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  • Galaxy collision could send solar system flying
    Montag, 07.01.2019, 05:59:02 Uhr
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    Galaxy collision could send solar system flying Durham UK (SPX) Jan 04, 2019 -
    A nearby galaxy is hurtling towards the Milky Way on a collision course that could fling our solar system into interstellar space.New research led by astrophysicists at Durham University, UK, predicts that the Large Magellanic Cloud (LMC) could hit the Milky Way in two billion years' time. The collision could occur much earlier than the predicted impact between the Milky Way and another neighbouring galaxy, Andromeda, which scientists say will hit our galaxy in eight billion years.The catastrophic coming together with the Large Magellanic Cloud could wake up our galaxy's dormant black hole, which would begin devouring surrounding gas and increase in size by up to ten times.As it feeds, the now-active black hole would throw out high-energy radiation and while these cosmic fireworks are unlikely to affect life on Earth, the scientists say there is a small chance that the initial collision could send our solar system hurtling into space.The findings are published Jan 4 in the journal Monthly Notices of the Royal Astronomical Society.Galaxies like our own Milky Way are surrounded by a group of smaller satellite galaxies that orbit around them, in a similar way to how bees move around a hive. Typically, these satellite galaxies have a quiet life and orbit around their hosts for many billions of years. However, from time to time, they sink to the centre, collide and are devoured by their host galaxy.The Large Magellanic Cloud is the brightest satellite galaxy of the Milky Way and only entered our neighbourhood about 1.5 billion years ago. It sits about 163,000 light-years from the Milky Way. Until recently astronomers thought that it would either orbit the Milky Way for many billions of years, or, since it moves so fast, escape from our galaxy's gravitational pull.However, recent measurements indicate that the Large Magellanic Cloud has nearly twice as much dark matter than previously thought. The researchers say that since it has a larger than expected mass, the Large Magellanic Cloud is rapidly losing energy and is doomed to collide with our galaxy.The research team, led by scientists at Durham University's Institute for Computational Cosmology working with the University of Helsinki, in Finland, used the EAGLE galaxy formation supercomputer simulation to predict the collision.Lead author Dr. Marius Cautun, a postdoctoral fellow in Durham University's Institute for Computational Cosmology, said: "While two billion years is an extremely long time compared to a human lifetime, it is a very short time on cosmic timescales."The destruction of the Large Magellanic Cloud, as it is devoured by the Milky Way, will wreak havoc with our galaxy, waking up the black hole that lives at its centre and turning our galaxy into an 'active galactic nucleus' or quasar."This phenomenon will generate powerful jets of high energy radiation emanating from just outside the black hole. While this will not affect our solar system, there is a small chance that we might not escape unscathed from the collision between the two galaxies which could knock us out of the Milky Way and into interstellar space."The collision between the Large Magellanic Cloud and the Milky Way could be spectacular, the researchers say.Co-author Professor Carlos Frenk, Director of the Institute for Computational Cosmology, Durham University, said: "Beautiful as it is, our universe is constantly evolving, often through violent events like the forthcoming collision with the Large Magellanic Cloud."Barring any disasters, like a major disturbance to the solar system, our descendants, if any, are in for a treat: a spectacular display of cosmic fireworks as the newly awakened supermassive black hole at the centre of our galaxy reacts by emitting jets of extremely bright energetic radiation."According to the researchers, the merger of the two galaxies could be long overdue in cosmic terms.Dr. Alis Deason, of Durham University's Institute for Computational Cosmology, said: "We think that up to now our galaxy has had only a few mergers with very low mass galaxies. This represents very slim pickings when compared to nearby galaxies of the same size as the Milky Way."For example, our nearest neighbour, the Andromeda galaxy, devoured galaxies weighing nearly 30 times more than those consumed by the Milky Way. Therefore, the collision with the Large Magellanic Cloud is long overdue and it is needed to make our galaxy typical."Research Report: "The Aftermath of the Great Collision Between Our Galaxy and the Large Magellanic Cloud," M. Cautun et al., 2019 Jan. 4, Monthly Notices of The Royal Astronomical Society
  • Early protostar already has a warped disk
    Montag, 07.01.2019, 05:59:02 Uhr
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    Early protostar already has a warped disk Saitami, Japan (SPX) Jan 01, 2019 -
