Alien4  Posted at 2024-01-10 21:44:59(15Wks ago) Report Permalink URL | ||
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| Nube, the almost invisible galaxy that challenges the dark matter model by Instituto de Astrofísica de Canarias  The Nube galaxy. The figure is a composition of a color image and a black and white image, to pick out the background. Credit: GTC/Mireia Montes Nube is an almost invisible dwarf galaxy discovered by an international research team led by the Instituto de Astrofísica de Canarias (IAC) in collaboration with the University of La Laguna (ULL) and other institutions. The name was suggested by the 5-year-old daughter of one of the researchers in the group and is due to the diffuse appearance of the object. Its surface brightness is to faint that it had passed unnoticed in the various previous surveys of this part of the sky due to the object's diffuse appearance as if it were some kind of ghost. This is because its stars are so spread out in such a large volume that "Nube" (Spanish for "Cloud") was almost undetectable. This newly discovered galaxy has a set of specific properties which distinguish it from previously known objects. The research team estimate that Nube is a dwarf galaxy 10 times fainter than others of its type, but also 10 times more extended than other objects with a comparable number of stars. To show what this means to anyone who knows a little astronomy, this galaxy is one-third of the size of the Milky Way but has a mass similar to that of the Small Magellanic Cloud. "With our present knowledge, we do not understand how a galaxy with such extreme characteristics can exist," explains Mireia Montes, the first author of the article and a researcher at the IAC and the ULL. For some years, Ignacio Trujillo, the second author of the article, has been analyzing, based on the Sloan Digital Sky Survey (SDSS) images, a specific strip of sky in the framework of the project Legado del IAC Stripe 82. In one of the data revisions, they noticed a faint patch that looked sufficiently interesting to set up a research project. The next step was to use ultra-deep multicolor images from the Gran Telescopio Canarias (GTC) to confirm that this patch in the survey was not some type of error but an extremely diffuse object. Due to its faintness, it is hard to determine the exact distance of the Nube. Using an observation obtained with the Green Bank Telescope (GBT) in the United States, the authors estimated the distance of Nube to be 300 million light years, although upcoming observations with the Very Large Array (VLA) radiotelescope and the optical William Herschel Telescope (WHT) at the Roque de los Muchachos Observatory, La Palma, should help them to show whether this distance is correct. "If the galaxy turns out to be nearer, it will still be a very strange object and offer major challenges to astrophysics," comments Ignacio Trujillo.  The Nube galaxy through different telescopes. Credit: SDSS/GTC/IAC. Another challenge to the present dark matter model? The general rule is that galaxies have a much larger density of stars in their inner regions and that this density falls rapidly with increasing distance from the center. However, Montes says that in Nube, "the density of stars varies very little throughout the object, which is why it is so faint, and we have not been able to observe it well until we had the ultra-deep images from the GTC." Nube has the astronomers puzzled. Prima facie, the team explains, there is no interaction or other indication of its strange properties. Cosmological simulations cannot reproduce its "extreme" characteristics, even on the basis of different scenarios. "We are left without a viable explanation within the currently accepted cosmological model, that of cold dark matter," explains Montes. The cold dark matter model can reproduce the large-scale structures in the universe, but there are small-scale scenarios, such as the case of Nube, for which it cannot give a good answer. We have shown how the different theoretical models cannot produce it, which makes it one of the most extreme cases known until now. "It is possible that with this galaxy, and similar ones which we might find, we can find additional clues which will open a new window on the understanding of the universe," comments Montes. "One possibility, which is attractive, is that the unusual properties of Nube are showing us that the particles that make up dark matter have an extremely small mass," says Ignacio Trujillo. If this were so, this galaxy's unusual properties would demonstrate the properties of quantum physics, but on a galactic scale. "If this hypothesis is confirmed, it would be one of the most beautiful demonstrations of nature, unifying the world of the smallest with that of the largest," he concludes. The research is published in the journal Astronomy & Astrophysics. | |
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| SoupPosted at 2024-01-15 23:48:04(14Wks ago) Report Permalink URL | ||
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| Discovery of second ultra-large structure in distant space further challenges our understanding of the universe by University of Central Lancashire  An artistic impression of what the Big Ring (shown in blue) and Giant Arc (shown in red) would look like in the sky. Credit: Stellarium The discovery of a second ultra-large structure in the remote universe has further challenged some of the basic assumptions about cosmology. The Big Ring in the Sky is 9.2 billion light-years from Earth. It has a diameter of about 1.3 billion light-years, and a circumference of about 4 billion light-years. If we could step outside and see it directly, the diameter of the Big Ring would need about 15 full moons to cover it. It is the second ultra-large structure discovered by University of Central Lancashire (UCLan) Ph.D. student Alexia Lopez who, two years ago, also discovered the Giant Arc in the Sky. Remarkably, the Big Ring and the Giant Arc, which is 3.3 billion light-years across, are in the same cosmological neighborhood—they are seen at the same distance, at the same cosmic time, and are only 12 degrees apart in the sky. Alexia said, "Neither of these two ultra-large structures is easy to explain in our current understanding of the universe. And their ultra-large sizes, distinctive shapes, and cosmological proximity must surely be telling us something important—but what exactly? "One possibility is that the Big Ring could be related to Baryonic Acoustic Oscillations (BAOs). BAOs arise from oscillations in the early universe and today should appear, statistically at least, as spherical shells in the arrangement of galaxies. However, detailed analysis of the Big Ring revealed it is not really compatible with the BAO explanation: The Big Ring is too large and is not spherical." Other explanations might be needed, explanations that depart from what is generally considered to be the standard understanding in cosmology. One possibility might be a different theory—Conformal Cyclic Cosmology (CCC)—which was proposed by Nobel-prize winner Sir Roger Penrose. Rings in the universe could conceivably be a signal of CCC. Another explanation might be the effect of cosmic strings passing through. Cosmic strings are filamentary "topological defects" of great size, which could have been created in the early universe. Another Nobel-prize winner, Jim Peebles, recently hypothesized that cosmic strings could have a role in the origin of some other peculiarities in the large-scale distribution of galaxies. Furthermore, the Big Ring challenges the Cosmological Principle, as did the Giant Arc previously. And if the Big Ring and the Giant Arc together form a still larger structure then the challenge to the Cosmological Principle becomes even more compelling. Such large structures—and there are others found by other cosmologists—challenge our idea of what an "average" region of space looks like. They exceed the size limit of what is considered theoretically viable, and they pose potential challenges to the Cosmological Principle.  The Big Ring is centred close to 0 on the x-axis, spanning roughly -650 to +650 on the x-axis (equivalent to 1.3 billion light years). Credit: University of Central Lancashire Alexia said, "The Cosmological Principle assumes that the part of the universe we can see is viewed as a 'fair sample' of what we expect the rest of the universe to be like. We expect matter to be evenly distributed everywhere in space when we view the universe on a large scale, so there should be no noticeable irregularities above a certain size. "Cosmologists calculate the current theoretical size limit of structures to be 1.2 billion light-years, yet both of these structures are much larger—the Giant Arc is almost three times bigger and the Big Ring's circumference is comparable to the Giant Arc's length. "From current cosmological theories we didn't think structures on this scale were possible. We could expect maybe one exceedingly large structure in all our observable universe. Yet, the Big Ring and the Giant Arc are two huge structures and are even cosmological neighbors, which is extraordinarily fascinating." The Big Ring appears as an almost perfect ring in the sky, but Alexia's further analysis reveals that it has more of a coil shape, like a cork-screw, that is aligned face-on with Earth. The Giant Arc, which is approximately 1/15th the radius of the observable universe, shows as an enormous, nearly symmetrical, crescent of galaxies in the remote universe. It is twice the size of the striking Sloan Great Wall of galaxies and clusters that is seen in the relatively nearby universe. "The Big Ring and Giant Arc are the same distance from us, near the constellation of Boötes the Herdsman, meaning they existed at the same cosmic time when the universe was only half of its present age" commented Alexia. "They are also in the same region of sky, at only 12 degrees apart when observing the night sky. "Identifying two extraordinary ultra-large structures in such close configuration raises the possibility that together they form an even more extraordinary cosmological system. "This data we're looking at is so far away that it has taken half the universe's life to get to us, so from a time when the universe was about 1.8 times smaller than it is now. The Big Ring and the Giant Arc, both individually and together, gives us a big cosmological mystery as we work to understand the universe and its development." Alexia, together with adviser Dr. Roger Clowes, both from UCLan's Jeremiah Horrocks Institute, and collaborator Gerard Williger from the University of Louisville, U.S., discovered the new structure by looking at absorption lines in the spectra of quasars from the Sloan Digital Sky Survey (SDSS). Using the same method that led to the discovery of the Giant Arc, they observed the intervening Magnesium-II (or MgII—it means the atom has lost an electron) absorption systems back-lit by quasars, which are remote super-luminous galaxies. These very distant, very bright, quasars act like giant lamps shining a spotlight through distant, but much fainter, intervening galaxies that otherwise would go unseen. Alexia has presented her findings on the Big Ring at the 243rd meeting of the American Astronomical Society (AAS) on 10 January. | |
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| SoupPosted at 2024-01-17 01:14:29(14Wks ago) Report Permalink URL | ||
