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  • richardmitnick 9:45 pm on June 18, 2021 Permalink | Reply
    Tags: "Capricious Cosmos", , , , , Comets, , , , Merging neutron stars   

    From ESOblog (EU): Women in STEM-Cyrielle Opitom “Capricious Cosmos” 

    ESO 50 Large

    From ESOblog (EU)

    at

    European Southern Observatory [Observatoire européen austral][Europäische Südsternwarte] (EU) (CL)

    18 June 2021
    Science@ESO

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    Juan Carlos Muñoz Mateos.
    Juan Carlos Muñoz Mateos is Media Officer at ESO in Garching and editor of the ESO blog. He completed his PhD in astrophysics at Complutense University of Madrid[Universidad Complutense Madrid](ES) . Previously he worked for several years at ESO in Chile, combining his research on galaxy evolution with duties at Paranal Observatory.

    Astronomical observations are usually planned months in advance, which is not a problem as most celestial objects remain unchanged for millions if not billions of years. But certain astronomical phenomena can occur unexpectedly on timescales of just days –– sometimes even minutes. To learn how we can deal with these sudden events we have talked to three astronomers who study some of the most unpredictable phenomena in the Universe.

    “Comets are like cats: they have tails and they do precisely what they want.” This quote by David H. Levy, an amateur astronomer who co-discovered a comet that impacted on Jupiter in 1994, perfectly describes the capricious personality of comets –– large blocks of ice and rock that traverse the solar system.

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    A NASA Hubble Space Telescope (HST) image of comet Shoemaker-Levy 9, taken on May 17, 1994, with the Wide Field Planetary Camera 2 (WFPC2) in wide field mode.

    But these aren’t the only unpredictable objects out there. Violent supernova explosions, black holes gobbling material from closeby stars, or neutron stars smashing against each other are just a few examples of astronomical phenomena known for not caring about the daily routine of the astronomers who study them. How can we observe these events without even knowing when or where they will happen? Let’s find out.

    Celestial wanderers

    Cyrielle Opitom, a former ESO Fellow and now a Royal Astronomical Society (UK) Norman Lockyer Research Fellow at the University of Edinburgh (SCT), is very familiar with the changeable nature of comets –– fossils that allow us to study how our own solar system formed and evolved. “Comets are very unpredictable,” she says. “Some suddenly split into different fragments, crash into a planet, or become ten times brighter from one day to the next. And we are still trying to understand why those things are happening. That also makes comets very fun to study. You never know what to expect and it never gets boring.”

    When a comet gets close to the Sun, its ices become gaseous. This ejects dust particles as well, creating a huge envelope of dust and gas around the nucleus of the comet, called ‘coma’. Cyrielle uses spectroscopy, a technique that splits light into its constituent colours or wavelengths, “to detect molecules in the coma, and to know what cometary ices are made of.”

    But it’s hard to know in advance when a comet may undergo a sudden burst of activity. To address this, ESO and other observatories offer a type of observing programme called “Target of Opportunity”. “This allows us to decide in advance that we want to observe an outburst of activity, have the observations ready to be executed, and when an event is detected we can ask for the observations to be done within just a few days,” says Cyrielle.

    A Target of Opportunity still requires astronomers to submit an observing proposal months in advance describing their scientific idea, even if they don’t know when they will trigger the observations. “But there are events that we can’t predict, or new interesting comets that are discovered after the deadline for observing time proposals has passed.” For situations like these, observatories offer the opportunity to obtain observing slots using “Director’s Discretionary Time (DDT)”, which allows astronomers to submit an observing proposal on-the-fly for urgent scientific reasons. For instance, these DDT slots came in handy to observe 2I/Borisov, the first interstellar comet, immediately after its discovery, allowing astronomers to study this alien visitor while it was still close to the Earth.

    Comets can still surprise you even when you are already pointing a telescope at them, as Cyrielle knows all too well. In December 2018 she was observing comet 46P/Wirtanen with the ESPRESSO spectrograph at the UT3 telescope [1], part of ESO’s Very Large Telescope.