    Using observations from the ALMA radio observatory in Chile, researchers have observed, for the first time, a warped disk around an infant protostar that formed just several tens of thousands of years ago. This implies that the misalignment of planetary orbits in many planetary systems - including our own - may be caused by distortions in the planet-forming disk early in their existence.The planets in our solar system orbit the Sun in planes that are at most about seven degrees offset from the equator of the Sun itself. It has been known for some time that many extrasolar systems have planets that are not lined up in a single plane or with the equator of the star.One explanation for this is that some of the planets might have been affected by collisions with other objects in the system or by stars passing by the system, ejecting them from their initial orbital plane.However, the possibility remained that the formation of planets out of the normal plane was actually caused by a warping of the star-forming cloud out of which the planets were born. Recently, images of protoplanetary disks - rotating disks where planets form around a star - have in fact showed such warping. But it was still unclear how early this happened.In the latest findings, published in Nature, the group from the RIKEN Cluster for Pioneering Research (CPR) and Chiba University in Japan have discovered that L1527; an infant protostar still embedded within a cloud, has a disk that has two parts - an inner one rotating in one plane, and an outer one in a different plane.The disk is very young and still growing. L1527, which is about 450 light-years away in the Taurus Molecular Cloud, is a good object for study as it has a disk that is nearly edge-on to our view.According to Nami Sakai, who led the research group, "This observation shows that it is conceivable that the misalignment of planetary orbits can be caused by a warp structure formed in the earliest stages of planetary formation. We will have to investigate more systems to find out if this is a common phenomenon or not."The remaining question is what caused the warping of the disk. Sakai suggests two reasonable explanations."One possibility," she says, "is that irregularities in the flow of gas and dust in the protostellar cloud are still preserved and manifest themselves as the warped disk. A second possibility is that the magnetic field of the protostar is in a different plane from the rotational plane of the disk, and that the inner disk is being pulled into a different plane from the rest of the disk by the magnetic field." She says they plan further work to determine which is responsible for the warping of the disk.Research Report: "Warped Disk Around an Infant Protostar," Nami Sakai, Tomoyuki Hanawa, Yichen Zhang, Aya E. Higuchi, Satoshi Ohashi, Yoko Oya and Satoshi Yamamoto, 2018 Dec. 31, Nature
  • Baby Star's Fiery Tantrum Could Create Building Blocks of Planets
    Montag, 07.01.2019, 05:59:02 Uhr
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    Baby Star's Fiery Tantrum Could Create Building Blocks of Planets Warwick UK (SPX) Jan 01, 2019 -
    A massive stellar flare on a baby star has been spotted by University of Warwick astronomers, shedding light on the origins of potentially habitable exoplanets.One of the largest ever seen on a star of its type, the huge explosion of energy and plasma is around 10,000 times bigger than the largest solar flare ever recorded from our own Sun.The discovery is detailed in a paper for the Monthly Notices of the Royal Astronomical Society and reveals how this huge 'tantrum' could even perturb the material orbiting a star which would create the building blocks for future planets.The flare was seen on a young M-type star named NGTS J121939.5-355557, located 685 light-years away. At around 2 million years old, it is what astronomers refer to as a pre-main sequence star which is yet to reach the size that it spends the majority of its lifecycle.It was observed as part of a large flare survey of thousands of stars by University of Warwick PhD student James Jackman, as part of a project searching for explosive phenomena on stars outside our solar system. He used the Warwick-led Next-Generation Transit Survey (NGTS) telescope array in Chile which is designed to find exoplanets by collecting brightness measurements of hundreds of thousands of stars and is based at the European Southern Observatory's Paranal Observatory. His attention was drawn to NGTS J121939.5-355557 as it had one of the largest flares seen in these types of stars.A stellar flare occurs when the magnetic field of a star rearranges itself, releasing huge amounts of energy in the process. This accelerates charged particles, or plasma, within the star which crash into its surface, heating it up to around 10,000 degrees. That energy produces optical and infrared light, but also X-rays and gamma rays that can be picked up by telescopes on Earth and in orbit.Magnetic fields on M stars