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| ALMA observations show how double, triple, quadruple and quintuple star systems form simultaneously in a molecular cloud by Max Planck Society  False-color image of the massive star formation region G333.23–0.06 from data obtained with the ALMA radio observatory. North is to the left. The insets show regions in which Li et al. were able to detect multiple systems of protostars. The star symbols indicate the location of each newly forming stars. The image covers a region 0.62 by 0.78 light-years in size (which on the sky covers a mere 7.5 times 9.5 arc seconds). For comparison: If you look at the sky along an outstretched thumb, it spans a viewing angle of around two degrees. One degree corresponds to 3600 arc seconds. Credit: S. Li, MPIA / J. Neidel, MPIA Graphics Department / Data: ALMA Observatory For humans, the chance of giving birth to multiples is less than 2%. The situation is different with stars, especially with particularly heavy stars. Astronomers observe stars that are many times heavier than the sun in more than 80% of cases in double or multiple systems. The key question is whether they were also born as multiples, or whether stars are born alone and approach each other over time. Multiple births have long been the norm for massive stars. At least on the computer, because in theoretical simulations huge clouds of gas and dust tend to collapse and form multiple systems of massive stars. These simulations depict a hierarchical process in which larger cloud portions contract to form denser cores, and where smaller regions within those "parent cores" collapse to form the separate stars: massive stars, but also numerous less massive stars. And astronomers do indeed find a wealth of fully formed multiple star systems, especially stars that weigh many times more than the sun. However, this does not yet prove that multiple systems with massive stars are already forming in the primordial cloud, as predicted by simulations. ALMA observes a massive star cluster Systematic observations with the ALMA radio observatory, a network of sensitive radio telescopes that can observe the cold molecular gas from which stars are formed at very high resolution, have now shown for the first time that the computer simulations are correct. The images from the ALMA telescope show that a single molecular cloud does not only give rise to binary star systems. They observe the beginnings of a wealth of different multiple systems. Our sun was probably also formed in such a mixture. It is very difficult to observe star formation regions in sufficient detail. Observations had, up to that point, been able to show only a few candidates for isolated multiples in massive star clusters, but nothing like the teeming crowd of multiples predicted by the simulations. In order to confirm or rule out the current models of massive star formation, it was clear that more detailed observations were needed. This became possible once the ALMA observatory in Chile became operational. In its present form, ALMA combines up to 66 radio antennae to act as a single gigantic radio telescope, allowing radio observations that show exquisitely small details. Led by Patricio Sanhueza of the Japanese National Observatory NAOJ and the Graduate University for Advanced Studies in Tokyo, and including several researchers from the Max Planck Institute for Astronomy in Heidelberg, a group of astronomers set out to observe 30 promising massive star-formation regions with ALMA between 2016 and 2019. Analyzing the data proved a considerable challenge, and took several years. Each separate observation yields around 800 GB of data, and reconstructing images from the contributions of all the different antennae is a complex process. The result that has now been published is based on the analysis of one of the star-formation regions, which has the catalogue number G333.23–0.06. The analysis was led by MPIA's Shanghuo Li, who is also the lead author of the resulting paper that has now been published in Nature Astronomy. It is titled "Observations of high-order multiplicity in a high-mass stellar protocluster." The resulting reconstructed images are remarkable: They show details down to about two hundred astronomical units (200 times the Earth-sun distance) for a large region about 200,000 astronomical units across. How stars are forming The results are excellent news for the current picture of massive star formation. In G333.23–0.06, Li and his colleagues found four binary proto-stars, one triple, one quadruple and one quintuple system—consistent with the expectations. In fact, the observations of the environments bolster a particular scenario for high-mass star-formation. They provide evidence for hierarchical star formation, where the gas cloud first fragments into "cores" of increased gas density, and where each core then fragments into a multiple proto-star system. Henrik Beuther, who leads the Star Formation group in the Planet and Star Formation department at the Max Planck Institute for Astronomy, says, "Finally, we were able to take a detailed look at the rich array of multiple star systems in a massive star formation region! Particularly exciting is that the observations go as far as to provide evidence for a specific scenario for high-mass star formation." Shanghuo Li, an astronomer at the Max Planck Institute for Astronomy and the current publication's lead author, adds, "Our observations seem to indicate that when the cloud collapses, the multiples form very early on. But is that really the case? Analyses of additional star formation regions, some of them younger than G333.23–0.06, should give us the answer." Specifically, the astronomers are currently working on a similar analysis for the additional 29 massive star formation regions they had observed—soon to be joined by 20 more, with new ALMA observations led by Li. That should allow farther-reaching statistics on the properties of such regions, and insight into the evolution of the multiples. But even with the present results, the role of multiples in massive star formation is now firmly anchored in observation. Huge explosions and the shaking of space–time Massive stars with more than eight times the mass of the sun, which form multiple star systems, are of particular interest to astronomers: The most massive stars shine much brighter than our sun and are wasteful with their energy supply. They die up to a thousand times earlier than lower-mass stars like our sun. If the star system remains bound after the stars die with supernova explosions, neutron stars and black holes remain, orbiting each other. When black holes merge, they emit gravitational waves, which detectors been able to measure since a few years. Collisions of neutron stars are also particularly exciting. The heaviest elements known to us, such as gold, are demonstrably formed in such kilonovae. | |
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| Jase1Posted at 2024-01-21 18:15:15(13Wks ago) Report Permalink URL | ||
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|  The Hubble Space Telescope has captured an incredible moment in time – the collision of two galaxies. Well, it’s quite a long moment in time, but it is still spectacular. The two galaxies, together known as Arp 122, are a very safe 570 million light-years from Earth, but are racing towards each other at hundreds of thousands of miles an hour. However, when galaxies collide and merge, it can take hundreds of millions of years to actually happen because each is so enormous. In the image, the side-on, slightly warped spiral galaxy NGC 6040 is travelling towards LEDA 59642, another spiral galaxy facing head on. Galaxies are a complex cloud of stars, planets, dust, gas and invisible dark matter. They come in four main types – spiral, elliptical, peculiar and irregular.  When they collide, all of the individual elements experience massive and often violent changes in the gravitational forces around them, which can completely change the structure of the galaxies – or even merge them completely. That may one day happen in the collision captured by Hubble. ‘Galaxies that result from mergers are thought to have a regular or elliptical structure, as the merging process disrupts more complex structures, such as those observed in spiral galaxies,’ said a statement from Nasa. ‘It would be fascinating to know what Arp 122 will look like once this collision is complete… but that will not happen for a long, long time.’ The image also serves as a timely reminder of the incredible discoveries made by Hubble, which is still going strong despite the new James Webb Space Telescope grabbing most of the headlines. And speaking of things closer to home, our own galaxy the Milky Way is actually on a collision course with its nearest neighbour, the Andromeda galaxy, but there’s no need to panic – it will be about four billion years until they meet (although that’s just one billion years before our Sun explodes). | |
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| Jase1Posted at 2024-01-24 11:02:24(13Wks ago) Report Permalink URL | ||
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|  In the summer of 2015 Ignacio Trujillo was sifting through deep-sky images when a slice of constellation Cetus (“whale”) caught his attention. Sourced from a telescope in the universe-mapping Sloan Digital Sky Survey, the snapshot had captured an almost indiscernible “something” that was so obscured by noisy pixels that it could have been a banal artifact or an unremarkable fragment of a passing comet’s tail. But Trujillo, an astronomer at the Institute of Astrophysics of the Canary Islands (IAC) in Spain, had a scintilla of hope that he’d stumbled on something with more cosmic significance. When sharper images from better telescopes arrived nearly four years later, sure enough, a bluish fleck swam into view: a massive, ghostly blob of stars and gas that was so dim that it had escaped the notice of other vigilant astronomers. The supremely puffy galaxy, estimated to be about 300 million light-years away from Earth, is “much extended and larger than what it should be,” Trujillo says. “We’ve not seen anything like that.” Early last year—close to a decade after the galaxy’s first sighting—Trujillo and his colleagues contemplated many names for the new find, looking for one that would commend its extraordinarily diffuse appearance. The Spanish astronomer also showed the images to his five-year-old daughter. “Amelia, what do you think this is?” he asked. “Daddy, this is a Nube,no?” she replied. Nube (pronounced “nooh-bey”) is Spanish for “cloud.” The name was “exactly what we were conceiving,” Trujillo says. He and his colleagues describe the newfound galaxy in a paper recently published in the journal Astronomy & Astrophysics. Follow-up observations, Trujillo says, could soon formally crown Nube as the biggest so-called ultradiffuse galaxy, or UDG—a category of galaxies defined by their very sparse stars and extreme associated faintness. While neither Nube’s colossal size nor its scattered stellar population alone would merit much attention from astronomers, together they reveal a galaxy with a shockingly low and intriguingly uniform distribution of stars. Nube is, for instance, shaped “more like a pancake” than the bulging disk of our own Milky Way, says study lead Mireia Montes of IAC. Yet the galaxy is “so faint you can barely see it.” Most of its mass is thought to lurk in a surrounding halo of dark matter—the invisible