    “The comet was bright and very close to the Earth,” she says, “so it was quite big in the sky. However, when we tried to point the instrument at the comet, we could not find it.”

    As it turns out, the comet was too far from its predicted position. Luckily, she was observing it simultaneously with the UVES spectrograph on the UT2 telescope. “We managed to find it with UVES, which has a larger field of view.

    We computed the offset from the predicted position and finally found the comet with ESPRESSO as well. But our problems were not over: the comet was not moving the way we expected, so we had to constantly adjust the position of the telescope during the observations. Thanks to the great skills of our support astronomer we got amazing data in the end.”

    When black holes take a midnight snack

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    Combining observations done with ESO’s Very Large Telescope and NASA’s Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole.

    The black hole blows a huge bubble of hot gas, 1000 light-years across or twice as large and tens of times more powerful than the other such microquasars. The stellar black hole belongs to a binary system as pictured in this artist’s impression. Credit:L. Calçada/M.Kornmesser/ESO.

    Black holes may not be as evasive as comets, but they are still tricky to observe. Teo Muñoz-Darias, a Ramón y Cajal Fellow at the Institute of Astrophysics of the Canaries[Instituto de Astrofísica de Canarias] (ES), is trying to understand what makes black holes hungry. “I study systems called X-ray binaries,” he says, “where a normal star orbits a black hole at such close distance that the black hole steals material from the star.” But since both are rotating around each other, the material doesn’t fall directly into the black hole; instead, it forms an accretion disc around it. “Gas in the accretion disc gets really hot, up to ten million degrees, thus emitting highly energetic radiation like X-rays.”

    This doesn’t happen all the time though. “Most black holes are sleeping and they wake up every now and then,” Teo explains.“If there is little gas in the disc, it will just stay there orbiting the black hole. But when enough gas accumulates, it becomes hotter and friction increases; the gas then loses energy and spirals towards the black hole.” Not all the gas suffers that demise, though; sometimes it can leave the system via powerful winds and jets.

    When one of these systems becomes active, dedicated space telescopes will pick up the sudden burst of X-rays. Astronomers worldwide are notified about this and start collecting additional data from ground-based telescopes, quickly sharing their findings via The Astronomer’s Telegram. Teo constantly keeps an eye on this, as interesting targets can show up anytime. “Black holes don’t care about Saturdays, Sundays, or holidays,” he jokes. “In fact they tend to pick holidays!”

    Upon finding a suitable target, Teo triggers Target of Opportunity observations with various instruments, like the X-shooter spectrograph at ESO’s VLT.

    “X-shooter is probably the best instrument worldwide for this kind of science,” he says. “With it you are able to get a spectrum all the way from the ultraviolet to the near infrared in one go, and this is fantastic. It’s not only that you get a lot of data, but you get it simultaneously.” This is key with rapidly changing objects, as it allows astronomers to follow how they evolve at different colours without having to coordinate observations with separate instruments.

    Thanks to observations like these, Teo and his team could study in great detail the complex balance between gas accretion onto the black hole and gas being expelled outwards due to winds. They found that winds are present even when the system is asleep, and that when they are awake their activity can end prematurely when a lot of gas is removed.

    The most energetic explosions in the Universe

    When it comes to unpredictability, nothing beats gamma-ray bursts (GRBs) –– sudden flashes of high-energy gamma radiation. “GRBs are the brightest things known to science,” says Nial Tanvir, a professor at the University of Leicester (UK).

    “Some are produced when a massive star implodes at the end of its lifetime, leaving behind a neutron star or a black hole. Other GRBs are caused by the merger of two neutron stars. GRBs give us access to the most extreme physics that we know of in the Universe.”