are a lot stronger than those on our own Sun and the astronomers calculated that this size of flare is a rare event, occurring anywhere from every three years to twice a decade.James, who is studying in the University of Warwick's Department of Physics, said: "This is normally a star that shows little activity and stays a constant brightness. Then, on this one particular night, we saw it suddenly grow seven times brighter than normal for a few hours, which is pretty extreme. And then after that it goes back to normal."We see these types of flares on the Sun, but nowhere near as big as this. On our Sun, you can do incredibly detailed studies on this kind of activity. It's difficult to extend that understanding to other stars because the data we need hasn't been available until now."This is an incredibly young star, only about 2 million years old. You'd call it a baby - it's going to live for tens of billions of years, so it's in the first one percent of its lifetime. Even though it's much cooler than our Sun by about 2,000 degrees it is roughly the same size, but pretty large for an M star. This is because it's still being formed from gas in the disc and contracting and cooling until it reaches the main sequence, staying at a certain radius and luminosity for billions of years."Finding out these kinds of details has only been possible thanks to the Gaia mission that began earlier this year."The X-rays from these large flare events are thought to affect the formation of 'chondrules,' flash-melted calcium-aluminium-rich grains in the star's protoplanetary disc. These gather together into asteroids that eventually coalesce into orbiting planets. The study adds to our understanding of how flares 'perturb' the protoplanetary disc, moving around the material that impacts on planet formation and affecting the eventual structure of a planetary system.Professor Peter Wheatley, James's PhD supervisor, said: "A massive flare like this could be advantageous for planet formation, or it could be disruptive. This particular star won't have formed its planets yet so this type of flare activity is something that astronomers will need to take into account when considering planet formation."There's a discussion at the moment around whether flares are a good or bad thing for life on orbiting habitable planets, because they output a large amount of UV radiation. That could cause biological damage to surface organisms and damage their DNA. On the other hand, UV radiation is required for various chemical reactions to start life and that's not typically provided in great enough quantity by these types of stars. These flares could potentially kickstart these reactions."Research Report: "Detection of a Giant Flare Displaying Quasi-Periodic Pulsations from a Pre-Main Sequence M Star by the Next Generation Transit Survey," James A. G. Jackman et al., 2018 Dec. 1, Monthly Notices of the Royal Astronomical Society
  • Scientists discover how and when DNA replicates
    Montag, 07.01.2019, 05:59:02 Uhr
    Scientists discover how and when DNA replicates Washington (UPI) Jan 01, 2019 -

    Scientists have discovered how and when DNA replicates inside cells.

    Researchers first identified DNA replication in the 1950s, but have since struggled to understand the underlying mechanisms.

    "It's been quite a mystery," David Gilbert, professor of molecular biology at Florida State University, said in a news release. "Replication seemed resilient to everything we tried to do to perturb it. We've described it in detail, shown it changes in different cell types and that it is disrupted in disease. But until now, we couldn't find that final piece, the control elements or the DNA sequences that control it."

    In an attempt to disrupt the replication's timing, Gilbert and doctoral student Jiao Sima engineered dozens of genetic mutations on DNA molecules. The experiments failed to provide insight.

    In what the researchers described as a "Hail Mary" approach, Gilbert and Sima studied a single DNA segment in the highest 3D resolution possible. Their analysis revealed three sequences regularly in contact with each other around a DNA molecule.

    Using CRISPR, scientists deleted the three sequences simultaneously. To their surprise and relief, the deletion interrupted DNA replication and altered the DNA molecule's structure.

    "Removing these elements shifted the segment's replication time from the very beginning to the very end of the process," Gilbert said. "This was one of those moments where just one result knocks your socks off."

    Researchers described their breakthrough in the journal Cell.

    "We have for the first time pinpointed specific DNA sequences in the genome that regulate chromatin structure and replication timing," Sima said. "These results reflect one possible model of how DNA folds inside cells and how these folding patterns could impact the hereditary materials' function."

    Researchers think the disruption of DNA replication could explain the development of certain diseases.
