detect star formation hidden by thick dust that blocks optical and infrared wavelengths and to follow the motion of gas associated with star-forming regions, finding Hubble-dark galaxies that even the space telescope cannot see.
We want to see exactly where the dust is and how the gas moves around, said Paolo Cassata of the University of Padua in Italy. We also want to compare the dusty galaxies to others at the same distance and figure out if there might be something special about their environments.
Read the rest here:
Posted: at 6:24 pm
Water molecules have been detected in the Moons surface by NASAs flying Stratospheric Observatory for Infrared Astronomy (SOFIA). Researchers found traces of the life-sustaining substance in one of the largest lunar craters visible from Earth, the Clavius Crater. This ancient impact site receives a significant portion of sunlight compared to other areas of the Moon, which suggests that lunar water might not be limited to shadowy sites at the Moons poles.
Without a thick atmosphere, water on the sunlit lunar surface should just be lost to space, Casey Honniball, the studys lead author, said in a NASA press release. Yet somehow were seeing it. Something is generating the water, and something must be trapping it there.
The findings were published October 26 in Nature Astronomy.
Water, humanity, and the Moon
The key to how water could survive such a harsh lunar environment might be related to another harsh reality on the Moon: micrometeorites. These small pieces of space rock only a few hundredths of an inch or so wide rain down on the lunar surface, potentially forming beadlike glass structures upon impact.
Its these structures that the researchers think could trap and protect water molecules from sunlight. Alternatively, the researchers say, the water molecules could be caught between grains of lunar soil that shields them from sunlight. And depending on what exactly is protecting the newfound water from the Sun, scientists think astronauts may eventually be able to mine it.
However, its important to note that the amount of surface uncovered is still rather small. NASA compares the amount to 100 times less than is found in the Sahara Desert. So, researchers arent quite sure what these findings mean for supporting a sustainable human presence on the Moon.
The new find marks the first time SOFIA a modified Boeing 747 mounted with a 100-inch reflecting telescope has looked at the Moon. Follow-up flights by the aircraft will search for additional water signatures within sunlit portions of the Moon. The results will then be used to inform future NASA lunar missions, including NASAs Volatiles Investigating Polar Exploration Rover (VIPER).
Posted: at 6:24 pm
Finding Planet Nine may require looking at telescope images in a different light.
Astronomers are vetting a "shifting and stacking" technique that could aid the hunt for the putative world, which some researchers think lurks undiscovered in the far outer system, way beyond Pluto's orbit.
The strategy involves shifting space-telescope images along sets of possible orbital paths, then stacking the photos together to combine their light. The technique has already been used to discover some moons in our solar system, and it could potentially spot Planet Nine also known as Planet X, Giant Planet Five or Planet Next and other extremely farflung objects, researchers said.
Related: The evidence for 'Planet Nine' in our solar system (gallery)
"You really cant see them without using this kind of method," Malena Rice, an astronomy Ph.D. student at Yale University in Connecticut, said in a statement. "If Planet Nine is out there, its going to be incredibly dim."
Rice is lead author of a new study that put the method into action. She and co-author Greg Laughlin, an astronomy professor at Yale, shifted and stacked images captured by NASA's Transiting Exoplanet Survey Satellite (TESS), which hunts for alien worlds from Earth orbit.
In a test, the researchers found the faint signals of three known trans-Neptunian objects (TNOs) small bodies that circle the sun beyond Neptune's orbit in shifted and stacked TESS images. The scientists then conducted a blind search of two distant patches of sky, turning up 17 new TNO candidates.
"If even one of these candidate objects is real, it would help us to understand the dynamics of the outer solar system and the likely properties of Planet Nine," Rice said. "Its compelling new information."
The researchers are currently working to confirm the 17 candidate TNOs, using imagery captured by ground-based telescopes.
TNOs are bread crumbs that could lead to the way to Planet Nine. Researchers have inferred the hypothetical world's existence from the odd orbits of some TNOs, which they say are clustered in a way that strongly suggests sculpting by a big, farflung "perturber." The data indicate a planet five to 10 times more massive than Earth, orbiting the sun hundreds of times farther away than our world does.