substance that binds galaxies together but that researchers have yet to directly detect. The uncanny smoothness of Nube’s diffuse structure, Montes and her colleagues argue, suggests its dark matter halo is similarly plain—a sign that the galaxy and halo alike may be near-pristine relics that have scarcely changed from their formation billions of years ago. That could make Nube an especially valuable test bed for probing the mysterious nature of dark matter. “It’s very rare to find something like this,” says Jin Koda, a professor of physics and astronomy at Stony Brook University, who was not involved with the new paper. “It’s extremely exciting.” A Cosmic Drifter The case for Nube’s cosmic preservation is bolstered by its remote location: the galaxy is adrift in an isolated pocket of the universe, and its closest large neighbor is a whopping 1.4 million light-years away. Observations with the Great Telescope of the Canary Islands (GTC) in Spain suggest that Nube is about 10 billion years old because it hosts some correspondingly elderly stars of that age. Meanwhile an early analysis of 12 hours’ worth of data from the Green Bank Telescope (GBT) in West Virginia suggests the galaxy also hosts a substantial reservoir of primordial hydrogen —the universe’s initial and most abundant element and a fuel that births fresh stars. The galaxy’s abundant hydrogen reservoir suggests Nube is sprouting new generations of stars across eons, according to Ananthan Karunakaran of the University of Toronto, who detected the gas. This blend of old stars and pristine hydrogen in an ultradiffuse galaxy like Nube “isn’t unusual,” he says, “but it’s not typical.” Most UDGs, including more than 800 that Koda and his team found in the Coma Cluster in 2015, are bereft of such hydrogen stores. In the latest data on Nube, the gas shows up like “blips in a heartbeat monitor,” Karunakaran says. GBT’s observations, he notes, weren’t sharp enough to decipher whether the gas is really inside the galaxy or instead located in some more distant galaxy that lurks as yet unseen in the background. Resolving that uncertainty is crucial because the researchers used the hydrogen to estimate Nube’s distance from Earth, which allowed them to infer the galaxy’s enormous size. If the detected hydrogen were just an external imposter, Nube would actually be nearer and thus smaller than otherwise acclaimed. “This whole work hinges on having the correct distance to the galaxy,” says Chris Mihos, an astronomer at Case Western Reserve University, who was not involved with the new paper. “And that’s really hard to measure.” Follow-up observations from the team that are scheduled for the Very Large Array telescope in New Mexico could deliver certainty soon. And if the results are validated, Nube could become a benchmark object for future dark matter studies. “The Billion-Dollar Question” So far, most ultradiffuse galaxies have been spotted interacting with their neighbors in clusters or coasting alongside large galaxies. How, then, did Nube end up as a cosmic drifter? “That’s the billion-dollar question,” says study coauthor Kristine Spekkens of Queen’s University in Ontario. Spekkens says that it’s possible that, like other UDGs, Nube was born into a galaxy group whose residents may have “shaken or stirred” it eons ago, stripping away most of its stars and transforming it into what is called a tidal dwarf galaxy before Nube slipped away. Yet Nube displays no cast-off trails of stars, which are typical for such objects. And it shows no other obvious signs of past interactions with its nearest large neighbor and likely progenitor, the galaxy UGC 929, which lies some 1.4 million light-years in Nube’s rearview. Mihos agrees that Nube doesn’t appear to be a tidal dwarf at first glance. “But that’s not quite the same as saying it never was,” he says. The second, purely hypothetical yet tantalizing possibility is that Nube was simply born weird. Simulations of galaxy formation based on the canonical Lambda-CDM (LCDM) model of cosmology (where “Lambda” and “CDM” mean “dark energy” and “cold dark matter,” respectively) can readily reproduce a wide range of galaxy types with remarkable precision. But they have so far failed to replicate Nube’s “pancake” structure, Montes says. “Even in the more extreme cases, Nube is just way off,” she adds. The galaxy’s eccentric characteristics were replicated very well, however, in simulations that incorporated an alternative leading dark matter candidate called “ultralight axions.” These are hypothetical subatomic particles named for their extremely low mass that, in their gravitational effects, would be barely distinguishable from cold dark matter—save for their subtle smoothing of perturbations in the early universe. Scientists suspect these undiscovered space-pervading particles could be responsible for the universe’s “missing” mass. “Axions are a very exciting candidate beyond the Standard Model of physics,” says Masha Baryakhtar, a theoretical particle physicist at the University of Washington, who was not involved with the new research. “They solve a lot of outstanding problems in the Standard Model.” If axions are dark matter, this may explain how extreme UDGs such as Nube managed to form in apparent isolation from other galaxies, Montes and her colleagues conclude. “That would be amazing—if true,” says Matthew Walker, an astrophysicist at Carnegie Mellon University, who studies dark matter and was not part of the new work. Nube’s defiance of standard cosmological simulations is a “fair claim at this point,” Walker says, although he adds that the galaxy’s weirdness is no guarantee of new physics. “Give them a few years and the simulators figure out how to do it,” he says. “That may well turn out to be the case in this instance, too.” In the meantime, Monte and her team—and undoubtedly others as well—will be scouring the deep sky for more galaxies like Nube in hopes that finding it to be not so unique could nonetheless yield a singular breakthrough in our understanding of the cosmos. | |
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| SoupPosted at 2024-01-24 23:11:21(13Wks ago) Report Permalink URL | ||
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| What could the Extremely Large Telescope see at Proxima Centauri's planet? by Brian Koberlein, Universe Today  Artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri. The double star Alpha Centauri AB is visible to the upper right of Proxima itself. Credit: ESO Proxima Centauri B is the closest exoplanet to Earth. It is an Earth-mass world right in the habitable zone of a red dwarf star just 4 light-years from Earth. It receives about 65% of the energy Earth gets from the sun, and depending on its evolutionary history could have oceans of water and an atmosphere rich with oxygen. Our closest neighbor could harbor life, or it could be a dry rock, but is an excellent target in the search for alien life. There's just one catch. Our usual methods for detecting biosignatures won't work with Proxima Centauri B. Most exoplanets are discovered through the transit method, where a planet regularly passes in front of its star from our point of view. We see the recurring dip in a star's brightness, and we know the planet is there. For transiting exoplanets, we can look for changes in the spectrum of the star as the planet transits. Some of the starlight passes through an exoplanet's atmosphere, and some wavelengths get absorbed by the atmosphere. By looking at the pattern of absorption, we can fingerprint different molecules. This is how we've detected the presence of water, carbon dioxide, and other molecules in exoplanet atmospheres. But Proxima Centauri B isn't a transiting planet. It was discovered by a different method known as Doppler spectroscopy. When we look at the light from Proxima Centauri, we can see its spectrum redshift and blueshift slightly over time. The gravitational pull of Proxima Centauri B makes the star wobble slightly. So we know the exoplanet is there, and have a good idea of its size and mass, but since it doesn't transit its star we can't observe its atmospheric absorption spectrum. But a new study posted to the arXiv preprint server argues there is another way we might find life, using the reflection of starlight off the planet's atmosphere. In principle the idea is simple. Rather than looking for light passing directly through the atmosphere, look instead for light that has reflected off the planet directly. We've done this for planets such as Mars and the outer planets, which don't transit the sun, so we could do it for exoplanets as well.  How different mask designs reveal the orbit of Proxima Centauri B (red dashed circle). Credit: Vaughan et al The problem is that reflected starlight from a planet is tiny compared to the radiance of the star itself. Detecting the reflected light of a planet is like capturing the light of a firefly flittering near the edge of a spotlight. So astronomers have used masks to block the central brilliance of a star and see its family of planets. We have done this to directly observe large gas planets orbiting stars, but not Earth-sized worlds. In this work, the authors look at the potential for the Extremely Large Telescope (ELT), currently under construction in Northern Chile. Specifically, they consider the High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI), which will be able to capture high-resolution spectra on the ELT. The team simulated observations of Proxima Centauri using the masking effect to capture the light of its exoplanet. Is it possible for HARMONI to capture enough high-resolution data to discover biogenic molecules? | |
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| SoupPosted at 2024-01-29 23:18:24(12Wks ago) Report Permalink URL | ||