  • NASA study finds sugars, key ingredient for life, can form in space
    Montag, 07.01.2019, 05:59:02 Uhr
    NASA study finds sugars, key ingredient for life, can form in space Washington DC (Sputnik) Dec 21, 2018 -
    A new study by NASA scientists has proven that sugar molecules - one of the building blocks of life - can form in conditions similar to those in outer space. The find provides further grist to the mill of the argument that life on Earth got some sort of help from above in its formation.A new paper published on Tuesday by scientists from the National Atmospheric and Space Administration's (NASA) Ames Research Center in the journal Nature Communications proves that a sugar molecule key to the formation of life can form in the extremely cold and radiation-rich conditions of outer space.The scientists recreated the conditions of space by cooling aluminum substrate to -440 degrees Fahrenheit, close to absolute zero, and placing it in a vacuum chamber, into which they pumped a mixture of water and methanol gas, similar to that found in the interstellar medium. They then bathed the sample in ultraviolet light to simulate stellar radiation.At first, ice built up on the sample, but the UV light melted it. But what scientists found after was the real prize: a small amount of 2-deoxyribose - the "D" in "DNA" - had formed, along with several other kinds of sugar molecules, on the surface of the aluminum substrate."For more than two decades we've asked ourselves if the chemistry we find in space can make the kinds of compounds essential to life. So far, we haven't picked a single broad set of molecules that can't be produced," said Scott Sandford, a senior scientist in the Ames astrochemistry lab and an author on the new paper."The universe is an organic chemist," said Sandford. "It has big beakers and lots of time - and the result is a lot of organic material, some of which is useful to life."The scientists then went looking for those sugar compounds in samples from carbonaceous meteorites. While they didn't find 2-deoxyribose in their samples, they did find other sugars, meaning that with a large sample size, they could find the elusive key ingredient for life.The find only further encourages the theory that life on Earth either got help from an interstellar object plummeting down to the planet, delivering some key chemicals, or was transported wholesale from another world, blasted off by an impact and then unwittingly winding up here.In late October, a trio of Harvard scientists - including one who's attracted no shortage of ire as of late for suggesting the interstellar object 'Oumuamua might be a spacecraft - published a paper describing how life might have been transplanted here by a process called panspermia, even across interstellar distances.The basic idea of panspermia is that an impactor, like a comet or asteroid, crashes into world where life exists, blasting pieces of rock into space that carry the microbes and organic material to some other planet, where they eventually crash down when their rock becomes a meteor. If they survive, the microbes colonize the new world.While it's somewhat accepted that panspermia could transplant life from, say, Mars to Earth, life traveling longer distances across the unprotected interstellar medium seems less likely. Ames scientists took issue with the Harvard scientists' suggestion, criticizing it as improbable that the process could work between solar systems."If the journey took millions of years, then that life would die, and it doesn't matter if it is Earth life or non-Earth life," Rocco Mancinelli, a senior research scientist at the Ames Research Center, told NBC at the time. "Why? Because it would be destroyed by cosmic radiation. And even if it could survive that, the radiation given off by the mineral in the rock itself would destroy it."Meanwhile, the US space agency's OSIRIS-REx [Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer] spacecraft just arrived at the asteroid Bennu earlier this month, an odd rock that NASA scientists think might give them an idea of what the conditions of early Earth were like. OSIRIS-REx will collect samples from Bennu's surface and ship them to Earth after measuring the asteroid to see if it poses a threat to the planet. NASA's Jet Propulsion Laboratory gives the 110-mile-wide asteroid a cumulative 1-in-2,700 chance of impacting Earth between the years 2175 and 2199.On December 10, NASA announced OSIRIS-REx had found evidence of water clay on Bennu."Data obtained from the spacecraft's two spectrometers... reveal the presence of molecules that contain oxygen and hydrogen atoms bonded together, known as 'hydroxyls,'" the space agency said in a press release, Sputnik reported. "The [NASA] team suspects that these hydroxyl groups exist globally across the asteroid in water-bearing clay minerals, meaning that at some point, Bennu's rocky material interacted with water."Source: Sputnik News
  • Narrowing the universe in the search for life