Not everyone is on board with this interpretation, however. Some scientists think the TNOs' odd clustering arises from the combined gravitational influence of their many minuscule neighbors, not a single big object.
The new study has been accepted by The Planetary Science Journal. Rice presented the results today (Oct. 27) at the annual meeting of the American Astronomical Societys Division for Planetary Sciences, which is being held virtually this year.
Editor's note: This story was updated at 4:20 p.m. EDT to clarify that Rice, not Laughlin, is lead author of the new study.
Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
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Posted: at 6:24 pm
As you drive down the road leading to Jodrell Bank Observatory, a sign asks visitors to turn off their mobile phones, stating that the Lovell telescope is so powerful it could detect a phone signal on Mars.
Radio telescopes are designed to be incredibly sensitive. To quote the legendary astronomer Carl Sagan, The total amount of energy from outside the solar system ever received by all the radio telescopes on the planet Earth is less than the energy of a single snowflake striking the ground.
The total energy now is probably a few snowflakes worth, but nevertheless it is still true that astronomical radio signals are typically magnitudes smaller than artificial ones. If Jodrell Bank could pick up interference from a phone signal on Mars, how would it fare with an entire 4G network on the Moon?
That is the issue that is worrying astronomers like me, now that Nokia of America has been awarded US$14.1m (10.8m) for the development of the first ever cellular network on the Moon. The LTE/4G network will aim to facilitate long term lunar habitability, providing communications for key aspects such as lunar rovers and navigation.
Radio frequency interference (RFI) is the long-term nemesis of radio astronomers. Jodrell Bank the earliest radio astronomy observatory in the world still in existence was created because of RFI. Sir Bernard Lovell, one of the pioneers of radio astronomy, found his work at Manchester hampered by RFI from passing trams in the city, and he persuaded the universitys botany department to let him move to their fields in Cheshire for two weeks (he never left).
Since then, radio telescopes have been built more and more remotely in an attempt to avoid RFI, with the upcoming Square Kilometre Array (SKA) telescope being built across remote areas of South Africa and Australia. This helps to cut out many common sources for RFI, including mobile phones and microwave ovens. However, ground-based radio telescopes cannot completely avoid space-based sources of RFI such as satellites or a future lunar telecommunications network.
RFI can be mitigated at the source with appropriate shielding and precision in the emission of signals. Astronomers are constantly developing strategies to cut RFI from their data. But this increasingly relies on the goodwill of private companies to ensure that at least some radio frequencies are protected for astronomy.
A long-term dream of many radio astronomers would be to have a radio telescope on the far side of the Moon. In addition to being shielded from Earth-based signals, it would also be able to observe at the lowest radio frequencies, which on Earth are particularly affected by a part of the atmosphere called the ionosphere. Observing at low radio frequencies can help answer fundamental questions about the universe, such as what it was like in the first few moments after the big bang.
The science case has already been recognised with the Netherlands-China Low Frequency Explorer, a telescope repurposed from the Queqiao relay satellite sent to the Moon in the Change 4 mission . Nasa has also funded a project on the feasibility of turning a lunar crater into a radio telescope with a lining of wire mesh.
Read more: China lands on the far side of moon here is the science behind the mission
Despite its interest in these radio projects, Nasa also has its eye commercial partnerships. Nokia is just one of 14 American companies Nasa is working with in a new set of partnerships, worth more than US$370m, for the development of its Artemis programme, which aims to return astronauts to the Moon by 2024.
The involvement of private companies in space technology is not new. And the rights and wrongs have long been debated. Drawing possibly the most attention has been SpaceXs Starlink satellites, which caused a stir among astronomers after their first major launch in 2019.
Read more: Space junk: Astronomers worry as private companies push ahead with satellite launches
Images quickly began to emerge with trails of Starlink satellites cutting across them often obscuring or outshining the original astronomical targets.
Astronomers have had to deal with satellites for a long time, but Starlinks numbers and brightness are unprecedented and and their orbits are difficult to predict. These concerns apply to anyone doing ground-based astronomy, whether they use an optical or a radio telescope.
A recent analysis of satellite impact on radio astronomy was released by the SKA Organisation, which is developing the next generation of radio telescope technology for the Square Kilometre Array. It calculated that the SKA telescopes would be 70% less sensitive in the radio band that Starlink uses for communications, assuming an eventual number of 6,400 Starlink satellites.
