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  • richardmitnick 8:13 am on April 22, 2020 Permalink | Reply
    Tags: , , , , , Science Alert   

    From Science Alert: “The Composition of Interstellar Comet 2I/Borisov Is Much More Alien Than We Thought” 

    ScienceAlert

    From Science Alert

    22 APRIL 2020
    MICHELLE STARR

    1
    Artist’s impression of 2I/Borisov. (NRAO/AUI/NSF, S. Dagnello)

    When the first known comet from interstellar space was spotted traversing the Solar System in late August of last year, astronomers snapped to attention. 2I/Borisov was an extraordinarily rare opportunity to study the formation of comets around other stars.

    In those initial measurements, 2I/Borisov seemed a heck of a lot like comets from the outer Solar System. But a new analysis has revealed that our visitor is much more alien than we thought after all.

    In the cloud of gas that the comet started to emit as it neared the Sun, a team of astronomers detected more carbon monoxide than they’ve ever seen in a comet within 300 million kilometres (180 million miles) of the Sun.

    “This is the first time we’ve ever looked inside a comet from outside our Solar System,” said astrochemist Martin Cordiner of the Catholic University of America, “and it is dramatically different from most other comets we’ve seen before.”

    2I/Borisov wasn’t the first known interstellar object in the Solar System; that was ‘Oumuamua, whose identity is still uncertain. However, 2I/Borisov is the first known comet, which made it very exciting indeed.

    Comets spend most of their time in the cold outer reaches of a planetary system; at least, that’s our experience with the Solar System.

    Short-period comets formed in the Kuiper Belt, the debris field where Pluto lives, which astronomers believe formed much closer to the Sun and migrated outwards, while long-period comets formed in the Oort Cloud, which is wayyyyy out farther still (but probably formed closer to the Sun than the Kuiper Belt).

    As a consequence, comets are like time capsules, changing very little from the time they were formed. It’s therefore thought that these peregrinating chunks of rock and ice can tell us a lot about the composition and processes of early planetary systems.

    We don’t know much about how this happens in other planetary systems, but we’re dying to find out – not least because comets raining down on early Earth could have been a major ingredient in kickstarting life, carrying water and other ingredients necessary for the process.

    So, as 2I/Borisov sped away from the Sun after its December 8 perihelion, astronomers made a careful study of its coma, the cloud of gas that envelops a comet as it nears the Sun, and the ice inside sublimates due to the heat.

    They used the Atacama Large Millimeter/submillimeter Array in Chile to obtain detailed spectra and images of the comet as it journeyed through the inner Solar System. These break down the wavelengths of the light bouncing off the comet, which allows scientists to look for wavelengths absorbed or emitted by specific molecules.

    2I/Borisov’s coma contained hydrogen cyanide; this is fairly typical for Solar System comets, and 2I/Borisov was emitting it in normal amounts. But the CO levels made the team do a double take.

    Although most Solar System comets do contain CO, in wildly varying amounts, 2I/Borisov had way more than we usually see – between 9 and 26 times more than the average Solar System comet, the researchers said.

    Astronomers aren’t sure why Solar System comets have such varying proportions of CO, but they think it may have to do with the temperature at which the comet formed. The colder the temperature, the greater the concentration of CO. This means, the researchers believe, that 2I/Borisov formed somewhere very cold indeed.

    “The comet must have formed from material very rich in CO ice, which is only present at the lowest temperatures found in space, below -420 degrees Fahrenheit (-250 degrees Celsius),” said planetary scientist Stefanie Milam of NASA.

    This region around another star would be analogous to the current distance of the Kuiper Belt – but, because the rocks in the Kuiper Belt are thought to have formed closer to the Sun, the CO levels in its comets are much lower than if they formed at the current distance.

    That means 2I/Borisov doesn’t really fit with the comet formation models we’ve based on the Solar System. It’s possible that it’s a chunk of CO-rich dwarf planet. Or it could have an insulating layer that keeps other volatiles frozen while CO sublimates.

    It defies easy explanation, but 2I/Borisov has reached the end of the line in the Solar System, and has been observed breaking into pieces. This could tell us a lot about the interior composition of the comet, and help rule out or confirm the team’s hypotheses.

    But high cometary CO levels aren’t without precedent, either. A comet discovered in 2016 – C/2016 R2 (PanSTARRS) – was found to have CO levels dozens of times higher than 2I/Borisov’s.

    This was interpreted as an origin in the Oort Cloud, but 2I/Borisov raises the possibility that C/2016 R2 (PanSTARRS) could have had an interstellar origin too. That’s a really intriguing idea, but we may be waiting a while for answers.

    “2I/Borisov gave us the first glimpse into the chemistry that shaped another planetary system,” Milam said. “But only when we can compare the object to other interstellar comets, will we learn whether 2I/Borisov is a special case, or if every interstellar object has unusually high levels of CO.”