    As opposed to comets and black holes feasting off closeby stars, which require astronomers to react within days, GRBs sometimes need to be observed minutes after they occur. “GRBs start out bright and decline in luminosity quickly,” Nial says. “So if you can get there early, there’s just so much more information that you can get with a shorter amount of telescope time. If you can get observations within minutes and then continue to monitor over a few hours, in some cases you see variability, which can tell you important things about the GRB and its environment.”

    To allow astronomers to react so quickly, ESO offers them a unique observing mechanism called “Rapid Response Mode”. When this mode is triggered, an alarm instantly goes off in the Paranal control room: the ongoing observations will be aborted –– if it’s safe to do so –– and the telescope will automatically slew towards the sky coordinates of the GRB. Unfortunately, this requires knowing the exact location of the GRB from the get go, which isn’t always the case.

    One of the most exciting events that Nial has studied was the first-ever detection of light from two merging neutron stars. On 17 August 2017 the LIGO and Virgo interferometers registered gravitational waves –– ripples in space-time –– passing through Earth. Two seconds later, the Fermi and INTEGRAL space telescopes detected a GRB coming from the same area of the sky.


    Both were the smoking-gun evidence of a kilonova: two neutron stars smashing against each other.

    As night fell in Chile, dozens of telescopes started to chase this unique event. “Neither the gravitational waves nor the gamma rays gave us a tremendously accurate localisation,” says Nial. So this was like looking for a needle in a haystack, scanning a large patch of the sky looking for a small dot that wasn’t there before. The Swope telescope at Las Campanas Observatory was the first one to locate the host galaxy: NGC4993, an elliptical galaxy about 140 million lightyears away.

    Five other teams found it independently during those hectic first couple of hours, including Nial’s group using ESO’s VISTA telescope [below].

    “You just did have that strong sense that you were sort of living through history, perhaps more so than anything else I’ve been involved with.” During the next few weeks, astronomers worldwide monitored the evolution of this object with pretty much every telescope they could, including 14 instruments from 7 ESO-related telescopes. “As the days went by this thing started to become redder and redder, just as predicted. The collision pulled very radioactive material out of the neutron stars, which then decayed to form a whole lot of elements heavier than iron like gold, platinum and uranium, whose origin had previously been quite mysterious.”

    It’s all about teamwork

    Observing these unpredictable events is only possible thanks to team spirit. In the case of the kilonova, for instance, astronomers barely had a couple of hours after sunset to observe it before it sank under the horizon. As Nial says, “The success of all of these campaigns really came down to the staff at the telescopes, who were doing their very best to squeeze in those observations in difficult circumstances.”

    But this is only part of the story, as good planning is also key. “ESO is not just Paranal or La Silla observatories,” explains Cyrielle. “It also has an amazing team at the User Support Department to help us prepare and adjust our observations, so that we make the best possible use of the instruments. When I was preparing observations of the interstellar comet 2I/Borisov, they helped me design unusual observations that spanned several months. Without them we could never have obtained such high-quality data to study an interstellar comet.”
    Note

    [1] Unlike other instruments, ESPRESSO isn’t physically attached to a Unit Telescope. The light from any UT, even all four of them, can be fed into the instrument.

    See the full article here .


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    European Southern Observatory [Observatoire européen austral][Europäische Südsternwarte] (EU) is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    European Southern Observatory [Observatoire européen austral][Europäische Südsternwarte] (EU) is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design,

    European Southern Observatory(EU) , Very Large Telescope at Cerro Paranal in the Atacama Desert •ANTU (UT1; The Sun ) •KUEYEN (UT2; The Moon ) •MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening star). Elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo. [/caption]

    ESO Very Large Telescope 4 lasers on Yepun (CL)

    European Southern Observatory(EU)/MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

    European Southern Observatory(EU) ExTrA telescopes at erro LaSilla at an altitude of 2400 metres.