As space becomes more and more commercialised, the sky is filling with an increasing volume of technology. That is why it has never been more important to have regulations protecting astronomy. To help ensure that as we take further steps into space, well still be able to gaze at it from our home on Earth.
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Posted: at 6:24 pm
After more than six months of COVID-related closures, observational astronomy is largely getting back to work.
Many of the worlds biggest telescopes have reopened their domes in recent weeks, returning their gazes to the heavens for the first time since the pandemic forced a global shutdown of observational astronomy in March. Other major telescopes expect to reopen soon.
This wave of reopenings was buoyed by declining COVID-19 cases in Chile, especially in the Atacama Desert, a region home to many world-class observatories. U.S. officials who manage telescopes in Hawaii and Arizona say theyre also beginning to resume operations, largely thanks to significant changes in their workflows.
If major observatories continue to come back online and remain open it will end an unprecedented dark era in astronomy. After all, even during World War II, Americas observatories kept a close eye on the skies.
They have to live on campus part-time. Even the astronomers using the instruments typically travel to the observatories during their awarded observing nights.This reality forced observatories to shut down in the early days of the pandemic. There was no way to abide by social distancing rules and effectively run the telescopes. In interviews back in March, observatory directors said they expected telescopes to be offline for at least three to six months. And thats largely how the pandemic played out for them.
Luckily for the field, those survey telescopes didnt pick up any once-in-a-lifetime objects that would leave astronomers agonizing over what might have been.
Although not a light-gathering observatory,LIGO, the Laser Interferometer Gravitational-Wave Observatory, was forced to shut down its observing run a month early due to COVID-19. LIGO was planned to be offline for upgrades until 2022, but the pandemic is causing delays that could extend the process even longer. Processing the data from the last observing run is also taking longer than expected.
Posted: at 6:24 pm
This article was originally published atThe Conversation.The publication contributed the article to Space.com'sExpert Voices: Op-Ed & Insights.
Chris Impey, University Distinguished Professor of Astronomy, University of Arizona
This is a challenging time for families. Schools across the U.S. are struggling to provide a meaningful online experience. The coronavirus pandemic has cut off or restricted many entertainment options. As anastronomer, I believe a great way for families to fill the void and have a meaningful science experience in the time of COVID-19 is to turn their attention to the stars they can see right outside their homes.
The night sky is, and always has been, safe and free.
Here are five ways you can get started.
You can see a lot with just your eyes. But the night sky is a strange landscape to most people. Just as you would when traveling somewhere unfamiliar, youll need a map.Sky and Telescope an astronomy news publication has a guide to get started, withprintable sky mapsfor any month. The objects of the night sky migrate through a complete cycle over the course of a year.
As the Earth moves around the sun, different stars and constellations come into view, so you can enjoy new sights all through the year. You may find it more convenient to have a planisphere, or sky wheel, a rotating plastic disk thatshows the night sky for any date and time. They can be bought for US$10-$20 online.
Spotting planets is trickier since they move among the stars, but there are interactive maps online that show them in thenight sky for any time at any location. Your view of the night sky depends on your latitude, so it varies with your specific location. Even easier, there aresmartphone appsthat take all the work and maybe also the fun out of navigating the night sky.
Hold your phone up and the apps identify stars and overlay the constellation shapes. Some respond to voice commands and add detailed information on celestial objects or show theInternational Space Stationas it whizzes overhead.
You probably have a pair of binoculars somewhere in your house. If you dont or you want an upgrade, new binoculars cost anywhere from $35 to over $500, and the lower end of the range is justfine for stargazing.
Perhaps you use them at concerts or for bird-watching. Well, theyre alsoperfect for stargazing. There are two numbers on binoculars. They represent the magnification and the lens diameter, so 7 x 50 will magnify an image by a factor of 7 using 50-millimeter lenses. At a dark location, your naked eye will see about 3000 stars. With binoculars this number goes up to 100,000.
Themoon is spectacular through binoculars. Its fun for kids to track a cycle of the moon phases over a month, and then do anactivity that shows why the moon has phases.