    The research has been published in Nature Astronomy.

    See the full article here .


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  • richardmitnick 9:29 am on April 20, 2020 Permalink | Reply
    Tags: "Astronomers Find a Beautiful Six-Planet System in Almost Perfect Orbital Harmony", , , , , Science Alert, Star HD 158259   

    From University of Geneva: “Astronomers Find a Beautiful Six-Planet System in Almost Perfect Orbital Harmony” 


    20 APRIL 2020
    MICHELLE STARR

    1
    Artist’s impression of six planets orbiting Sun-like star Kepler-11. (NASA/Tim Pyle)

    By now, we have discovered hundreds of stars with multiple planets orbiting them scattered throughout the galaxy. Each one is unique, but a system orbiting the star HD 158259, 88 light-years away, is truly special.

    The star itself is about the same mass and a little larger than the Sun – a minority in our exoplanet hunts. It’s orbited by six planets: a super-Earth and five mini-Neptunes.

    After monitoring it for seven years, astronomers have discovered that all six of those planets are orbiting HD 158259 in almost perfect orbital resonance. This discovery could help us to better understand the mechanisms of planetary system formation, and how they end up in the configurations we see.

    Orbital resonance is when the orbits of two bodies around their parent body are closely linked, as the two orbiting bodies exert gravitational influence on each other. In the Solar System, it’s pretty rare in planetary bodies; probably the best example is Pluto and Neptune.

    These two bodies are in what is described as a 2:3 orbital resonance. For every two laps Pluto makes around the Sun, Neptune makes three. It’s like bars of music being played simultaneously, but with different time signatures – two beats for the first, three for the second.

    Orbital resonances have also been identified in exoplanets. But each planet orbiting HD 158259 is in an almost 3:2 resonance with the next planet out away from the star, also described as a period ratio of 1.5. That means for every three orbits each planet makes, the next one out completes two.

    Using measurements taken using the SOPHIE spectrograph and the TESS exoplanet-hunting space telescope, an international team of researchers led by astronomer Nathan Hara of the University of Geneva in Switzerland were able to precisely calculate the orbits of each planet.

    1
    SOPHIE spectrograph installed on the 1.93m reflector telescope at the Haute-Provence Observatory located in south-eastern France.

    Haute-Provence Observatory 1.93 meter telescope interior

    NASA/MIT TESS replaced Kepler in search for exoplanets

    They’re all very tight. Starting closest to the star – the super-Earth, revealed by TESS to be around twice the mass of Earth – the orbits are 2.17, 3.4, 5.2, 7.9, 12, and 17.4 days.

    These produce period ratios of 1.57, 1.51, 1.53, 1.51, and 1.44 between each pair of planets. That’s not quite perfect resonance – but it’s close enough to classify HD 158259 as an extraordinary system.

    And this, the researchers believe, is a sign that the planets orbiting the star did not form where they are now.

    “Several compact systems with several planets in, or close to, resonances are known, such as TRAPPIST-1 or Kepler-80,” explained astronomer Stephane Udry of the University of Geneva.

    “Such systems are believed to form far from the star before migrating towards it. In this scenario, the resonances play a crucial part.”

    That’s because these resonances are thought to result when planetary embryos in the protoplanetary disc grow and migrate inwards, away from the outer edge of the disc. This produces a chain of orbital resonance throughout the system.

    Then, once the remaining gas of the disc dissipates, this can destabilise the orbital resonances – and this could be what we’re seeing with HD 158259. And those tiny differences in the orbital resonances could tell us more about how this destabilisation is occurring.

    “The current departure of the period ratios from 3:2 contains a wealth of information,” Hara said.

    “With these values on the one hand, and tidal effect models on the other hand, we could constrain the internal structure of the planets in a future study. In summary, the current state of the system gives us a window on its formation.”

    The research has been published in Astronomy & Astrophysics.

    See the full article here.

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    The University of Geneva (French: Université de Genève) is a public research university located in Geneva, Switzerland.

    It was founded in 1559 by John Calvin as a theological seminary and law school. It remained focused on theology until the 17th century, when it became a center for Enlightenment scholarship. In 1873, it dropped its religious affiliations and became officially secular. Today, the university is the third largest university in Switzerland by number of students. In 2009, the University of Geneva celebrated the 450th anniversary of its founding. Almost 40% of the students come from foreign countries.

    The university holds and actively pursues teaching, research, and community service as its primary objectives. In 2016, it was ranked 53rd worldwide by the Shanghai Academic Ranking of World Universities, 89th by the QS World University Rankings, and 131st in the TIMES Higher Education World University Ranking.

    UNIGE is a member of the League of European Research Universities (including academic institutions such as Amsterdam, Cambridge, Heidelberg, Helsinki and Milan) the Coimbra Group and the European University Association.