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| Black hole at the center of a galaxy in the early universe received less mass influx than expected, astronomers find by Max Planck Society  Artist's impression of a quasar whose core region was literally set in motion in the early universe. While galaxies often merged with each other at that time, large amounts of matter were thrown into the centers of the galaxies. When matter orbits the supermassive black hole in the center of a galaxy, energy is released, which explains the enormous brightness of an active galaxy. The quasar can therefore still be observed from a great distance today. Credit: ESO / M. Kornmesser With the upgraded GRAVITY-instrument at the Very Large Telescope Interferometer of the European Southern Observatory, a team of astronomers led by the Max Planck Institute for Extraterrestrial Physics has determined the mass of a black hole in a galaxy only 2 billion years after the Big Bang. With 300 million solar masses, the black hole is actually under-massive compared to the mass of its host galaxy. Researchers suspect what is happening here. A paper on this work is published in the journal Nature. In the more local universe, astronomers have observed tight relationships between the properties of galaxies and the mass of the supermassive black holes residing at their centers, suggesting that galaxies and black holes co-evolve. A crucial test would be to probe this relationship at early cosmic times, but for these far-away galaxies, traditional direct methods of measuring the black hole mass are either impossible or extremely difficult. Even though these galaxies often shine very brightly (they were dubbed "quasars" or "quasi-stellar objects" when they were first discovered in the 1950s), they are so far away that they cannot be resolved with most telescopes. "In 2018, we did the first breakthrough measurements of a quasar's black hole mass with GRAVITY," says Taro Shimizu, staff scientist at the Max Planck Institute for Extraterrestrial Physics. "This quasar was very nearby, however. Now, we have pushed all the way out to a redshift of 2.3, corresponding to a lookback time of 11 billion years."  Illustration of the GRAVITY+ observations of a quasar in the early universe. The background image shows the evolution of the universe since the Big Bang, with the quasar J0920 (artist’s impression) at a lookback time of 11 billion years. The observations were possible by combining all four telescopes of the Very Large Telescope. Credit: T. Shimizu; background image: NASA/WMAP; quasar illustration: ESO/M. Kornmesser; VLT array: ESO/G. Hüdepohl GRAVITY+ now opens a new and precise way to study black hole growth at this critical epoch, often called "cosmic noon," when both black holes and galaxies were rapidly growing. "This is really the next revolution in astronomy—we can now get images of black holes in the early universe, 40 times sharper than possible with the James Webb telescope," points out Frank Eisenhauer, director at the Max Planck Institute for Extraterrestrial Physics, who leads the group developing the GRAVITY instrument and the GRAVITY+ improvements. GRAVITY combines all four 8-meter-telescopes of the ESO Very Large Telescope interferometrically, essentially creating one giant virtual telescope with a diameter of 130 meters. The team was able to spatially resolve the motion of gas clouds around the central black hole of the galaxy, called SDSS J092034.17+065718.0, as they rotate in a thick disk. This allows a direct measurement of the mass of the black hole. With 320 million solar masses, the black hole mass turns out to be actually underweight compared to its host galaxy, which has a mass of about 60 billion solar masses. This suggests that the host galaxy grew faster than the supermassive black hole, indicating a delay between galaxy and black hole growth for some systems. "The likely scenario for the evolution of this galaxy seems to be strong supernova feedback, where these stellar explosions expel gas from the central regions before it can reach the black hole at the galactic center," says Jinyi Shangguan, scientist in the same research group. "The black hole can only start to grow rapidly—and to catch up to the galaxy's growth overall—once the galaxy has become massive enough to retain a gas reservoir in its central regions even against supernova feedback." To determine whether this scenario is also the dominant mode of the co-evolution for other galaxies and their central black holes, the team will follow up with more high-precision mass measurements of black holes in the early universe are needed. | |
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| SoupPosted at 2024-02-01 00:01:56(12Wks ago) Report Permalink URL | ||
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| Webb directly images two planets orbiting white dwarfs by Evan Gough, Universe Today  Artist's rendition of a white dwarf from the surface of an orbiting exoplanet. Astronomers have found two giant planet candidates orbiting two white dwarfs. More proof that giant planets can surve their stars' red giant phases. Credit: Madden/Cornell University In several billion years, our sun will become a white dwarf. What will happen to Jupiter and Saturn when the sun transitions to become a stellar remnant? Life could go on, though the giant planets will likely drift further away from the sun. Stars end their lives in different ways. Some meet their end as supernovae, cataclysmic explosions that destroy any orbiting planets and even sterilize planets light-years away. But only massive stars explode like that. Our sun is not massive enough to explode as a supernova. Instead, it'll spend time as a red giant. The red giant phase occurs when a star runs out of hydrogen to feed fusion. It's a complicated process that astronomers are still working hard to understand. But red giants shed layers of material into space that light up as planetary nebulae. Eventually, the red giant is no more, and only a tiny, yet extraordinarily dense, white dwarf resides in the middle of all the expelled material. Researchers think that some white dwarfs have debris disks around them, out of which a new generation of planets can form. But researchers have also wondered if some planets can survive as stars transition from the main sequence to red giant to white dwarf. Researchers at the Space Telescope Science Institute, Goddard Space Flight Center, and other institutions have found what seem to be two giant planets orbiting two white dwarfs in two different systems. Their research is titled "JWST Directly Images Giant Planet Candidates Around Two Metal-Polluted White Dwarf Stars," and it's in preprint right now on arXiv. The lead author is Susan Mullally, Deputy Project Scientist for JWST. Theoretical thinking shows that exoplanets should exist around white dwarfs. Outer planets beyond where the asteroid belt is in our solar system should survive their star's transition from the main sequence to a red giant to a white dwarf. But stars inside this limit will be engulfed by the red giant as it expands. In our solar system, the sun will likely completely engulf or tidally disrupt and destroy Mercury, Venus, and Earth. Maybe even Mars.  Artist’s impression of a red giant star. As these stars lose mass, they expand and can envelop planets that are too close. Credit: NASA/ Walt Feimer Planets that survive this will likely drift further from the star since the star loses mass and its gravity weakens during the red giant phase. But the problem is that it's difficult to detect planets around white dwarfs. Despite pointed efforts, astronomers have only found a few planetary-mass objects orbiting white dwarfs. As it stands now, Mullally and her colleagues have found two candidate planets around white dwarfs. They're about 11.5 and 34.5 AU from their stars, which are 5.3 billion and 1.6 billion years old. If the planets are as old as the stars, then MIRI photometry shows that the planets are between 1 to 7 Jupiter masses. They could be false positives, but there's only a 1 in 3,000 chance that that's the case. "If confirmed, these would be the first directly imaged planets that are similar in both age and separation to the giant planets in our own solar system, and they would demonstrate that widely separated giant planets like Jupiter survive stellar evolution," the authors write. If the researchers are correct, and the planets formed at the same time as the stars, this is an important leap in our understanding of exoplanets and the stars they orbit. It may also have implications for life on any moons that might be orbiting these planets. But this discovery relates to another issue with white dwarfs: White dwarf metallicity. Some white dwarfs appear to be polluted with metals, elements heavier than hydrogen and helium. Astronomers think that these metals come from asteroids in the asteroid belt, perturbed and sent into the white dwarf by giant planets. "Confirmation of these two planet candidates with future MIRI imaging would provide evidence that directly links giant planets to metal pollution in white dwarf stars," the authors write. Astronomers have found that up to 50% of isolated white dwarfs with hydrogen atmospheres have metals in their photospheres, the stars' surface layer. These white dwarfs must be actively accreting metals from their surroundings. The favored source for these metals is asteroids and comets. "In this scenario, planets that survive the red-giant phase occasionally perturb the orbits of asteroids and comets, which then fall in towards the WD," the authors write.  This artist’s illustration shows rocky debris being drawn toward a white dwarf. Astronomers think that giant planets perturb smaller objects like asteroids and comets inside the WD’s Roche limit. They’re destroyed, and the debris is drawn onto the star’s surface. Credit: NASA, ESA, Joseph Olmsted (STScI) Astronomers have struggled to find planets around WDs. The main methods of finding planets aren't very effective around white dwarfs. The transit method used by Kepler and TESS is ineffective because WDs are so tiny and dim. The other method is the radial velocity method. It senses how a star wobbles due to a planet's influence. It measures the change in the star's spectrum due to the wobbling. However, WDs have nearly featureless spectra, making radial changes difficult to detect. But now we have the JWST. "JWST's infrared capabilities offer a unique opportunity to directly image Jupiter-mass planets orbiting nearby WDs," the researchers write in their paper. The JWST is powerful enough to directly image large planets around tiny stars without using a coronagraph, as long as the planets are far enough away from the star. "Taking advantage of JWST's superb resolution, it is possible to directly image a planet at only a few au from nearby WDs without the use of a coronagraph," Mullally and her colleagues explain. Part of the effort in this work is identifying point sources. In astronomy, a point source is a single, identifiable source of light. Its opposite is a resolved source or an extended source. The researchers had to be confident that what they're seeing around the white dwarfs are point sources, which are mostly likely planets in this case. "We expect these to appear as point sources that increase in brightness at longer wavelengths," they write. To determine if what they're seeing are point sources, astronomers use a process called reference differential imaging. It's a complex procedure, but basically, it involves subtracting the sources from the images. It's especially effective at finding planets close to stars.  This figure from the research explains some of the findings. Each row is a separate white dwarf and planet candidate. In the top row, the large object in the north is a background galaxy unrelated to the research. The researchers went through a process of subtracting and then adding back in both the stars and the giant planet candidates. Credit: Mullally et al. 2024 The figure above shows how the team worked with the images, subtracting both the white dwarf and the candidate planets and identifying the planets as point sources. "In both cases, the candidate is removed cleanly, indicating it is point-source in nature," the authors write. The researchers examined four separate white dwarfs and only two of them have candidate exoplanets. "If confirmed, these two planet candidates provide concrete observational evidence that outer giant planets like Jupiter survive the evolution of low-mass stars," the authors write. Confirmation would also support the idea that 25%–50% of white dwarfs host large planets. That's a big step forward in understanding. But these results unfortunately can't answer another question: Are large planets responsible for sending debris onto the surface of white dwarfs? "The confirmation of these planets are not, however, sufficient to fully validate that large-mass giant planets are the driver of accretion without further observations," writes Mullally and her co-authors. An answer to that question can only come from observing more white dwarfs, especially with the JWST. Hopefully, we won't have to wait long. Last edited by Soup on 2024-02-01 00:05:19 | |