If you want to make a bigger commitment to exploring the night sky, consider getting a small telescope. Peering through a telescope opens up a world of star clusters, galaxies and nebulae. You can see Saturns rings and the moons of Jupiter.
Its a good idea toread a guidebefore you take the plunge. Small telescopes range from a hundred to several thousand dollars, but you can get agood starter onefor as little as $200. These basic telescopes usually have a viewfinder attached to help locate objects, but youll need sky maps to get the most out of them.
If you can shell out at least $400, you can acquire what are called GoTo telescopes that have motors and are computer controlled, where thetelescope does the work of finding the deep sky objects. You just have to type the name in or choose from a list. Now youll be ready to learntricks of the trade, like using a red LED flashlight to preserve your night vision, and looking slightly to the side, which lets you see deeper because the cells near the edge of your retina are more sensitive to low light levels.
The internet is a great resource for backyard astronomy. You might want to start with aCrash Coursein naked-eye astronomy. In addition to reviews of apps and binoculars and telescopes, there aretutorials on how to use your new telescope.
Youll also want to check out Sky and Telescopes weeklySky at a Glance.BBCsSky at Night magazinehas alonger monthly summaryof what you can observe.
And if you just want to be inspired by thevisual splendorof a dark night sky, there are a number oftime-lapse videosyou can enjoy.
Hopefully youre excited about backyard astronomy, but what you can actually see will depend on where you live.
For tens of thousands of years, the night sky was a familiar friend to our ancestors, and they used it to navigate, tell time and project their myths into the stars and constellations. But the glories of the night sky have been steadily eroded by industrial activity and artificial lights.
[The Conversations science, health and technology editors pick their favorite stories.Weekly on Wednesdays.]
You can see recent measures of night sky brightness in azoomable mapof the U.S., where its clearly harder to find a dark sky in the eastern half of the country.
To measure how sky brightness affects what you can see, amateur astronomers use something called theBortle scale, where 9 is an inner city and 1 is a pristine wilderness.Light pollutionis the effect of artificial lighting on the night sky, and you can also see how it affects the familiarBig Dipper and Orionconstellations.
National parksare great places to enjoy the sky because they try to protect it from artificial lights, and in normal times many national parks offerastronomy programs. Many are also beginning toresume those programswith COVID-19 restrictions in place.
If you want to contribute to the effort to raise awareness of light pollution by monitoring the sky brightness where you live, the U.S. national observatories run a project called Globe at Night.
Anyone can collect data and help a research project by doingcitizen science, which is when non-scientists gather data and contribute to a collective research effort. You can become a citizen scientist and submit your own observations from a computer or smartphone.
This article is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.
Follow all of the Expert Voices issues and debates and become part of the discussion on Facebook and Twitter. The views expressed are those of the author and do not necessarily reflect the views of the publisher.
Posted: at 6:24 pm
The scientists work offers new insights into recent theories that indicate that Venus could have had an atmosphere similar to that of Earth billions of years ago, before it acquired its current atmosphere.
Maria Antonia Sendas & Alexandra Galloway 10:31 pm, Oct 26, 2020
Anasthasia Shilov, Illustrations Editor
Yale astronomers Samuel Cabot GRD 24 and professor Gregory Laughlin published a study last month in the Planetary Science Journal which investigates a theory suggesting that pieces of Venus may have crashed into the moon.
Cabot and Laughlins research offers new insights into recent theories that indicate that Venus could have had an atmosphere similar to that of Earth billions of years ago, before it acquired its current atmosphere, which is dense with carbon dioxide and contains clouds of sulfuric acid. The researchers found that asteroids and comets that crashed into Venus may have dislodged as many as 10 billion rocks, sending them into orbit and causing them to intersect with the Earth and the moon.
If Venus once had a thin atmosphere, said Cabot, a graduate student in the Yale Department of Astronomy and the lead author of the study, then wed expect to find a certain amount of Venus fragments on the moon.
The investigation began as Cabots one-year project, in which first-year graduate students in the astronomy department are paired with an advisor, conduct research on an area of interest to them and explore the diversity of research opportunities in astronomy. Students have access to a wide range of resources to support their research, including supercomputers and observational tools such as telescopes.