     
  • richardmitnick 10:09 am on April 16, 2020 Permalink | Reply
    Tags: "Exclusive: How Scientists in Antarctica Are Living Untouched by The Global Pandemic", "It's a worrying time for all of us here in Antarctica-We don't have much of a true idea of what life is like back home., "The consequences of an outbreak on station would be devastating when you consider we only have one doctor and a well-equipped but small medical suite.", As the COVID-19 pandemic spreads around the world there are few places where the virus itself hasn't been able to reach., In winter these bases house approximately 1000 people and in summer this number swells to more than 4000., Science Alert, Thankfully the station also has two years of food stocks in case anything was to go wrong and a lot of free time on their hands., There are around 70 active Antarctic bases spread across an icy continent the size of the US and Mexico combined.   

    From Science Alert: “Exclusive: How Scientists in Antarctica Are Living Untouched by The Global Pandemic” 

    ScienceAlert

    From Science Alert

    16 APRIL 2020
    JACINTA BOWLER

    1
    Last year’s final sunset at Davis Station. (Glenn Smith/Australian Antarctic Division)

    On the frigid landscape of Antarctica’s Ingrid Christensen Coast sits Davis Station, where 24 people are hunkered down for a long and dark winter.

    Although this happens every year, with the winter crew taking atmospheric observations, fixing seabird cameras, and looking after the station while the Sun slowly sets, this year things feel different.

    “It’s a worrying time for all of us here in Antarctica,” Davis Station leader David Knoff told ScienceAlert in an email.

    “We don’t have much of a true idea of what life is like back home.”

    As the COVID-19 pandemic spreads around the world, there are few places where the virus itself hasn’t been able to reach.

    Even hundreds of kilometres above Earth, COVID-19 has been keeping the International Space Station (ISS) crew on their toes. Just last week, Expedition 63 members travelled on the Soyuz rocket to the station, after weeks of the astronauts undergoing quarantine, and tight restrictions on the launch.

    “I knew I was going to be in quarantine these two weeks, but what’s really different is everybody else around us is in quarantine, too,” American astronaut Chris Cassidy said in a prelaunch interview on NASA TV.

    “It’ll be a really, really skeletal crew in the Baikonur Cosmodrome, which will be quite different.”

    Meanwhile at Davis Station, the last of the summer team left Antarctica in mid-February – when the worldwide effect of COVID-19 was just becoming apparent.

    “No one had ever heard of COVID-19 when we left Australia back in October, but it started to have an impact on the Australian Antarctic Program as far back as early January,” Knoff explains.

    “The consequences of an outbreak on station would be devastating when you consider we only have one doctor and a well-equipped but small medical suite.”

    There are around 70 active Antarctic bases spread across an icy continent the size of the US and Mexico combined. In winter, these bases house approximately 1,000 people, and in summer this number swells to more than 4,000.

    The Australian Antarctic Division currently has 89 winter crew members across its four stations. The team has been well prepared for a long, cold winter where the Sun eventually doesn’t rise at all for a couple of weeks, but hunkering down during a global pandemic casts a new light on the experience.

    “It’s definitely made being away from home a little more challenging,” says Knoff.

    “Ordinarily everyone would be happily getting on with their lives back home, but now with COVID-19 people are losing jobs, being forced to stay home and not travel, worrying about loved ones getting sick or having to dramatically alter their lifestyles to stay safe.”

    The 24 Australians and New Zealanders on Davis Station are keeping positive. They have huge stocks of movies, Tim Tam biscuits, and a WiFi connection. Not to mention the elephant seals and penguins just outside their doorstep.

    “The first thing I’d do when I return is see my family and friends, which right now would be one-on-one or via Skype so for now I might as well just stay here,” says Knoff.

    But, just like on the mainland, the havoc caused by COVID-19 on research likely hasn’t yet been truly felt.

    “The impact of COVID-19 on the scientific research down here will probably be felt most heavily next summer,” Dan Dyer, senior winter scientist at Davis, told ScienceAlert.

    “While nothing’s final yet, it’s likely that a number of the science projects which were planned for next summer will have to be postponed or scaled back as it may not be possible to send down some of the scientists and their equipment who were originally scheduled to be here next summer.”

    Each summer, all types of scientists make the trek to the frozen continent. They undertake population counts of penguins and seabirds, collect data from seismometers and GPS stations, run a neutrino-hunting experiment, and maintain atmospheric observatories important for weather modelling and climate change research.

    “It’s always sad to see years of hard work affected by events like this which are completely outside anyone’s control,” Dyer adds.

    For the winter crew it’s still early days. The team at Davis still have months until the originally scheduled date for travelling back to Australia. Thankfully, the station also has two years of food stocks in case anything was to go wrong, and a lot of free time on their hands.

    “There is a well-stocked library, a station band, a cinema, cross country skis, a running track (for the brave) and a good gym complete with sauna and spa to warm up after a run,” says Knoff.