    Montag, 07.01.2019, 05:59:02 Uhr
    Narrowing the universe in the search for life Columbus OH (SPX) Dec 18, 2018 -
    Humankind's exploration of space has for years pondered one central question: Is there another world somewhere in the universe where human beings could survive?And as astrophysicists and astronomers have searched for the answer, they've traditionally looked for a world that has water.But Wendy Panero, professor of earth sciences at The Ohio State University, has developed a new way of thinking about a planet's habitability. What if, she wondered, the answer to habitability lies within the way rocks and water interact?Panero presented her theory Dec. 12 at the fall meeting of the American Geophysical Union in Washington, D.C."We have traditionally looked for 'water worlds'--places where one-half to one-quarter of the weight of the planet is water," Panero said. "That seems like an optimal thing, to go looking for water."Instead of just looking for water, Panero thinks, scientists should also look to the planet's atmosphere.The Earth's atmosphere is stable and habitable in part because of carbon dioxide released when large tectonic plates under the Earth's crust shift and because of the weathering of rocks at the surface."You need something that allows volcanic rock to come back to the surface," Panero said. "It's a cycle."Panero thinks the Earth's near-constant sea level over geologic time is based on the way water at the planet's surface interacts with shifting plates. The Earth's interior provides energy that powers the dynamics of plate tectonics, which in turn has kept the amount of water cycling between the surface and its atmosphere stable for eons. The weathering and erosion of silicate rock helps regulate carbon dioxide levels in the atmosphere, and is a key part of the process.And though astrophysicists have traditionally searched for a world with water in the hopes of finding a world that can support life, Panero thinks there might be a way to evaluate the stuff of which a planet is made to determine if it could be habitable. The theory she presented Wednesday includes evaluating a planet's mass and radius, along with the composition of its star, which can be used to make predictions about the planet's interior and structure. In a universe of seemingly infinite planets, the theory could help narrow the field of planets that scientists look to for signs of life.That could help save both time and money in the search for extraterrestrial life."It's a way of cutting down your sample set of where you're going to spend your expensive space telescope time," Panero said.
  • A young star caught forming like a planet
    Montag, 07.01.2019, 05:59:02 Uhr
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    A young star caught forming like a planet Leeds UK (SPX) Dec 17, 2018 -
    Astronomers have captured one of the most detailed views of a young star taken to date, and revealed an unexpected companion in orbit around it.While observing the young star, astronomers led by Dr. John Ilee from the University of Leeds discovered it was not in fact one star, but two.The main object, referred to as MM 1a, is a young massive star surrounded by a rotating disk of gas and dust that was the focus of the scientists' original investigation.A faint object, MM 1b, was detected just beyond the disk in orbit around MM 1a. The team believe this is one of the first examples of a "fragmented" disk to be detected around a massive young star."Stars form within large clouds of gas and dust in interstellar space," said Dr. Ilee, from the School of Physics and Astronomy at Leeds."When these clouds collapse under gravity, they begin to rotate faster, forming a disk around them. In low mass stars like our Sun, it is in these disks that planets can form.""In this case, the star and disk we have observed is so massive that, rather than witnessing a planet forming in the disk, we are seeing another star being born."By measuring the amount of radiation emitted by the dust, and subtle shifts in the frequency of light emitted by the gas, the researchers were able to calculate the mass of MM 1a and MM 1b.Their work, published in the Astrophysical Journal Letters, found MM 1a weighs 40 times the mass of our Sun. The smaller orbiting star MM 1b was calculated to weigh less than half the mass of our Sun."Many older massive stars are found with nearby companions," added Dr. Ilee. "But binary stars are often very equal in mass, and so likely formed together as siblings. Finding a young binary system with a mass ratio of 80:1 is very unusual, and suggests an entirely different formation process for both objects."The favored formation process for MM 1b occurs in the outer regions of cold, massive disks. These "gravitationally unstable" disks are unable to hold themselves up against the pull of their own gravity, collapsing into one - or more - fragments.Dr. Duncan Forgan, a co-author from the Centre for Exoplanet