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| Jase1Posted at 2024-02-04 12:24:54(11Wks ago) Report Permalink URL | ||
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|  The billion stars in galaxy UGC 8091 resemble a sparkling snow globe in this festive Hubble Space Telescope image from NASA and ESA (European Space Agency). The dwarf galaxy is approximately 7 million light-years from Earth in the constellation Virgo. It is considered an "irregular galaxy" because it does not have an orderly spiral or elliptical appearance. Instead, the stars that make up this celestial gathering look more like a brightly shining tangle of string lights than a galaxy. Some irregular galaxies may have become tangled by tumultuous internal activity, while others have formed by interactions with neighboring galaxies. The result is a class of galaxies with a diverse array of sizes and shapes, including the diffuse scatter of stars that is this galaxy. Twelve camera filters were combined to produce this image, with light from the mid-ultraviolet through to the red end of the visible spectrum. The red patches are likely interstellar hydrogen molecules that are glowing because they have been excited by the light from hot, energetic stars. The other sparkles on show in this image are a mix of older stars. An array of distant, diverse galaxies appear in the background, captured by Hubble's sharp view. The data used in this image were taken by Hubble's Wide Field Camera 3 and the Advanced Camera for Surveys from 2006 to 2021. Among other things, the observing programs involved in this image sought to investigate the role that dwarf galaxies many billions of years ago had in re-heating the hydrogen that had cooled as the universe expanded after the big bang. Astronomers are also investigating the composition of dwarf galaxies and their stars to uncover the evolutionary links between these ancient galaxies and more modern galaxies like our own. | |
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| Jase1Posted at 2024-02-05 19:17:28(11Wks ago) Report Permalink URL | ||
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|  This new NASA Hubble Space Telescope image shows ESO 185-IG013, a luminous blue compact galaxy (BCG). BCGs are nearby galaxies that show an intense burst of star formation. They are unusually blue in visible light, which sets them apart from other high-starburst galaxies that emit more infrared light. Astrophysicists study BCGs because they provide a relatively close-by equivalent for galaxies from the early universe. This means that BCGs can help scientists learn about galaxy formation and evolution that may have been happening billions of years ago. Hubble imaged ESO 185-IG013 in ultraviolet, visible, and infrared wavelengths to reveal details about its past. Hundreds of young star clusters, many of which are younger than 100 million years, populate the galaxy. A large number of star clusters are only 3.5 million years old – relative infants compared to the timescale of our universe. Scientists predict that many of these youngest clusters will not last, since young clusters can often perish after expelling too much of their gas. The large number of young star clusters indicates that this galaxy was part of a recent galaxy collision and merger. The perturbed structure of the galaxy, which likely occurred from the violent interactions of gas and dust during the collision, is another sign. The merger supplied the system with lots of fuel for star formation, which continues to take place today. ESO 185-IG013 also contains a tidal shell, the diffuse glow surrounding its bright center, which is a common signal of galaxy mergers. Scientists believe that in a galaxy merger, the smaller of the two interacting galaxies gets disrupted by the larger galaxy, losing most of its material. This releases the material, which then gets pulled in again by the gravity of the larger galaxy. The dense area where the material gets repositioned is called the shell, and it contains many star clusters. In addition to the shell, ESO 185-IG013 boasts a tail of gas in the northeast. All of the stars in the system have a combined mass more than 7 billion times that of our Sun. The system is located about 260 million light-years away. | |
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| SoupPosted at 2024-02-07 01:45:27(11Wks ago) Report Permalink URL | ||
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| A long, long time ago in a galaxy not so far away: Research unearths clues to conditions of the early universe by Rutgers University  Two views of a portion of the WLM galaxy, one taken by NASA's Hubble Space Telescope (left), the second by its James Webb Space Telescope. Credit: NASA/ESA/CSA/IPAC/Kristen McQuinn-Rutgers University Employing massive data sets collected through NASA's James Webb Space Telescope, a research team led by a Rutgers University–New Brunswick astronomer is unearthing clues to conditions existing in the early universe. The team has catalogued the ages of stars in the Wolf–Lundmark–Melotte (WLM) galaxy, constructing the most detailed picture of it yet, according to the researchers. WLM, a neighbor of the Milky Way, is an active center of star formation that includes ancient stars formed 13 billion years ago. "In looking so deeply and seeing so clearly, we've been able to—effectively—go back in time," said Kristen McQuinn, an assistant professor in the Department of Physics and Astronomy in the School of Arts and Sciences, who led the research, described in The Astrophysical Journal. "You're basically going on a kind of archaeological dig, to find the very low mass stars that were formed early in the history of the universe." McQuinn credited the Amarel high-performance computing cluster managed by the Rutgers Office of Advanced Research Computing for enabling the team to calculate the galaxy's history of stellar development. One aspect of the research involved taking one massive calculation and repeating it 600 times, McQuinn said. The major computation effort also helped confirm telescope calibrations and data processing procedures that will benefit the wider scientific community, she added. So-called "low mass" galaxies are of special interest to McQuinn. Because they are believed to have dominated the early universe, they allow researchers to study the formation of stars, the evolution of chemical elements and the impact of star formation on the gas and structure of a galaxy. Faint and spread across the sky, they constitute the majority of galaxies in the local universe. Advanced telescopes such as the Webb are allowing scientists a closer look. WLM—an "irregular" galaxy, meaning it doesn't possess a distinct shape, such as a spiral or ellipse—was discovered by the German astronomer Max Wolf in 1909 and characterized in greater detail in 1926 by Swedish astronomer Knut Lundmark and British astronomer Philibert Jacques Melotte. It is positioned at the outskirts of the Local Group, a dumbbell-shaped group of galaxies that includes the Milky Way. Being at the edge of the Local Group has protected WLM from the ravages of intermingling with other galaxies, leaving its star population in a pristine state and useful for study, McQuinn noted. WLM also is interesting to astronomers because it is a dynamic, complex system with lots of gas, enabling it to actively form stars. To formulate the galaxy's star formation history—the rate at which stars have been born across different epochs of time in the universe—McQuinn and her team employed the telescope to painstakingly zero in on swaths of sky containing hundreds of thousands of individual stars. To determine the age of a star, they measured its color—a proxy for temperature—and its brightness. "We can use what we know about stellar evolution and what these colors and brightnesses indicate to basically age the galaxy's stars," said McQuinn, adding the researchers then counted the stars of different ages and mapped out the birth rate of stars over the history of the universe. "What you end up with is a sense of how old this structure is that you're looking at." Cataloging the stars in this way showed the researchers that WLM's star-producing abilities ebbed and flowed over time. The team's observations, which confirm earlier assessments by scientists using the Hubble Space Telescope, show that the galaxy produced stars early in the history of the universe over a period of 3 billion years. It paused for a while, then reignited. McQuinn said she believes that the pause was caused by conditions specific to the early universe. "The universe back then was really hot," she said. "We think the temperature of the universe ended up heating the gas in this galaxy, and kind of turned off star formation for a while. The cool down period lasted a few billion years and then star formation proceeded again." The research is part of NASA's Early Release Program, where designated scientists work with the Space Telescope Science Institute and conduct research designed to highlight Webb's capabilities and help astronomers prepare for future observations. NASA launched the Webb telescope in December 2021. The large-mirrored instrument orbits the sun a million miles away from Earth. Scientists compete for time on the telescope to study a host of topics including the conditions of the early universe, the history of the solar system, and the search for exoplanets. "There's a lot of science that's going to come out of this program that hasn't been done yet," McQuinn said. Other Rutgers researchers on the study included Max Newman, a doctoral student, and Roger Cohen, a postdoctoral associate, both in the Department of Physics and Astronomy, Rutgers School of Arts and Sciences. | |
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| Jase1Posted at 2024-02-07 13:58:53(11Wks ago) Report Permalink URL | ||
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|  Jupiter’s fiery and chaotic moon Io has been imaged in detail by NASA’s Juno spacecraft after another super-close flyby—and this time it caught a volcano or two. Juno, which has been in the Jovian System since 2016 and orbits Jupiter every 38 days, conducted a close flyby of Io on February 3, during which it got to within 930 miles (1,500 kilometers). It comes in the wake of a similarly close flyby on December 30, 2023 during which spectacular close up images were sent back. The two flybys are the closest any spacecraft have made of Io in over 20 years, according to NASA. Here are the stunning first images—including one that shows plumes coming from its hellish surface:  Slightly larger than Earth’s moon, Io has a rocky surface and a tenuous sulfur dioxide atmosphere. Its prominent features include its Pele volcano and Loki Patera, a massive volcanic depression that hosts an ocean of magma. Io is the most volcanic world in the solar system, with eruptions significantly larger than Earth’s. The root cause is its orbit of Jupiter.  Io is the innermost of Jupiter's four so-called Galilean moons—the others being Ganymede, Callisto and Europa—and takes just 42 days to complete an orbit. The gravitational pull of the gas giant planet and its other large moons results in immense heat and frictional tidal heating. That heat creates high volcanic activity and an ocean of magma beneath its rocky surface. In the image, above, you can see two potential plumes, probably of sulfur and sulfur dioxide, being ejected from one or two of Io’s many volcanoes.  Juno’s next perijove (close pass of Jupiter), its 59th, is scheduled to occur on March 7, continuing its exploration of Jupiter. During each perijove, Juno’s elliptical orbit brings it far from Jupiter but then swings it just a few thousand miles from the planet's poles, allowing it to study the cloud tops closely. Juno is the first mission to orbit an outer planet from pole to pole.  Due to Jupiter's intense radiation belts, Juno is equipped with a titanium radiation vault to protect its sensitive scientific instruments, which include a magnetometer, a gravity science system and a microwave radiometer. They help scientists measure Jupiter's magnetic and gravitational fields and its atmospheric temperature, pressure and composition. | |