    But as protected as they are in their winter haven, the global presence of COVID-19 has caused some uncertainty even so far from the disease.

    “At this stage we are due to return to Australia sometime during next summer. There are of course some unknowns in the months ahead regarding international travel, shipping and aviation which may have an impact,” Knoff adds.

    “Hopefully, see you all next summer…”

    See the full article here .


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  • richardmitnick 8:29 am on April 13, 2020 Permalink | Reply
    Tags: "Lose Yourself in a Breathtaking New NASA Image of The 'Pillars of Creation'", , , , , , Science Alert   

    From Science Alert: “Lose Yourself in a Breathtaking New NASA Image of The ‘Pillars of Creation'” 

    ScienceAlert

    From Science Alert

    13 APRIL 2020
    VICTOR TANGERMANN

    1
    (NASA, ESA/Hubble and the Hubble Heritage Team)

    NASA and ESA’s incredible view of the ‘Pillars of Creation’, courtesy of the Hubble Space Telescope, has become one of the most iconic views of our cosmos since it was first captured in 1995.

    The agencies’ newest image of the structure in the Eagle Nebula, however, has left us speechless.

    It shows the radiating glow of the pillars in infrared light – and you can see the infrared light piercing through dust and gas, giving the pillars a spectacular blueish shadow.

    2
    (NASA, ESA/Hubble and the Hubble Heritage Team)

    The 1995 image of the pillars, a composite of three different images compiled using visible light, shows the pillars located in the Eagle Nebula throwing off cool hydrogen gas and cosmic dust.

    3
    The 1995 image of the pillars. (NASA, ESA, STScI, J. Hester and P. Scowen (Arizona State University))

    The new infrared version is not the first time images of this cosmic structure have been revisited. In 2015, astronomers assembled a more detailed image captured in visible light.

    4
    (NASA, ESA/Hubble and the Hubble Heritage Team)

    First discovered in 1745 by Swiss astronomer Jean-Philippe Loys de Cheseaux, the Eagle Nebula is roughly 7,000 light-years from Earth, a nursery for stars in the Serpens constellation.

    At four to five light-years in width, the pillar structure is immense, although it’s just a relatively small structure compared to the overall nebula, which spans a staggering 70 by 55 light-years.

    See the full article here .


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  • richardmitnick 9:17 am on April 9, 2020 Permalink | Reply
    Tags: (LCRT)-Lunar Crater Radio Telescope, , Science Alert   

    From Science Alert: “NASA Reveals Wild Project For Turning a Moon Crater Into a Radio Telescope” 

    ScienceAlert

    From Science Alert

    1
    (Saptarshi Bandyopadhyay)

    9 APRIL 2020
    DAVID NIELD

    NASA just gave out a new round of grants for its favourite up and coming innovative space projects – one of which is a plan to fit a 1 kilometre (3,281 foot) radio telescope inside a crater on the far side of the Moon.

    The Lunar Crater Radio Telescope (LCRT) would be able to measure wavelengths and frequencies that can’t be detected from Earth, working unobstructed by the ionosphere or the various other bits of radio noise surrounding our planet.

    Should the plans for the LCRT become a reality – and the new grant money could get it closer to that – it would be the largest filled-aperture radio telescope in the Solar System.

    2
    How the LCRT might look. (Saptarshi Bandyopadhyay)

    “LCRT could enable tremendous scientific discoveries in the field of cosmology by observing the early universe in the 10–50m wavelength band (6–30MHz frequency band), which has not been explored by humans to date,” writes robotics technologist Saptarshi Bandyopadhyay of the NASA Jet Propulsion Laboratory (JPL) in his project outline.

    As per the plans, Moon rovers would pull out a wire mesh some 1 kilometre across, inside a lunar crater than could be up to 5 kilometres (3.1 miles) in diameter. A suspended receiver in the centre of the crater would complete the system.

    Everything could be automated without any human operators, which would in turn mean a lighter and less expensive payload for the project to literally get off the ground.

    This is still at the very early stage of planning, and it’s not clear yet exactly which crater would be used for the job, but it’s an intriguing concept that we’ll be keeping an eye on in the years ahead.

    The biggest radio telescope here on Earth is the Five-hundred metre Aperture Spherical Telescope or FAST, which has a 500 metre (1,640 foot) diameter.

    FAST [Five-hundred-meter Aperture Spherical Telescope] radio telescope, with phased arrays from CSIRO engineers Australia [located in the Dawodang depression in Pingtang County, Guizhou Province, south China

    Should the LCRT eventually get put together, it would be twice as wide.

    4
    The LCRT would be installed by rovers. (Saptarshi Bandyopadhyay)

    FAST is already proving its worth, having already picked up mysterious fast radio bursts or FRBs from the depths of space. The LCRT proposed here has the potential to pick up many more phenomena.