Laughlin, who is a professor of astronomy and physics at Yale, acted as Cabots advisor, and together they were inspired by the recent resurgence of interest in space exploration and, in particular, missions to the moon, Cabot told the News. As an example, he mentioned NASAs Artemis Program the twin sister of the Apollo space missions.
With the Artemis program, NASA will land the first woman and next man on the Moon by 2024, using innovative technologies to explore more of the lunar surface than ever before, stated the projects website.
The project plans to return humans to the moon but also aspires to eventually send astronauts to Mars. It stands to open up new possibilities for research in space.
With upcoming missions to the moon through Artemis, Cabot and Laughlin wanted to investigate what could be learned about Venus by looking at lunar regolith, the moons soil. However, they faced some initial obstacles in answering this question.
The biggest challenge was where to start, Cabot said.
The question of whether there could be pieces of Venus on the moon is deceptively simple answering it is far more complicated than it seems. During the course of their research, Cabot and Laughlin had to constantly ask themselves if they were using the proper physics, processes and tools to answer the question and double-check whether their findings were consistent with what was physically possible.
They found that it is physically feasible for pieces of Venus to have ended up on the moon, assuming that Venus atmosphere was once similar to that of Earth. Cabot explained. However, because his and Laughlins work was theoretical, he said, their results will need to be confirmed by the presence of fragments from Venus on the moon. According to him, it is possible that none will be found. Either way, the discovery of rock or lack thereof could provide information about the thickness of Venus atmosphere and whether it ever contained liquid water.
Earth is the only planet in the solar system that currently has liquid water. Venus is often referred to as the Earths sister planet due to their similar masses, volumes and densities. Their commonalities may even extend to their atmospheres, as Venus may have had one like Earths as recently as 700 million years ago, according to a Yale News article.
Cabot and Laughlins research could shed light on Venus mysterious history. Knowing more about the planets past may help researchers better understand what happened to Venus and why its physical characteristics diverged significantly from the Earths since its formation.
Were quite confident that Venus has a low mass atmosphere in its history [and] that there were plenty of asteroids and comets that blasted pieces of Venus off, Laughlin told the News. But understanding exactly what happened to them is one of our biggest challenges.
Their research also suggests new directions for further exploration. In the future, they hope to obtain physical moon samples from Apollo missions to test their theory.
Cabot emphasized that while these questions seem simple, there are unique challenges to answering them. Although it is possible to compare rock samples with those gathered by Mars rovers to tell whether something originated from Mars, it is much more difficult to do the same for Venus. Unlike Mars, Venus current atmosphere could be significantly different from its past atmosphere.
The next steps are finding the correct fingerprint for Venus and identifying what it takes to identify meteorites from Venus, he said.
Future research, Cabot explained, must innovate methods for determining a samples origins, either through chemical analysis or by studying the isotopic composition of samples. Different amounts of certain isotopes could reveal important insights about when rocks arrived on the moon and where they may have come from.
A day on Venus lasts longer than a year on Earth.
Alexandra Galloway | firstname.lastname@example.org
Maria Antonia Sendas | email@example.com
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Astronomers Find the Hollowed-Out Shell of a Dwarf Galaxy that Collided With the Milky Way Billions of Years Ago – Universe Today
Posted: at 6:24 pm
In 2005 astronomers found a dense grouping of stars in the Virgo constellation. It looked like a star cluster, except further surveys showed that some of the stars are moving towards us, and some are moving away. That finding was unexpected and suggested the Stream was no simple star cluster.
A 2019 study showed that the grouping of stars is no star cluster at all; instead, its the hollowed-out shell of a dwarf spheroidal galaxy that merged with the Milky Way. Its called the Virgo Overdensity (VOD) or the Virgo Stellar Stream.
A new study involving some of the same researchers shows how and when the merger occurred and identifies other shells from the same merger.
The new papers title is The Milky Ways Shell Structure Reveals the Time of a Radial Collision. The first author is Thomas Donlon II, a Rensselaer grad student, who was also the first author of the 2019 study. The paper is published in The Astrophysical Journal.
In their paper, the authors write In this work, we identify shell substructure in the Milky Way for the first time, and we argue that these shells are indeed associated with the VRM and therefore a radial merger event.