Science at the University of St. Andrews, added: "I've spent most of my career simulating this process to form giant planets around stars like our Sun. To actually see it forming something as large as a star is really exciting."The researchers note that newly-discovered young star MM 1b could also be surrounded by its own circumstellar disk, which may have the potential to form planets of its own - but it will need to be quick.Dr. Ilee added: "Stars as massive as MM 1a only live for around a million years before exploding as powerful supernovae, so while MM 1b may have the potential to form its own planetary system in the future, it won't be around for long."The astronomers made this surprising discovery by using a unique new instrument situated high in the Chilean desert - the Atacama Large Millimeter/submillimeter Array (ALMA).Using the 66 individual dishes of ALMA together in a process called interferometry, the astronomers were able to simulate the power of a single telescope nearly 4 km across, allowing them to image the material surrounding the young stars for the first time.The team have been granted additional observing time with ALMA to further characterize these exciting stellar systems in 2019. The upcoming observations will simulate a telescope that is 16 km across - comparable to the area inside of the ring-road surrounding Leeds.Research Report: "G11.92-0.61 MM1: A Fragmented Keplerian Disk Surrounding a Proto-O Star," J. D. Ilee et al., 2018 Dec. 14, Astrophysical Journal Letters
  • Planets with Oxygen Don't Necessarily Have Life
    Montag, 07.01.2019, 05:59:02 Uhr
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    Planets with Oxygen Don't Necessarily Have Life Baltimore MD (SPX) Dec 18, 2018 -
    In their search for life in solar systems near and far, researchers have often accepted the presence of oxygen in a planet's atmosphere as the surest sign that life may be present there. A new Johns Hopkins study, however, recommends a reconsideration of that rule of thumb.Simulating in the lab the atmospheres of planets beyond the solar system, researchers successfully created both organic compounds and oxygen, absent of life.The findings, published Dec. 11 by the journal ACS Earth and Space Chemistry, serve as a cautionary tale for researchers who suggest the presence of oxygen and organics on distant worlds is evidence of life there."Our experiments produced oxygen and organic molecules that could serve as the building blocks of life in the lab, proving that the presence of both doesn't definitively indicate life," says Chao He, assistant research scientist in the Johns Hopkins University Department of Earth and Planetary Sciences and the study's first author. "Researchers need to more carefully consider how these molecules are produced."Oxygen makes up 20 percent of Earth's atmosphere and is considered one of the most robust biosignature gases in Earth's atmosphere. In the search for life beyond Earth's solar system, however, little is known about how different energy sources initiate chemical reactions and how those reactions can create biosignatures like oxygen.While other researchers have run photochemical models on computers to predict what exoplanet atmospheres might be able to create, no such simulations to He's knowledge have before now been conducted in the lab.The research team performed the simulation experiments in a specially designed Planetary HAZE (PHAZER) chamber in the lab of Sarah Horst, assistant professor of Earth and planetary sciences and the paper's co-author.The researchers tested nine different gas mixtures, consistent with predictions for super-Earth and mini-Neptune type exoplanet atmospheres; such exoplanets are the most abundant type of planet in our Milky Way galaxy. Each mixture had a specific composition of gases such as carbon dioxide, water, ammonia, and methane, and each was heated at temperatures ranging from about 80 to 700 degrees Fahrenheit.He and the team allowed each gas mixture to flow into the PHAZER setup and then exposed the mixture to one of two types of energy, meant to mimic energy that triggers chemical reactions in planetary atmospheres: plasma from an alternating current glow discharge or light from an ultraviolet lamp.Plasma, an energy source stronger than UV light, can simulate electrical activities like lightning and/or energetic particles, and UV light is the main driver of chemical reactions in planetary atmospheres such as those on Earth, Saturn and Pluto.After running the experiments continuously for three days, corresponding to the amount of time gas would be exposed to energy sources in space, the researchers measured and identified resulting gasses with a mass spectrometer, an instrument that sorts chemical substances by their mass to charge ratio.The research team found multiple scenarios that produced both oxygen and organic molecules that could build sugars and amino acids - raw materials for which life could begin - such as formaldehyde and hydrogen cyanide."People used to suggest that oxygen and organics being present together indicates life, but we produced them abiotically in multiple simulations," He says. "This suggests that even the co-presence of commonly accepted biosignatures could be a false positive for life.""Gas Phase Chemistry of Cool Exoplanet Atmospheres: Insight from Laboratory Simulations," Chao He, Sarah M. Horst et al., 2018 Nov. 26, ACS Earth and Space Chemistry