    There’s now such an abundance of low Earth orbit satellites, listening to the cosmos from the surface of our planet is becoming increasingly difficult.

    Working at low frequencies in the 6 to 30MHz frequency band, the lunar crater telescope could perhaps tell us more about the earliest days of the Universe.

    China and the Netherlands have already set up a radio telescope on the far side of the Moon, albeit a much smaller one. This telescope uses satellites to relay data back to Earth, like the LCRT will have to, if we pull it off.

    The team behind the concept now has nine months and up to US$125,000 of NASA money to see if they can develop it further. Let’s hope they’re successful.

    “Building the largest filled-aperture radio telescope in the Solar System on the far-side of the Moon is bound to create a lot of public excitement,” Bandyopadhyay and his colleagues write in a 2018 paper on the idea.

    “We envisage that this concept would unlock the potential for ground-breaking scientific discoveries in radio astronomy in wavelengths that are hitherto poorly explored by humans so far.”

    See the full article here .


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  • richardmitnick 10:05 am on March 30, 2020 Permalink | Reply
    Tags: , , NASA's DART (Double Asteroid Redirection Test) mission, NASA's Evolutionary Xenon Thruster – Commercial (NEXT-C), NEXT-C is a powerful engine. It's nothing like a rocket which requires a massive amount of thrust to lift something away from Earth's gravity., Science Alert, The Italian Space Agency is providing LICIA (Light Italian CubeSat for Imaging of Asteroids) for the mission., This Epic Ion Engine Will Power NASA's Test Mission to Redirect an Asteroid, Tiny binary asteroid system called Didymos   

    From Science Alert: “This Epic Ion Engine Will Power NASA’s Test Mission to Redirect an Asteroid” 

    ScienceAlert

    From Science Alert

    29 MARCH 2020
    EVAN GOUGH

    1
    (NASA/Bridget Caswell)

    Despite humanity’s current struggle against the novel coronavirus, and despite it taking up most of our attention, other threats still exist. The very real threat of a possible asteroid strike on Earth in the future is taking a backseat for now, but it’s still there.

    Though an asteroid strike seems kind of ephemeral right now, it’s a real threat, and one that has the potential to end humanity. Agencies like NASA and the ESA are still working on their plans to protect us from that threat.

    NASA’s DART (Double Asteroid Redirection Test) mission is scheduled to launch on 22 July 2021.

    NASA DART Double Impact Redirection Test vehicle depiction schematic

    It’s a demonstration mission to study the use of kinetic impact to deflect an asteroid. It’ll head for the tiny binary asteroid system called Didymos, (or 65803 Didymos.) This double asteroid system poses no threat to Earth.

    The larger of the pair, named Didymos A, is about 780 meters (2560 ft.) in diameter, while the smaller one, Didymos B, is only about 160 meters (535 feet) DART will crash itself into the Didymos B. It’s close to the typical size of an asteroid that threatens Earth.

    2
    A simulated image of the Didymos binary asteroid. (Naidu et al., AIDA Workshop, 2016)

    DART has a lot of space to cover to reach Didymos. After launching in July 2021, it will reach its target in September 22, when the binary asteroid is within 11 million km (6.8 million miles) of Earth. And to get there, it’ll rely on a powerful ion engine called NASA’s Evolutionary Xenon Thruster – Commercial (NEXT-C).

    The engine comes in two primary components: the thruster and the power processing unit (PPU.) NEXT-C is getting ready for the mission with a series of tests, both performance and environmental.

    The thruster was put through vibration, thermal vacuum and performance tests before being integrated with its PPU. It was also subjected to simulated spaceflight conditions: the extreme vibration during launch, and the extreme cold of space.

    3
    The power processing unit of the thruster is removed from another vacuum chamber after successful testing. (NASA/Bridget Caswell)

    NEXT-C is a powerful engine. It’s nothing like a rocket, which requires a massive amount of thrust to lift something away from Earth’s gravity. But in terms of ion drives, it’s a very powerful unit. It’s about three times more powerful than the NSTAR ion drives on NASA’s DAWN and Deep Space One spacecraft.

    NASA/DLR Dawn Spacecraft (2007-2018)

    3
    Deep Space One spacecraft. Wikipedia

    NEXT can produce 6.9 kW thrust power and 236 mN thrust. The engine has produced the highest total impulse of any ion engine: 17 MN·s. It also has a specific impulse, which is a measure of how efficiently it uses propellant, of 4,190 seconds, compared to NSTAR’s 3,120.

    Ion drives don’t burn fuel like a rocket, though they do use a propellant. Typically the propellant is xenon, like in NEXT-C. The NEXT-C ion engine is a double-grid system.

    The xenon is fed into a chamber, where it encounters the first, or upstream, grid. Solar arrays provide the electricity, and the first grid is charged positive. As the xenon ions pass through the upstream grid, they are charged positively.