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| Jase1Posted at 2024-02-08 17:36:26(11Wks ago) Report Permalink URL | ||
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|  Evidence of a deep global ocean beneath the crust of Saturn's moon Mimas—sometimes called the "Death Star"—has surprised astronomers because it's such an unlikely place to find one. A new analysis of observations by the Cassini spacecraft, which explored the Saturn system from 2004 to 2017, indicates that the rocking motion made by Mimas as it orbits—a phenomenon known to astronomers as libration—is caused by a liquid ocean beneath its surface, rather than a completely solid core. The new discovery adds to the handful of verified subsurface oceans in our solar system. It also raises the possibility that life could have evolved there as well. “This is a huge surprise, to be honest,” says astronomer and lead author of the new study Valéry Lainey, who studies the dynamics of Saturn’s moons at the Observatoire de Paris in France. AN UNLIKELY OCEAN WORLD Mimas has been called the "Death Star" because a giant impact crater on one side makes it look like the space station from Star Wars; a crater on Earth of comparable size would be wider than Canada. One of the many moons surrounding Saturn—146 at last count—Mimas is unusual because it rocks heavily from side to side during its orbit around the planet. Such libration could be explained in one of two ways: either Mimas had an extremely elongated core, shaped like a flattened football; or it had a global ocean below its surface. Lainey was part of a team that first proposed Mimas could have a hidden ocean in a 2014 paper in Science. But the idea was largely dismissed, in part because there are no signs of such a thing on its surface—unlike Enceladus, another moon of Saturn, which sprays water from its inner ocean into space. A new paper by the same team, however, published today in Nature, closely studied how the libration changes the orbit of Mimas—and establishes that the moon indeed has a subsurface ocean. The researchers suggest the ocean is kept from freezing by heat from tidal forces during the moon’s orbit around Saturn. And it is a substantial body of water, too: Mimas is relatively small, but its subsurface ocean makes up about half its mass, Lainey says. “Many people will now look at this and say: ‘Oh my gosh, there is truly a global ocean there,’” Lainey says. THE HUNT FOR EXTRATERRESTRIAL LIFE Astronomers had previously found clear signs of subsurface oceans on only two of Saturn’s moons—Enceladus and Titan—and on Jupiter’s moons Europa and Ganymede. As earlier studies noted, where you find liquid water you often find life—and so subsurface oceans are some of the best places to look for extraterrestrial life, which scientists speculate might have evolved around hydrothermal vents from the moons’ cores. The latest research suggests that the ocean on Mimas must be young—between 2 and 25 million years old, which is almost no time at all in celestial terms. That might seem too short a time for life to have evolved there. But Lainey says the ocean on Mimas, which is relatively warm and may have ample supplies of raw chemicals, might be as good a place as any for it to have evolved. He acknowledges, however, that it would be difficult to drill there and find out: although the ocean on Mimas seems very deep—perhaps more than 40 miles deep in some places—its top lies up to 18 miles beneath an outer crust of rock and ice. A HINT AT OCEAN EVOLUTION Mimas could also help scientists understand how other alien oceans developed. The moon is only a little smaller than Enceladus and consists of the same types of rock and ice, Lainey says, which implies that their chemistry and geology are similar. But while the subsurface ocean on Enceladus is about a billion years old, the ocean on Mimas is much younger—perhaps giving scientists a window into the early development of Enceladus, he says. The giant impact crater that makes Mimas look like the Death Star is also a sign that its ocean must be relatively young, says planetary scientist Alyssa Rose Rhoden of the Southwest Research Institute in Boulder. (Explosions may have created weird lakes on Saturn's largest moon.) The crater—named Herschel after astronomer William Herschel, who discovered Mimas in 1789—is thought to have formed hundreds of million years ago when an object several miles across crashed into the moon. Rhoden, who wasn’t involved in the latest study but is a co-author of an article in Nature about it, says the Herschel impact would have punched right through the crust of Mimas if a subsurface ocean had existed; and so the fact that Herschel looks like it does means there was no ocean at the time. THE SEARCH FOR MORE ALIEN OCEANS The discovery also strengthens the idea that subsurface oceans might exist elsewhere in our solar system, particularly on several moons of Uranus and even on some Kuiper Belt objects, which circle the sun beyond Pluto. “It’s a bit different, but yes—you can expect to have liquid water there after all, on many objects,” Lainey says. “Even Mimas, the most unlikely place in the solar system, has a global ocean.” | |
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| SoupPosted at 2024-02-13 01:17:15(10Wks ago) Report Permalink URL | ||
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| Dracula's Chivito: New protoplanetary disk discovered with Pan-STARRS by Tomasz Nowakowski  Color (giy) PS1 image of Dracula's Chivito. Credit: arXiv (2024). DOI: 10.48550/arxiv.2402.01063 By analyzing the images obtained with the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), astronomers have serendipitously discovered a new protoplanetary disk located some 800 light years away. The finding was reported in a paper published February 1 on the pre-print server arXiv. A protoplanetary disk is a disk of dense gas and dust, orbiting a newly formed star. It is assumed that planets are born by the gradual accumulation of material in such a structure, therefore discoveries and studies of protoplanetary disks are essential for improving our understanding of planetary formation processes. Now, a team of astronomers led by Ciprian T. Berghea of the U.S. Naval Observatory (USNO) in Washington, DC, has discovered a new disk of this type that is associated with an infrared source known as IRAS 23077+6707. The finding was made by inspecting the Pan-STARRS data while working on a variability study of active galactic nuclei (AGN) candidates. "We have identified a new, very large protoplanetary disk from PS1 images and confirmed the consistency of available data with a disk interpretation through radiative transfer and SED [spectral energy distribution] modeling," the researchers write in the paper. The newfound protoplanetary disk, dubbed Dracula's Chivito (due to its morphology resembling the chivito sandwich—the national dish of Uruguay), has an apparent size of about 11 arcseconds. This makes it the largest protoplanetary disk so far detected. The mass of Dracula's Chivito was estimated to be around 0.2 solar masses and about 20% of this is in large grains. The disk, which is not associated with any known star-forming region, has an inclination angle of 82 degrees and its radius was calculated to be approximately 1,650 AU. According to the astronomers, the Pan-STARRS images show a late A-type star surrounded by a protoplanetary disk seen almost edge-on, and by an almost dissipated envelope. Therefore, it is likely a young system, still surrounded by a very faint but visible envelope in the northern part. The collected data suggest that the obscured star is two times larger than the sun and has a mass of about 2.5 solar masses. The star has a luminosity of about 11.46 solar luminosities and its effective temperature was estimated to be around 8,000 K. The astronomers also report that Dracula's Chivito showcases the presence of faint "fangs" in the northern part. They interpret them as a dissipating envelope, noting that if this hypothesis is true, it confirms that Dracula's Chivito and its star are a young system at the end of the Class I phase. "It is likely a young system, still surrounded by the envelope which is very faint but still visible in the PS1 images in the northern part," the authors of the paper conclude. | |
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| SoupPosted at 2024-02-15 01:28:40(10Wks ago) Report Permalink URL | ||
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| 'Beyond what's possible': New JWST observations unearth mysterious ancient galaxy by Breck Carter , Swinburne University of Technology  JWST-7329: a rare massive galaxy that formed very early in the Universe. This JWST NIRCAM image shows a red disk galaxy but with images alone it is hard to distinguish from other objects. Spectral analysis of its light with JWST revealed its anomalous nature – it formed around 13 billions years ago even though it contains ~4x more mass in stars than our Milky Way does today. Credit: James Webb Space Telescope Our understanding of how galaxies form and the nature of dark matter could be completely upended after new observations of a stellar population bigger than the Milky Way from more than 11 billion years ago that should not exist. A paper published today in Nature details findings using new data from the James Webb Space Telescope (JWST). The results find that a massive galaxy in the early universe—observed 11.5 billion years ago (a cosmic redshift of 3.2)—has an extremely old population of stars formed much earlier—1.5 billion years earlier in time (a redshift of around 11). The observation upends current modeling, as not enough dark matter has built up in sufficient concentrations to seed their formation. Swinburne University of Technology's Distinguished Professor Karl Glazebrook led the study and the international team, who used the JWST for spectroscopic observations of this massive quiescent galaxy. "We've been chasing this particular galaxy for seven years and spent hours observing it with the two largest telescopes on earth to figure out how old it was. But it was too red and too faint, and we couldn't measure it. In the end, we had to go off Earth and use the JWST to confirm its nature." The formation of galaxies is a fundamental paradigm underpinning modern astrophysics and predicts a strong decline in the number of massive galaxies in early cosmic times. Extremely massive quiescent galaxies have now been observed as early as one to two billion years after the Big Bang which challenges previous theoretical models. Distinguished Professor Glazebrook worked with leading researchers all over the world, including