  • Where Did the Hot Neptunes Go - embargo 10am US Eastern Standard Time
    Montag, 07.01.2019, 05:59:02 Uhr
    Where Did the Hot Neptunes Go - embargo 10am US Eastern Standard Time Geneva, Switzerland (SPX) Dec 17, 2018 -
    "But where did the hot Neptunes go?" This is the question astronomers have been asking for a long time, faced with the mysterious absence of planets the size of Neptunes very close to their star. A team of researchers, led by astronomers from the University of Geneva (UNIGE), Switzerland, has just discovered that one of these planets is losing its atmosphere at a frantic pace.This observation strengthens the theory that hot Neptunes have lost much of their atmosphere and turned into smaller planets called super-Earths, which are much more numerous. Results to read in the journal Astronomy and Astrophysics.Fishermen would be puzzled if they netted only big and little fish, but few medium-sized fish. This is similar to what happens to astronomers hunting exoplanets. They found a large number of hot planets the size of Jupiter and numerous others a little larger than Earth (called super-Earths whose diameter does not exceed 1.5 times that of Earth), but no planets close to their star the size of Neptune. This mysterious "desert" of hot Neptunes suggests two explanations: either such alien worlds are rare, or, they were plentiful at one time, but have since disappeared.A few years ago, UNIGE astronomers using NASA's Hubble Space Telescope discovered that a warm Neptune on the edge of the desert, GJ 436b, was losing hydrogen from its atmosphere. This loss is not enough to threaten the atmosphere of GJ 436b, but suggested that Neptunes receiving more energy from their star could evolve more dramatically. This has just been confirmed by the same astronomers, members of the national research center PlanetS[1].They observed with Hubble that another warm Neptune at the edge of the desert, named GJ 3470b, is losing its hydrogen 100 times faster than GJ 436b. The two planets reside about 3.7 million kilometers from their star, one-tenth the distance between Mercury and the Sun, but the star hosting GJ 3470b is much younger and energetic."This is the first time that a planet has been observed to lose its atmosphere so quickly that it can impact its evolution," says Vincent Bourrier, researcher in the Astronomy Department of the Faculty of Science of the UNIGE, member of the European project FOUR ACES[2] and first author of the study. The team estimates that GJ 3470b has already lost more than a third of its mass."Until now we were not sure of the role played by the evaporation of atmospheres in the formation of the desert," states Vincent Bourrier. The discovery of several warm Neptunes at the edge of the desert losing their atmosphere supports the idea that the hotter version of these planets is short-lived.Hot Neptunes would have shrunk to become mini-Neptunes, or would have eroded completely to leave only their rocky core. "This could explain the abundance of hot super-Earths that have been discovered," says David Ehrenreich, associate professor in the astronomy department of the science faculty at UNIGE and co-author of the study.The Evolution of the Hot Neptune Hunt
    Observing the evaporation of two warm Neptunes is encouraging, but team members know they need to study more of them to confirm their predictions. Unfortunately, the hydrogen that escapes from these planets cannot be detected if they are more than 150 light-years from Earth (GJ 3470b is 97 light-years away), because hydrogen is then hidden by interstellar gas.Researchers thus plan to use Hubble to look for other traces of atmospheric escape, because hydrogen could drag upward heavier elements such as carbon. The solution could also come from helium, whose infrared radiation isn't blocked by interstellar medium."Helium will expand the range of our surveys," said Vincent Bourrier, "the high sensitivity of the James Webb space telescope should allow us to detect helium escaping small planets, such as mini-Neptunes, and complete our observations of the edge of the desert."Research Report: [1] PlanetS is a National Research Centre, a research instrument of the Swiss National Science Foundation dedicated to research on exoplanets.[2] FOUR ACES, Future of Upper Atmospheric Characterization of Exoplanets with Spectroscopy, is a project funded by a European Research Council (ERC) Consolidator Grant under the European Commission's Research and Innovation Program Horizon 2020 (Grant No 724427).