    This draws them toward the second or accelerator grid, which is charged negatively. This propels them out of the engine, providing thrust. The thrust is equal to the force between the upstream ions and the accelerator grid.

    4
    NASA Evolutionary Xenon Thruster being tested in a vacuum chamber. (NASA)

    When DART reaches the Didymos binary asteroid, it will have some company. The Italian Space Agency is providing LICIA (Light Italian CubeSat for Imaging of Asteroids) for the mission.

    6
    https://www.nanosats.eu/sat/liciacube

    LICIA is 6 cubesats that will separate from DART prior to impact with Didymos B. It’ll capture images of the impact and the debris ejected from the collision and transmit it back to Earth.

    The impact is expected to change Didymos B’s orbital velocity by about a half millimeter per second. That will change its rotation period by a large enough amount that Earth-based telescopes will detect it. It will also leave a crater in the surface, about 20 m (66 ft) wide.

    Though DART will be destroyed when it impacts, the ESA is planning a follow-up mission. It’s called Hera, and it’s scheduled to launch in 2024, and to arrive in 2027.

    ESA’s proposed Hera spaceraft depiction

    Hera will investigate not only the effect of DART’s impact, but will carry a suite of instruments to learn more about binary asteroids, and the interior of the asteroid.

    See the full article here .


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  • richardmitnick 9:39 am on March 30, 2020 Permalink | Reply
    Tags: "Necroplanetology: The Strangest Field of Astronomy You've Never Heard Of", , , , , Science Alert, The star is called WD 1145+017   

    From Science Alert: “Necroplanetology: The Strangest Field of Astronomy You’ve Never Heard Of” 

    ScienceAlert

    From Science Alert

    28 MARCH 2020
    MICHELLE STARR

    1
    (NASA/JPL-Caltech)

    In 2015, astronomers found something weird. It was a white dwarf star, 570 light-years from Earth, with a peculiar dimming pattern. It dimmed several times to varying depths, each depth repeating on a 4.5 to 5-hour timeframe; and its atmosphere was polluted with elements usually found in rocky exoplanets.

    It didn’t take long before they figured it out. The gravity of the dead star was in the process of shredding and devouring bodies in orbit around it, a violent process known rather politely as tidal disruption.

    The star is called WD 1145+017, and it’s now being used as a proof of concept for a new field of planet study, forensic reconstruction of planetary bodies to understand what they were like, and how they died.

    Astronomers from the US and the UK are calling this field necroplanetology.

    Their analysis of WD 1145+017 has been accepted into The Astrophysical Journal, and is available on arXiv [https://arxiv.org/abs/2003.08410]. And it could, the researchers say, be applied to future discoveries similar to the white dwarf system to piece together how planets die orbiting different kinds of dead stars.

    Although white dwarfs eject a lot of material when they die in a series of violent thermonuclear explosions, planets can somehow survive the process. Not only have we found planets in orbit around white dwarf stars, we have found elements in the atmospheres of white dwarf stars that are usually found inside rocky exoplanets.

    The surface gravity of white dwarfs is so intense that these heavier elements would sink quite quickly, indicating that the star must have accreted the material quite recently, from a body that survived the star’s death throes.

    To try and determine how WD 1145+017 got the way it did, astronomers from the University of Colorado, Boulder, Wesleyan University, and the University of Warwick in the UK conducted a series of simulations to place constraints on the tidally disrupted body.

    They tweaked structural components of an orbiting body, such as the size of the core and mantle; the composition of the mantle, rocky or icy; and the presence of a crust. This resulted in 36 different simulated bodies.

    Then, they set each of these 36 bodies orbiting a star like WD 1145+017, around 60 percent of the mass of the Sun, and 2 percent of its size (white dwarfs are pretty dense).

    This orbit was 4.5 hours, as per the material orbiting WD 1145+017, and each simulation ran for 100 orbits. And finally, the resulting light curves for the tidal disruption of each body were then compared with the real-life light curve of WD 1145+017.

    These simulations showed that the bodies most likely to produce what we observe in WD 1145+017 have a small core, and a low-density mantle, “resembling an asteroid with a partially differentiated structure and volatile-rich mantle like Vesta,” the researchers wrote in their paper.

    The bodies are relatively low mass, and have bulk density high enough to maintain structure for a while, but low enough that their mantles are disrupted. These attributes are consistent with the lack of small particles found in other observations of the star, since these would sublimate quickly.

    And, in fact, they offer some clues as to other mysterious stars as well – such as the famous KIC 8462852, AKA Tabby’s star, whose inconsistent dimming is a source of much puzzlement among astronomers.

    KIC 8462852, since its strange behaviour was first discovered, has turned out not to be the only star exhibiting such strange dimming. A survey last year turned up another 21 strangely dimming stars that could have similar dynamics.