Dr. Themiya Nanayakkara, Dr. Lalitwadee Kawinwanichakij, Dr. Colin Jacobs, Dr. Harry Chittenden, Associate Professor Glenn G Kacprzak and Associate Professor Ivo Labbe from Swinburne's Centre for Astrophysics and Supercomputing. "This was very much a team effort, from the infrared sky surveys we started in 2010 that led to us identifying this galaxy as unusual, to our many hours on the Keck and Very Large Telescope where we tried, but failed to confirm it, until finally the last year where we spent enormous effort figuring out how to process the JWST data and analyze this spectrum." Dr. Themiya Nanayakkara, who led the spectral analysis of the JWST data, says, "We are now going beyond what was possible to confirm the oldest massive quiescent monsters that exist deep in the universe. This pushes the boundaries of our current understanding of how galaxies form and evolve. The key question now is how they form so fast very early in the universe, and what mysterious mechanisms lead to stopping them forming stars abruptly when the rest of the universe doing so." Associate Professor Claudia Lagos from The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR) was crucial in developing the theoretical modeling of the evolution of dark matter concentrations for the study. "Galaxy formation is in large part dictated by how dark matter concentrates," she says. "Having these extremely massive galaxies so early in the universe is posing significant challenges to our standard model of cosmology. This is because we don't think such massive dark matter structures as to host these massive galaxies have had time yet to form. More observations are needed to understand how common these galaxies may be and to help us understand how truly massive these galaxies are." Glazebrook hopes this could be a new opening for our understanding of the physics of dark matter, stating, "JWST has been finding increasing evidence for massive galaxies forming early in time. This result sets a new record for this phenomenon. Although it is very striking, it is only one object. But we hope to find more, and if we do, this will really upset our ideas of galaxy formation." | |
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| SoupPosted at 2024-02-21 01:20:20(9Wks ago) Report Permalink URL | ||
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| The brightest object in the universe is a black hole that eats a star a day by Christian Wolf, The Conversation  The brightest thing in the universe: J0529-4351 is a glowing disc of matter around a supermassive black hole, and it is 500 trillion times brighter than the sun. (The red dot is a neighboring star.) Dark Energy Camera Legacy Survey DR10 / Nature Astronomy, CC BY-SA Scientists have now reported evidence of the true conditions in Hell, perhaps because no one has ever returned to tell the tale. Hell has been imagined as a supremely uncomfortable place, hot and hostile to bodily forms of human life. Thanks to a huge astronomical survey of the entire sky, we have now found what may be the most hellish place in the universe. In a new paper in Nature Astronomy, we describe a black hole surrounded by the largest and brightest disk of captive matter ever discovered. The object, called J0529-4351, is therefore also the brightest object found so far in the universe. Supermassive black holes Astronomers have already found around one million fast-growing supermassive black holes across the universe, the kind that sit at the centers of galaxies and are as massive as millions or billions of suns. To grow rapidly, they pull stars and gas clouds out of stable orbits and drag them into a ring of orbiting material called an accretion disk. Once there, very little material escapes; the disk is a mere holding pattern for material that will soon be devoured by the black hole. The disk is heated by friction as the material in it rubs together. Pack in enough material and the glow of the heat gets so bright that it outshines thousands of galaxies and makes the black hole's feeding frenzy visible to us on Earth, more than 12 billion light years away. The fastest-growing black hole in the universe The accretion disk of J0529-4351 emits light that is 500 trillion times more intense than that of our sun. Such a staggering amount of energy can only be released if the black hole eats about a sun worth of material every day. It must also have a large mass already. Our data indicate J0529-4351 is 15 to 20 billion times the mass of our sun. There is no need to be afraid of such black holes. The light from this monster has taken more than 12 billion years to reach us, which means it would have stopped growing long ago. In the nearby universe, we see that supermassive black holes these days are mostly sleeping giants. Black holes losing their grip The age of the black hole feeding frenzy is over because the gas floating around in galaxies has mostly been turned into stars. And after billions of years the stars have sorted themselves into orderly patterns: they are mostly on long, neat orbits around the black holes that sleep in the cores of their galaxies. Even if a star dove suddenly down towards the black hole, it would most likely carry out a slingshot maneuver and escape again in a different direction. Space probes use slingshot maneuvers like this to get a boost from Jupiter to access hard-to-reach parts of the solar system. But imagine if space were more crowded, and our probe ran into one coming the other way: the two would crash together and explode into a cloud of debris that would rapidly fall into Jupiter's atmosphere. Such collisions between stars were commonplace in the disorder of the young universe, and black holes were the early beneficiaries of the chaos. Accretion disks: A no-go zone for space travelers Accretion disks are gateways to a place whence nothing returns, but they are also profoundly unfriendly to life in themselves. They are like giant storm cells, whose clouds glow at temperatures reaching several tens of thousands of degrees Celsius. The clouds are moving faster and faster as we get closer to the hole, and speeds can reach 100,000 kilometers per second. They move as far in a second as the Earth moves in an hour. The disk around J0529-4351 is seven light years across. That is one and a half times the distance from the sun to its nearest neighbor, Alpha Centauri. Why only now? If this is the brightest thing in the universe, why has it only been spotted now? In short, it's because the universe is full of glowing black holes. The world's telescopes produce so much data that astronomers use sophisticated machine learning tools to sift through it all. Machine learning, by its nature, tends to find things that are similar to what has been found before. This makes machine learning excellent at finding run-of-the-mill accretion disks around black holes—roughly a million have been detected so far—but not so good at spotting rare outliers like J0529-4351. In 2015, a Chinese team almost missed a remarkably fast-growing black hole picked out by an algorithm because it seemed too extreme to be real. In our recent work, we were aiming to find all the most extreme objects, the most luminous and most rapidly growing black holes, so we avoided using machine learning tools that were guided by too much prior knowledge. Instead we used more old-fashioned methods to search through new data covering the entire sky, with excellent results. Our work also depended on Australia's current 10-year partnership with the European Southern Observatory. | |
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| SoupPosted at 2024-02-21 23:37:52(9Wks ago) Report Permalink URL | ||
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| JWST sees a Milky Way-like galaxy coming together in the early universe by Evan Gough, Universe Today  This image shows the Firefly Sparkle galaxy and its two neighbours, BF and NBF. The Firefly Sparkle’s mass is concentrated in 10 clusters that contain up to 57% of its entire mass. Credit: Mowla et al. 2024. The gigantic galaxies we see in the universe today, including our own Milky Way galaxy, started out far smaller. Mergers throughout the universe's 13.7 billion years gradually assembled today's massive galaxies. But they may have begun as mere star clusters. In an effort to understand the earliest galaxies, the JWST has examined their ancient light for clues as to how they became so massive. The JWST can effectively see back in time to when the universe was only about 5% as old as it is now. In that distant past, structures that would eventually become as massive as the Milky Way, and even larger, were only about 1/10,000th as massive as they are now. What clues can the powerful infrared space telescope uncover that show us how galaxies grew so large? A new paper presents JWST observations of a galaxy at redshift z~8.3. At that redshift, the light has been traveling for over 13 billion years and began its journey only 600 million years after the Big Bang. The galaxy, called the Firefly Sparkle, contains a network of massive star clusters that are evidence of how galaxies grow. The paper is "The Firefly Sparkle: The Earliest Stages of the Assembly of A Milky Way-type Galaxy in a 600 Myr Old Universe." The lead author is Lamiya Mowla, an observational astronomer and assistant professor of Physics and Astronomy at Wellesley College. The paper is in preprint on arXiv and hasn't yet been peer-reviewed.  The ancient Firefly Sparkle galaxy is precursor to galaxies like the Milky Way. The JWST found ten separate clusters in the galaxy that show how the galaxy is growing through mergers. Credit: Mowla et al. 2024. Despite the JWST's power, this distant, ancient galaxy is only visible through the gravitational lensing of a massive cluster of foreground galaxies. The lensing makes the Firefly Sparkle appear as an arc. Two other galaxies are also in the vicinity, called Firefly BF (Best Friend) and Firefly NBF (New Best Friend.) "The Firefly Sparkle exhibits the hallmarks expected of a future Milky Way–type galaxy captured during its earliest and most gas-rich stage of formation," the authors write. The young galaxy's mass is concentrated in 10 clusters, which range from about 200,000 solar masses to 630,000 solar masses. According to the authors, these clusters "straddle the boundary between low-mass galaxies and high-mass globular clusters." These clusters are significant because they're clues to how the galaxy is growing. The researchers were able to gauge the ages of the clusters and their star formation histories. They found that they experienced a burst of star formation at around the same time. "The cluster ages suggest that they are gravitationally bound with star formation histories showing a recent starburst possibly triggered by the interaction with a companion galaxy at the same redshift at a projected distance of ~2 kpc away from the Firefly Sparkle." There are two candidates for the interacting galaxy: Firefly Best Friend (BF) and Firefly New Best Friend (NBF). But NBF is about 13 kpcs away, while BF is about two kpcs away, making BF the likely interactor. "Faint low-surface brightness features are visible at the corners of the arc close to the neighbor, hinting at a possible interaction between the two galaxies [FS and BF] which may have triggered a burst of star formation in both of them," explain the researchers. The researchers paid special attention to the central cluster. They found that the temperature is extremely high at about 40,000 Kelvin (40,000°C; 72,000°F.) It also has a top-heavy initial mass function, a signal that it formed in a very metal-poor environment. These observations and other evidence show that Firefly Sparkle is very likely a progenitor of galaxies like ours. For these reasons, "… the Firefly Sparkle provides an unprecedented case study of a Milky Way-like galaxy in the earliest stages of its assembly in only a 600 million-year-old universe," the authors write.  