There are different types of mergers, and according to the 2019 paper, the merger that created the VOD was whats known as a radial merger. These are violent merger types that a press release describes as a stellar version of a T-bone crash.
When we put it together, it was an aha moment, said Heidi Jo Newberg, Rensselaer professor of physics, applied physics, and astronomy, and lead author of The Astrophysical Journal2019 paper detailing the discovery. This group of stars had a whole bunch of different velocities, which was very strange. But now that we see their motion as a whole, we understand why the velocities are different, and why they are moving the way that they are.
The new paper builds on that work and reveals even more detail. As the dwarf galaxy collided with the Milky Way, it left behind curved planes of stars that kind of bounce through the galactic center. Theyve called the event the Virgo Radial Merger (VRM).
Each time the dwarf galaxy collides with the galactic center, it barrels out the other side, only to be drawn back toward the center. Each time it reaches the furthest point, it leaves behind some of its stars, forming the shells. The team created simulations using the observational data and calculated how many times the dwarf galaxy has bounced back and forth and when it first merged with the Milky Way.
The team of researchers used data from multiple sources. Using data from the Sloan Digital Sky Survey, the ESAs Gaia mission, and the LAMOST telescope in China, they found two shell structures in the VOD and two more in the Hercules Aquila Cloud region. Their computer modeling showed that the merger began when the dwarf galaxy first passed through the Milky Ways center 2.7 billion years ago.
Galaxy mergers are not rare. Huge galaxies like the Milky Way grew large by merging with much smaller galaxies. Currently, the Milky Way is in the middle of two mergers. Its in the process of merging with the Sagittarius Dwarf Spheroidal Galaxy and with both the Small and Large Magellanic Clouds.
All these mergers have left their mark on the Milky Way. Our galaxys halo is a region of stars in a spherical shape surrounding the Milky Ways spiral arms. The majority of those stars are not native to the galaxy, but instead are immigrants from other galaxies that merged with the Milky Way.
Over time, the tidal forces of the galaxy shape those immigrants into long streams of stars. Those streams move in concert with each other through the halo. Astronomers call these tidal mergers, and theyre the focus of much research.
But this merger was different. Radial mergers like this one are much more violent, and the dwarf galaxy can whipsaw back and forth multiple times, leaving these shell shapes.
In a press release, first author Thomas Donlon II explained that the team was not actively looking for evidence of one of these radial mergers.
There are other galaxies, typically more spherical galaxies, that have a very pronounced shell structure, so you know that these things happen, but weve looked in the Milky Way and hadnt seen really obvious gigantic shells, said Donlon, who was also the lead author on the 2019 paper that first proposed the Virgo Radial Merger.
As the team worked on their study, the whip-saw motion of the stars in the VOD became clearer in their modeling. Thats when they had to consider a radial merger as the cause. And then we realized that its the same type of merger that causes these big shells, said Donlon II. It just looks different because, for one thing, were inside the Milky Way, so we have a different perspective, and also this is a disk galaxy, and we dont have as many examples of shell structures in disk galaxies.
This finding is also shedding new light on some other aspects of the Milky Ways morphology, including the Gaia Sausage. The Gaia Sausage is the remains of another dwarf galaxy that merged with the Milky Way. That merger happened between 8 and 10 billion years ago and added eight globular clusters and about 50 billion solar masses of stars, gas, and dark matter to the Milky Way. It has the characteristic shape of a sausage due to the orbits of the stars.
Prior to this work, astronomers tended to think that the Virgo Radial Merger and the Gaia Sausage were outcomes of the same event. But now theres a much younger estimate for the VRM, and the two are understood to be separate events. If theyre not separate events, then the time estimate for the Gaia Sausage has to be younger, which means that the Sausage cant be responsible for causing the Milky Ways disk to be so thick, which is one of the results attributed to the more ancient estimate for the Gaia Sausage event.
This work is potentially shedding some new light on other parts of the Milky Way, too. The Gaia Snail is a spiral-shaped group of stars near the Sun that may be connected with the VRM, and another event called the Splash might be, too. The Splash is a substructure in the Milky Ways disk near the Sun. It has a large population of metal-rich stars moving through highly radial orbits in the inner halo. There are many questions around the origin of the Splash, but this study shows that the VRM could have caused it, and other more ancient mergers arent needed to explain it.