    And other white dwarfs slurping down orbiting bodies have been discovered, too. ZTF J0139+5245 and WD J0914+1914 were both discovered tidally disrupting planets last year.

    These stars could be simulated using the team’s new methods, too.

    “These are the first members of a larger class of dying planetary systems that must be studied by pairing spectroscopic and photometric observations with disruption simulations, either tidal as in WD 1145+017 or rotational as Veras et al. (2020) proposes for the body transiting ZTF J0139+5245,” the researchers wrote in their paper.

    “This multi-pronged approach would use the death of these planetary systems in action to study fundamental properties of exoplanetary bodies that are otherwise inaccessible: a study in necroplanetology.”

    See the full article here .


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  • richardmitnick 11:01 am on March 25, 2020 Permalink | Reply
    Tags: , , , Chaos in the Universe is a feature not a bug., , It takes as few as three gravitationally interacting bodies to break time-reversal symmetry., Science Alert, The movement of the three black holes can be so enormously chaotic that something as small as the Planck length will influence the movements., The n-body problem is a famous problem in astrophysics. It arises as you add more bodies to a gravitationally interacting system., Time-reversal symmetry.   

    From Science Alert: “Just Three Orbiting Black Holes Can Break Time-Reversal Symmetry, Physicists Find” 

    ScienceAlert

    From Science Alert

    25 MARCH 2020
    MICHELLE STARR

    1
    (wragg/Getty Images)

    Most of the laws of physics don’t care which direction time is travelling. Forwards, backwards… either way, the laws work exactly the same. Newtonian physics, general relativity – time is irrelevant to the mathematics: This is called time-reversal symmetry.

    In the real Universe, things get a bit messier. And now a team of scientists led by astronomer Tjarda Boekholt of the University of Aveiro in Portugal have shown that it takes as few as three gravitationally interacting bodies to break time-reversal symmetry.

    “Hitherto, a quantitative relation between chaos in stellar dynamical systems and the level of irreversibility remained undetermined,” they wrote in their paper.

    “In this work we study chaotic three-body systems in free fall initially using the accurate and precise n-body code Brutus, which goes beyond standard double-precision arithmetic. We demonstrate that the fraction of irreversible solutions decreases as a power law with numerical accuracy.”

    The n-body problem is a famous problem in astrophysics. It arises as you add more bodies to a gravitationally interacting system.

    The movements of two bodies of comparable size in orbit around a central point are relatively simple to mathematically predict, according to Newton’s laws of motion and Newton’s law of universal gravitation.

    However, once you add another body, things become tricky. The bodies start to gravitationally perturb each others’ orbits, introducing an element of chaos into the interaction. This means that, although solutions exist for special cases, there is no one formula – under Newtonian physics or general relativity – that describes these interactions with complete accuracy.

    Even within the Solar System, which we understand pretty well, we can only predict a few million years into the future. Chaos in the Universe is a feature, not a bug.

    When running n-body simulations, physicists sometimes return time-irreversibility in their results – in other words, running the simulations backwards doesn’t get them to the original starting point.

    What has been unclear is whether this is a result of the chaos of these systems, or problems with the simulations, leading to uncertainty over their reliability.

    So, Boekholt and his colleagues designed a test to figure this out. He and computational astrophysicist Simon Portegies Zwart of Leiden University in the Netherlands previously wrote an n-body simulation code called Brutus that uses brute-force computing power to reduce the magnitude of numerical errors.

    Now, they have used it to test the time-reversibility of a three-body system.

    “Since Newton’s equations of motion are time reversible, a forward integration followed by a backward integration of the same time should recover the initial realisation of the system (albeit with a sign difference in the velocities),” they wrote in their paper.

    “The outcome of a reversibility test is thus exactly known.”

    The three bodies in the system are black holes, and they were tested in two scenarios. In the first, the black holes started from rest, moving towards each other into complicated orbits, before one of the black holes is kicked out of the system.

    The second scenario starts where the first one ends, and is run backwards in time, trying to restore the system to its initial state.

    They found that, 5 percent of the time, the simulation could not be reversed. All it took was a disturbance to the system the size of a Planck length, which, at 0.000000000000000000000000000000000016 metres, is the smallest length possible.

    “The movement of the three black holes can be so enormously chaotic that something as small as the Planck length will influence the movements,” Boekholt said. “The disturbances the size of the Planck length have an exponential effect and break the time symmetry.”

    Five percent may not seem like much, but since you can never predict which of your simulations will fall within that five percent, the researchers have concluded that n-body systems are therefore “fundamentally unpredictable”.

    And they have shown that the problem is not with the simulations after all.

    “Not being able to turn back time is no longer just a statistical argument,” Portegies Zwart said. “It is already hidden in the basic laws of nature. Not a single system of three moving objects, big or small, planets or black holes, can escape the direction of time.”