     
  • richardmitnick 9:10 pm on March 5, 2021 Permalink | Reply
    Tags: "Comet Catalina suggests comets delivered carbon to rocky planets", , , , Comets, , , SOFIA- Stratospheric Observatory for Infrared Astronomy,   

    From University of Minnesota Twin Cities: “Comet Catalina suggests comets delivered carbon to rocky planets” 

    u-minnesota-bloc

    From University of Minnesota Twin Cities

    March 5, 2021

    Rhonda Zurn
    College of Science and Engineering, Twin Cities
    612-626-7959
    rzurn@umn.edu

    1
    This illustration of a comet from the Oort Cloud as it passes through the inner solar system with dust and gas evaporating into its tail. SOFIA’s observations of Comet Catalina reveal that it’s carbon-rich, suggesting that comets delivered carbon to the terrestrial planets like Earth and Mars as they formed in the early solar system. Credit: NASA/DLR SOFIA/Lynette Cook.

    In early 2016, an icy visitor from the edge of our solar system hurtled past Earth. It briefly became visible to stargazers as Comet Catalina before it slingshotted past the Sun to disappear forevermore out of the solar system.

    Among the many observatories that captured a view of this comet, which appeared near the Big Dipper, was the Stratospheric Observatory for Infrared Astronomy (SOFIA), NASA’s telescope on an airplane.

    NASA/DLR SOFIA modified Boeing 747 aircraft.

    Using one of its unique infrared instruments, SOFIA was able to pick out a familiar fingerprint within the dusty glow of the comet’s tail—carbon.

    Now this one-time visitor to our inner solar system is helping explain more about our own origins as it becomes apparent that comets like Catalina could have been an essential source of carbon on planets like Earth and Mars during the early formation of the solar system.

    New results from SOFIA, a joint project of NASA and the DLR German Aerospace Center, were published in the Planetary Science Journal.

    “Carbon is key to learning about the origins of life,” said the paper’s lead author, Charles “Chick” Woodward, an astrophysicist and professor in the University of Minnesota Twin Cities Minnesota Institute of Astrophysics. “We’re still not sure if Earth could have trapped enough carbon on its own during its formation, so carbon-rich comets could have been an important source delivering this essential element that led to life as we know it.”

    Frozen in Time

    Originating from the Oort Cloud at the farthest reaches of our solar system, Comet Catalina and others of its type have such long orbits that they arrive on our celestial doorstep relatively unaltered.

    Milky Way Galaxy from Sun to Interstellar Space beyond the Oort Cloud. Credit: NASA/ JPL-Caltech.

    This makes them effectively frozen in time, offering researchers rare opportunities to learn about the early solar system from which they come.

    SOFIA’s infrared observations were able to capture the composition of the dust and gas as it evaporated off the comet, forming its tail. The observations showed that Comet Catalina is carbon-rich, suggesting that it formed in the outer regions of the primordial solar system, which held a reservoir of carbon that could have been important for seeding life.

    While carbon is a key ingredient of life, early Earth and other terrestrial planets of the inner solar system were so hot during their formation that elements like carbon were lost or depleted. While the cooler gas giants like Jupiter and Neptune could support carbon in the outer solar system, Jupiter’s jumbo size may have gravitationally blocked carbon from mixing back into the inner solar system.

    Primordial Mixing

    So how did the inner rocky planets evolve into the carbon-rich worlds that they are today?

    Researchers think that a slight change in Jupiter’s orbit allowed small, early precursors of comets to mix carbon from the outer regions into the inner regions, where it was incorporated into planets like Earth and Mars.

    Comet Catalina’s carbon-rich composition helps explain how planets that formed in the hot, carbon-poor regions of the early solar system evolved into planets with the life-supporting element.

    “All terrestrial worlds are subject to impacts by comets and other small bodies, which carry carbon and other elements,” Woodward said. “We are getting closer to understanding exactly how these impacts on early planets may have catalyzed life.”

    Observations of additional new comets are needed to learn if there are many other carbon-rich comets in the Oort Cloud, which would further support that comets delivered carbon and other life-supporting elements to the terrestrial planets. As the world’s largest airborne observatory, SOFIA’s mobility allows it to quickly observe newly discovered comets as they make a pass through the solar system.