There are lots of potential tie-ins to this finding, Newberg said. The Virgo Radial Merger opens the door to a greater understanding of other phenomena that we see and dont fully understand, and that could very well have been affected by something having fallen right through the middle of the galaxy less than 3 billion years ago.
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Astronomers are ready and waiting to detect the neutrino blast from a nearby supernova explosion like Betelgeuse – Universe Today
Posted: at 6:24 pm
When giant stars die in impressive supernova blasts, about 99% of the energy released goes into producing a flood of neutrinos. These tiny, ghostly particles slip through tons of matter like its not even there. But a new generation of detectors will be able to catch them, telling us of the inner machinations of the deaths of stars.
In 1987 the astronomy world witnessed the closest supernova explosion seen in centuries, a blast set off from within the Large Magellanic Cloud, a mere 168,000 lightyears away. One of biggest surprises and delights of that explosion was the clear detection of neutrinos from the event.
Neutrinos are subatomic particles that barely even acknowledge the rest of the particles in the universe. They are produced in all kinds of nuclear reactions (everywhere from nuclear power plants to giant stars exploding), and trillions of them are flying through your body right now. But since they hardly ever interact with normal matter, you dont even notice them.
The detection of neutrinos in 1987 was a big deal because it taught us that supernovae can create a tremendous amount of neutrinos. Indeed, less than 1% of the total energy of a supernova explosion goes into light. And given the fact that a single supernova can outshine entire galaxies, its amazing to contemplate the sheer number of neutrinos produced with the other 99% of the available energy.
Unfortunately, a combination of extreme distance and the ninja-like stealthiness of neutrinos means that our Earthbound detectors caught only a handful of neutrinos from the 1987 event.
But this time it will be different.
A collaboration of scientists from around the world is currently constructing DUNE, the Deep Underground Neutrino Experiment. This experiment will mainly detect neutrinos produced at Fermilab using a giant tank of liquid argon at the Sanford Underground Research Facility in South Dakota. But the facility is also capable of detecting neutrinos from cosmic sources, and Betelgeuse is a prime candidate.
Betelgeuse is a red giant star in the constellation Orion, about 548 lightyears away from us. This star is near the end of its life, and is due to go supernova any day now. Of course, in astronomy terms any day now means within the next 100,000 years or so.
But it could also meanliterally any day now. If Betelgeuse goes supernova, it will be visible during the daytime and produce enough light to cast shadows at night. And it will also generate an enormous flood of neutrinos, giving astronomers at DUNE an unprecedented front-seat view to the heart of a giant star in the last moments of its life.
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A team of researchers has discovered a complex network of filamentary structures in the Milky Way. The structures are made of atomic hydrogen gas. And we all know that stars are made mostly of hydrogen gas.
Not only is all that hydrogen potential future star-stuff, the team found that its filamentary structure is also a historical imprint of some of the goings-on in the Milky Way.
The paper announcing this finding is titled The history of dynamics and stellar feedback revealed by the HIfilamentary structure in the disk of the Milky Way. The lead researcher is Juan Diego Soler from the Max Planck Institute of Astronomy (MPIA). The paper is published in the journal Astronomy and Astrophysics.
The authors introduce their paper by saying The diffuse neutral atomic hydrogen (HI) is the matrix within which star-forming clouds reside and the medium that takes in the energy injected by stellar winds, ionizing radiation, and supernovae. The observation of its distribution and dynamics provides a crucial piece of evidence to understand the cycle of energy and matter in the interstellar medium (ISM).
The study is based on an MPIA project called THOR (The HI/OH/Recombination line). THOR is a survey based on the famous H1 line or hydrogen line. The H1 line is an often used part of astronomical observations. Its based on the spectral line produced by neutral hydrogen atoms when their energy state changes. The H1 line is at a 21 cm wavelength, which is easily observed by radio telescopes and can penetrate interstellar dust that blocks visible light.
We are reconstructing the Milky Way history using the clouds of atomic hydrogen gas.
Because of the properties of the H1 line, and the Very Large Array (VLA) radio interferometer that gathered the data for THOR, the survey provides maps of gas distribution in the inner Milky Way that have the highest spatial resolution to date, according to a press release.