    The research has been published in the Monthly Notices of the Royal Astronomical Society.

    See the full article here .


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  • richardmitnick 10:47 am on March 23, 2020 Permalink | Reply
    Tags: "It Looks Like That Interstellar Comet Came All The Way to The Solar System to Die", 2I/Borisov has been spotted spewing out material in two cometary outbursts., Science Alert   

    From Science Alert: “It Looks Like That Interstellar Comet Came All The Way to The Solar System to Die” 

    ScienceAlert

    From Science Alert

    23 MARCH 2020
    MICHELLE STARR

    1
    (NASA/ESA/David Jewitt/Paul Kalas)

    A comet that entered our Solar System from interstellar space may not make it out again. As it zooms away from the Sun, 2I/Borisov has been spotted spewing out material in two cometary outbursts.

    These outbursts show that the comet is disintegrating, according to Polish astronomers from the Jagiellonian University in Krakow and the University of Warsaw who recorded the activity.

    “This behaviour is strongly indicative of an ongoing nucleus fragmentation,” they wrote in a notice posted to Astronomers Telegram.

    2I/Borisov first drew the world’s attention at the end of August last year, when it was officially discovered whizzing through the Solar System on a trajectory that indicated an interstellar origin.

    Scientists later pored through observation data, and found images of the comet dating all the way back to December 2018. This wealth of additional data supported conclusions about the comet’s interstellar origins, and allowed for a more precise prediction of its future trajectory.

    What astronomers were particularly keen to see what happened after the comet reached perihelion – its closest approach to the Sun – on 8 December 2019.

    That’s because there are two types of comets in the Solar System. Short-period comets typically come from the Kuiper Belt or closer, and have an orbital period of less than 200 years. They are much more likely to stay intact when they go past the Sun.

    Long-period, or dynamically new comets come from farther away – the Oort cloud – and are more likely than short-period comets to break up. Analyses of 2I/Borisov’s colour and composition found it was very similar to long-period comets, so disintegration due to heating from the Sun was anticipated, but not guaranteed.

    “For Solar System comets, it is known that dynamically new comets are 10 times more likely to disintegrate than short-period comets, presumably due to their pristine state and weaker structural strength,” wrote researchers led by Quanzhi Ye from the University of Maryland last year.

    This would be seen as a change in brightness in the comet – and indeed, this is what has been observed. Between 5 and 9 March 2020, the comet brightened twice.

    But although it may be the end of the line for 2I/Borisov – a journey of an unconfirmed number of light-years across space – it’s not a sad one. As the comet disintegrates, observations of its spectrum will reveal its internal chemistry, including its nucleus.

    It’s an excellent opportunity to study the comet’s guts, and compare it to our Solar System comets, to see how similar or different they are.

    Since comets are thought to be a vital part of the emergence of life here on Earth, those comet guts could help us discover if the ingredients for life are common in our galaxy.

    So astronomers will be continuing to closely monitor 2I/Borisov’s activity.

    See the full article here .


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  • richardmitnick 10:33 am on March 23, 2020 Permalink | Reply
    Tags: "NASA Suspends Work on The New Moon Mission Rocket Due to Coronavirus Outbreak", Science Alert   

    From Science Alert: “NASA Suspends Work on The New Moon Mission Rocket Due to Coronavirus Outbreak” 

    ScienceAlert

    From Science Alert

    23 MARCH 2020

    NASA said it has suspended work on building and testing the rocket and capsule for its Artemis crewed mission to the Moon due to the rising number of coronavirus cases in the community.

    NASA ARTEMIS spacecraft depiction

    2
    The Lockheed Martin-built Orion capsule for the Artemis 1 mission to the Moon is declared finished. https://techcrunch.com

    The space agency is shutting down its Michoud Assembly Facility in New Orleans, where the Space Launch System rocket is being built, and the nearby Stennis Space Center, administrator Jim Bridenstine said late Thursday.

    “The change at Stennis was made due to the rising number of COVID-19 cases in the community around the center, the number of self-isolation cases within our workforce there, and one confirmed case among our Stennis team,” he said.

    “NASA will temporarily suspend production and testing of Space Launch System and Orion hardware. The NASA and contractors teams will complete an orderly shutdown that puts all hardware in a safe condition until work can resume.”

    The Space Launch System is a powerful deep space rocket to transport astronauts to the Moon and beyond while Orion is the crew module.

    The virus outbreak could hit US plans to return to the Moon by 2024.

    “We realize there will be impacts to NASA missions, but as our teams work to analyze the full picture and reduce risks we understand that our top priority is the health and safety of the NASA workforce,” Bridenstine said.

    A crewed return to the Moon is the first part of the Artemis program to set up a long-term colony and test technologies for a crewed mission to Mars in the 2030s.

    See the full article here .


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