  • In search of missing worlds, Hubble finds a fast-evaporating exoplanet
    Montag, 07.01.2019, 05:59:02 Uhr
    In search of missing worlds, Hubble finds a fast-evaporating exoplanet Baltimore MD (SPX) Dec 17, 2018 -
    Fishermen would be puzzled if they netted only big and little fish, but few medium-sized fish. Astronomers likewise have been perplexed in conducting a census of star-hugging extrasolar planets. They have found hot Jupiter-sized planets and hot super-Earths (planets no more than 1.5 times Earth's diameter). These planets are scorching hot because they orbit very close to their star. But so-called "hot Neptunes," whose atmospheres are heated to more than 1,700 degrees Fahrenheit, have been much harder to find. In fact, only about a handful of hot Neptunes have been found so far.In fact, most of the known Neptune-sized exoplanets are merely "warm," because they orbit farther away from their star than those in the region where astronomers would expect to find hot Neptunes. The mysterious hot-Neptune deficit suggests that such alien worlds are rare, or, they were plentiful at one time, but have since disappeared.A few years ago astronomers using NASA's Hubble Space Telescope (http://www.nasa.gov/hubble) found that one of the warmest known Neptunes (GJ 436b) is losing its atmosphere. The planet isn't expected to evaporate away, but hotter Neptunes might not have been so lucky.Now, astronomers have used Hubble to nab a second "very warm" Neptune (GJ 3470b) that is losing its atmosphere at a rate 100 times faster than that of GJ 436b. Both planets reside about 3.7 million miles from their star. That's one-tenth the distance between our solar system's innermost planet, Mercury, and the Sun."I think this is the first case where this is so dramatic in terms of planetary evolution," said lead researcher Vincent Bourrier of the University of Geneva in Sauverny, Switzerland. "It's one of the most extreme examples of a planet undergoing a major mass loss over its lifetime. This sizable mass loss has major consequences for its evolution, and it impacts our understanding of the origin and fate of the population of exoplanets close to their stars."As with the previously discovered evaporating planets, the star's intense radiation heats the atmosphere to a point where it escapes the planet's gravitational pull like an untethered hot air balloon. The escaping gas forms a giant cloud around the planet that dissipates into space. One reason why GJ 3470b may be evaporating faster than GJ 436b is that it is not as dense, so it is less able to gravitationally hang on to the heated atmosphere.What's more, the star hosting GJ 3470b is only 2 billion years old, compared to the 4-billion- to 8-billion-year-old star that planet GJ 436b orbits. The younger star is more energetic, so it bombards the planet with more blistering radiation than GJ 436b receives. Both are red dwarf stars, which are smaller and longer-lived than our Sun.Uncovering two evaporating warm Neptunes reinforces the idea that the hotter version of these distant worlds may be a class of transitory planet whose ultimate fate is to shrink down to the most common type of known exoplanet, mini-Neptunes - planets with heavy, hydrogen-dominated atmospheres that are larger than Earth but smaller than Neptune. Eventually, these planets may downsize even further to become super-Earths, more massive, rocky versions of Earth."The question has been, where have the hot Neptunes gone?" said Bourrier. "If we plot planetary size and distance from the star, there's a desert, a hole, in that distribution. That's been a puzzle. We don't really know how much the evaporation of the atmospheres played in forming this desert. But our Hubble observations, which show a large amount of mass loss from a warm Neptune at the edge of the desert, is a direct confirmation that atmospheric escape plays a major role in forming this desert."The researchers used Hubble's Space Telescope Imaging Spectrograph to detect the ultraviolet-light signature of hydrogen in a huge cocoon surrounding the planet as it passed in front of its star. The intervening cocoon of hydrogen filters out some of the starlight. These results are interpreted as evidence of the planet's atmosphere bleeding off into space.The team estimates that the planet has lost as much as 35 percent of its material over its lifetime, because it was probably losing mass at a faster rate when its red-dwarf star was younger and emitting even more radiation. If the planet continues to rapidly lose material, it will shrink down to a mini-Neptune in a few billion years.Hydrogen probably isn't the only element evaporating away: it may be a tracer for other material streaming off into space. The researchers plan to use Hubble to hunt for elements heavier than hydrogen and helium that have hitched a ride with the hydrogen gas to escape the planet. "We think that the hydrogen gas could be dragging heavy elements such as carbon, which reside deeper in the atmosphere, upward and out into space." Bourrier said.The observations are part of the Panchromatic Comparative Exoplanet Treasury (PanCET) survey, a Hubble program to look at 20 exoplanets, mostly hot Jupiters, in the first large-scale ultraviolet, visible, and infrared comparative study of distant worlds.Observing the evaporation of these two warm Neptunes is encouraging, but team members know they need to study more of them to confirm predictions. Unfortunately, there may be no other planets of this class residing close enough to Earth to observe. The problem is that hydrogen gas cannot be detected in warm Neptunes farther away than 150 light-years from Earth because it is obscured by interstellar gas. GJ 3470b resides 97 light-years away.However, helium is another tracer for material escaping a warm Neptune's atmosphere. Astronomers could use Hubble and the upcoming NASA James Webb Space Telescope to search in infrared light for helium, because it is not blocked by interstellar material in space."Looking for helium could expand our survey range," Bourrier said. "Webb will have incredible sensitivity, so we would be able to detect helium escaping from smaller planets, such as mini-Neptunes."
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