The latest addition to the THOR data set is our data release 2 that includes a census of the neutral atomic hydrogen at an angular resolution of 40 arcseconds, Henrik Beuther explains, who leads the THOR project at MPIA, explained in the release.
Co-author Yuan Wang was partly responsible for processing the THOR data for this study. We used the famous spectral line of hydrogen located at a wavelength of 21 cm, Yuan Wang explains. These data also provide the gas velocity in the direction of observation. Combined with a model of how the gas in the Milky Way disk rotates around its center, we even can infer distances, Wang added. Thanks to the high resolution in the THOR observations, completely new studies were possible.
Lead author Soler was also responsible for processing the THOR data. He applied an algorithm to the data to get a better look at hydrogen distribution. The algorithm was the same one used in satellite image analysis and character recognition. That algorithm revealed the detailed filamentary nature of hydrogen.
Most of the hydrogen filaments are parallel to the Milky Ways disk. One of the hydrogen lanes, which Soler named Magdalena after the longest river in his home country of Colombia, is 3,000 light-years long. At that length, it might be one of the largest structures in the entire galaxy.
Maggie [Magdalena] could be the largest known coherent object in the Milky Way. In recent years, astronomers have studied many molecular filaments, but Maggie seems to be purely atomic. Because of its fortunate position in the Milky Way, we are lucky to have been able to spot it, said Jonas Syed, a Ph.D. student at MPIA, who is also part of the THOR team.
But Maggie didnt garner the most attention. Instead, the researchers were interested in a group of vertical hydrogen filaments.
The thing about the Milky Way is that its rotating. And that rotation should stretch out the hydrogen filaments parallel to and on the same plane as the Milky Way. So why is one group of filaments vertical?
Like in the spinning pizza dough, we expected that most of the filaments would be parallel to the plane and stretched by the rotation. But when we found many vertical filaments around regions known for their high star formation activity, we knew we were onto something. Some process must have been blowing material off the Galactic plane, Soler explained.
That process was likely massive stars that explode as supernovae at the end of their lives.
Those massive stars have powerful stellar winds with the power to shape their surroundings, including hydrogen, which is easily pushed around. The stars ionizing radiation helps the process along. This brings it around to the H1 line again.
The H1 line has been used for all sorts of observations, including searching for and identifying the gas shells around stars that have gone supernova. The powerful shock waves from supernova slam into hydrogen gas, causing it to build up into clumps, and sometimes triggering new star formation. But that isnt quite what happened with the vertical filaments that THOR found.
Most of the vertical filaments of atomic hydrogen are in regions that have a known, long history of star formation. Several generations of stars and supernovae have shaped the region, and the team of researchers linked the vertical filaments to events that came long before the shells carved out by supernovae.
Most likely, we are looking at the remnant of many older shells that popped when they reached the edge of the Galactic disk, accumulated over millions of years, and remain coherent thanks to the magnetic fields, Soler explains.
This study gives us a new look at some of the dynamic processes going on in galaxies. It links observations with the physical processes that cause gas to accumulate, and then to form new stars. Our results indicate that a systematic characterization of the emission morphology toward the Galactic plane provides an unexplored link between the observations and the dynamical behavior of the interstellar medium, from the effect of large-scale Galactic dynamics to the Galactic fountains driven by SNe, the authors write in their paper.
Galaxies are complex dynamical systems, and new clues are hard to obtain. Archaeologists reconstitute civilizations from the ruins of cities. Palaeontologists piece together ancient ecosystems from dinosaur bones. We are reconstructing the Milky Way history using the clouds of atomic hydrogen gas, Soler concludes.
The team thinks that their methodology can be applied to other regions of the galaxy to reveal the nature of neutral atomic hydrogen structures. Will there be more Magdalenas?
The statistical nature of our study unveils general trends in the structure of the atomic gas in the Galaxy and motivates additional high-resolution observations of the HIemission in other regions of the Galaxy, the authors write in their conclusion. Our results demonstrate that measuring the orientation of filamentary structures in the Galactic plane is a promising tool to reveal the imprint of the Galactic dynamics, stellar feedback, and magnetic fields in the observed structure of the Milky Way and other galaxies.
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