This figure compares Firefly Sparkle’s current mass with the TNG 50 simulations of galaxy growth and with the growth rate of the Milky Way, according to an upcoming paper. Credit: Mowla et al. 2024 Fortunately, the researchers behind these results have a powerful supercomputer simulation to compare observations with. It's called Illustris TNG. It's a massive cosmological magnetohydrodynamical simulation based on a comprehensive physical model of the universe. Illustris TNG has made three runs, called TNG50, TNG 100, and TNG 300. The researchers compared their results with TNG 50. Finding these ancient star clusters is intriguing, but we can't assume they'll survive intact. There are tidal and evaporative forces at work. The authors examined the stability of the individual star clusters and how they'll fare over time. "Most of these star clusters are expected to survive to the present-day universe and will expand and then get ripped apart to form the stellar disk and the halo of the galaxy," the authors explain. "The only way they survive is to get kicked out to large distances, away from the dense tidal field of the galaxy." The ones that get kicked out may persist as globular clusters. One of the JWST's primary science goals is to study how galaxies formed and evolved in the early universe. By finding one in which clusters are still forming, the space telescope is reaching its goal. "The Firefly Sparkle represents one of JWST's first spectrophotometric observations of an extremely lensed galaxy assembling at high redshifts, with clusters that are in the process of formation instead of seen at later epochs," the authors conclude. | |
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| SoupPosted at 2024-03-13 00:25:45(6Wks ago) Report Permalink URL | ||
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| Dark Energy Camera captures remains of a massive star that exploded nearly 11,000 years ago in huge gigapixel image by Josie Fenske, Inter-American Observatory  With the powerful, 570-megapixel Department of Energy-fabricated Dark Energy Camera (DECam), astronomers have constructed a massive 1.3-gigapixel image showcasing the central part of the Vela Supernova Remnant, the cosmic corpse of a gigantic star that exploded as a supernova. DECam is one of the highest-performing wide-field imaging instruments in the world and is mounted on the US National Science Foundation's Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory, a Program of NSF’s NOIRLab. Credit: Inter-American Observatory This colorful web of wispy gas filaments is the Vela Supernova Remnant, an expanding nebula of cosmic debris left over from a massive star that exploded about 11,000 years ago. Located around 800 light-years away in the constellation Vela (the Sails), this nebula is one of the nearest supernova remnants to Earth. Though the unnamed star ended its life thousands of years ago, the shockwave its death produced is still propagating into the interstellar medium, carrying glowing tendrils of gas with it. This image is one of the biggest ever made of this object and was taken with the state-of-the-art wide-field Dark Energy Camera (DECam), built by the Department of Energy and mounted on the US National Science Foundation's Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF's NOIRLab. The striking reds, yellows, and blues in this image were achieved through the use of three DECam filters that each collect a specific color of light. Separate images were taken in each filter and then stacked on top of each other to produce this high-resolution color image that showcases the intricate web-like filaments snaking throughout the expanding cloud of gas. This is also the largest DECam image ever released publicly, containing an astounding 1.3 gigapixels. The Vela Supernova Remnant is merely the ghost of a massive star that once was. When the star exploded 11,000 years ago, its outer layers were violently stripped away and flung into the surrounding region, driving the shockwave that is still visible today. As the shockwave expands into the surrounding region, the hot, energized gas flies away from the point of detonation, compressing and interacting with the interstellar medium to produce the stringy blue and yellow filaments seen in the image. The Vela Supernova Remnant is a gigantic structure, spanning almost 100 light-years and extending to twenty times the diameter of the full moon in the night sky. Despite the dramatics of the star's final moments, it wasn't entirely wiped from existence. After shedding its outer layers, the core of the star collapsed into a neutron star—an ultra-dense ball consisting of protons and electrons that have been smashed together to form neutrons. The neutron star, named the Vela Pulsar, is now an ultra-condensed object with the mass of a star like the sun contained in a sphere just a few kilometers across. Located in the lower left region of this image, the Vela Pulsar is a relatively dim star that is indistinguishable from its thousands of celestial neighbors. Still reeling from its explosive death, the Vela Pulsar spins rapidly on its own axis and possesses a powerful magnetic field. These properties result in twin beams of radiation that sweep the sky 11 times per second, just like the consistent blips of a rotating lighthouse bulb. This high-quality image demonstrates the incredibly deep and wide capabilities of DECam. From its vantage point in the Chilean Andes, the Blanco telescope receives light that has traveled across the universe. After entering the telescope's tube, the light is reflected by a mirror 4 meters (13 feet) wide—a massive, aluminum-coated, and precisely shaped piece of glass roughly the weight of a semi-truck. The light is then guided into the optical innards of DECam, passing through a corrective lens nearly a meter (3.3 feet) across before falling on a grid of 62 charge-coupled devices (CCDs), which act like the 'eyes' of the camera. The incoming light is then converted into electrical signals, which are read out as pixels. A single image taken with DECam has 570 megapixels, so with multiple exposures stacked on top of one another, the amount of detail that can be captured is truly remarkable. Owing to DECam's large mosaic of CCDs, astronomers are able to create mesmerizing images of faint astronomical objects, such as the Vela Supernova Remnant, that offer a limitless starscape to explore. Provided by Inter-American Observatory | |
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| SoupPosted at 2024-04-02 01:44:09(3Wks ago) Report Permalink URL | ||
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| Distant 'space snowman' unlocks mystery of how some dormant deep space objects become 'ice bombs' by Brown University  This image was taken by NASA's New Horizons spacecraft on Jan. 1, 2019 during a flyby of Kuiper Belt object 2014 MU69. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute A new study is shaking up what scientists thought they knew about distant objects in the far reaches of the solar system, starting with an object called the space snowman. Researchers from Brown University and the SETI Institute found that the double-lobed object, which is officially named Kuiper Belt Object 486958 Arrokoth and resembles a snowman, may have ancient ices stored deep within it from when the object first formed billions of years ago. But that's just the beginning of their findings. Using a new model they developed to study how comets evolve, the researchers suggest this feat of perseverance isn't unique to Arrokoth but that many objects from the Kuiper Belt—which lies at the outermost regions of the solar system and dates back to the early formation of the solar system around 4.6 billion years ago—may also contain the ancient ices they formed with. "We've shown here in our work, with a rather simple mathematical model, that you can keep these primitive ices locked deep within the interiors of these objects for really long times," said Sam Birch, a planetary scientist at Brown and one of the paper's co-authors. "Most of our community had thought that these ices should be long lost, but we think now that may not be the case." Birch describes the work in the journal Icarus with co-author Orkan Umurhan, a senior research scientist at the SETI Institute. Until now, scientists had a hard time figuring out what happens to ices on these space rocks over time. The study challenges widely used thermal evolutionary models that have failed to account for the longevity of ices that are as temperature sensitive as carbon monoxide. The model the researchers created for the study accounts for this change and suggests that the highly volatile ices in these objects stick around much longer than was previously thought. "We are basically saying that Arrokoth is so super cold that for more ice to sublimate—or go directly from solid to a gas, skipping the liquid phase within it—that the gas it sublimates into first has to have travel outwards through its porous, sponge-like interior," Birch said. "The trick is that to move the gas, you also have to sublimate the ice, so what you get is a domino effect: it gets colder within Arrokoth, less ice sublimates, less gas moves, it gets even colder, and so on. Eventually, everything just effectively shuts off, and you're left with an object full of gas that is just slowly trickling out." The work suggests that Kuiper Belt objects can act as dormant "ice bombs," preserving volatile gases within their interiors for billions of years until orbital shifts bring them closer to the sun and the heat makes them unstable. This new idea could help explain why these icy objects from the Kuiper Belt erupt so violently when they first get closer to the sun. All of a sudden, the cold gas inside them rapidly gets pressurized and these objects evolve into comets. "The key thing is that we corrected a deep error in the physical model people had been assuming for decades for these very cold and old objects," said Umurhan, Birch's co-author on the paper. "This study could be the initial mover for reevaluating the comet interior evolution and activity theory." Altogether, the study challenges existing predictions and opens up new avenues for understanding the nature of comets and their origins. Birch and Umurhan are co-investigators in NASA's Comet Astrobiology Exploration Sample Return (CAESAR) mission to acquire at least 80 grams of surface material from the comet 67P/Churyumov-Gerasimenko and return it to Earth for analysis. The results from this study could help guide CAESAR's exploration and sampling strategies, helping to deepen our understanding of cometary evolution and activity. "There may well be massive reservoirs of these primitive materials locked away in small bodies all across the outer solar system—materials that are just waiting to erupt for us to observe them or sit in deep freeze until we can retrieve them and bring them home to Earth," Birch said. | |
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