    SOFIA is a joint project of NASA and the DLR German Aerospace Center. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science, and mission operations in cooperation with the Universities Space Research Association, headquartered in Columbia, Maryland, and the German SOFIA Institute at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.

    See the full article here .

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    The University of Minnesota, Twin Cities (often referred to as the U of M, UMN, Minnesota, or simply the U) is a public research university in Minneapolis and Saint Paul, MN. The Twin Cities campus comprises locations in Minneapolis and St. Paul approximately 3 miles (4.8 km) apart, and the St. Paul location is in neighboring Falcon Heights. The Twin Cities campus is the oldest and largest in the University of Minnesota system and has the sixth-largest main campus student body in the United States, with 51,327 students in 2019-20. It is the flagship institution of the University of Minnesota System, and is organized into 19 colleges, schools, and other major academic units.

    The University was included in a list of Public Ivy universities in 2001. Legislation passed in 1851 to develop the university, and the first college classes were held in 1867. The university is categorized as a Doctoral University – Highest Research Activity (R1) in the Carnegie Classification of Institutions of Higher Education. Minnesota is a member of the Association of American Universities and is ranked 14th in research activity, with $881 million in research and development expenditures in the fiscal year ending June 30, 2015.

    University of Minnesota faculty, alumni, and researchers have won 26 Nobel Prizes and three Pulitzer Prizes. Notable University of Minnesota alumni include two vice presidents of the United States, Hubert Humphrey and Walter Mondale.

     
  • richardmitnick 9:35 am on November 2, 2020 Permalink | Reply
    Tags: "What is it with all that dust?", , , , , Comets, , , If white dwarfs should have cleared out all of this debris during the red giant phase then why do some of them seem to have closely orbiting dusty debris discs?, LSPM J0207+3331 – the oldest and coldest white dwarf known   

    From COSMOS(AU): “What is it with all that dust?” 

    Cosmos Magazine bloc

    From COSMOS(AU)

    31 October 2020
    Richard A Lovett

    Scientists solve another mystery about white dwarfs.

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    Artist’s impression of an asteroid is broken apart by LSPM J0207+3331 – the oldest and coldest white dwarf known. The system’s infrared signal is hypothesised to comprise two rings composed of dust supplied by crumbling asteroids. Credit: NASA’s Goddard Space Flight Centre / Scott Wiessinger.

    Scientists studying how comets and asteroids break up and vaporize if they get too close to their suns have resolved a conundrum about a class of stars known as white dwarfs.

    Embers of dying suns, white dwarfs form when a star, having run out of its nuclear fuel, first expands to enormous size then collapses into a dense, Earth-sized remnant.

    The initial, swollen size is called a red giant – and is large enough to consume planets as far out as Earth, and even Mars. It then implodes, leaving the white dwarf, which can initially be as hot as 50,000 degrees Celsius, until it gradually cools into obscurity.

    So far, so good. But astronomers have found that about 4% of them appear to be accompanied by clouds of dust.

    “This begs the question, if white dwarfs should have cleared out all of this debris during the red giant phase, then why do some of them seem to have closely orbiting dusty debris discs,” Jordan Steckloff, of the Planetary Science Institute (US), told this week’s virtual meeting of the American Astronomical Society’s Division for Planetary Sciences.

    Previously, he says, it was assumed that these discs were formed from planetesimals or asteroids that were far enough out to survive immolation in the red giant phase, but then fell inward, winding up so deep in the white dwarf’s gravity that they got ripped to shreds—something that occurs at a distance often referred to as the Roche limit.

    These shreds would then be dispersed into a “nice tight dusty debris disc” by the pressure of the light emitted by the star.

    But there was a big problem with that theory. One would expect younger white dwarfs to have less stable planetary systems, thanks to the gravitational mayhem that accompanied the effect of the red giant destroying all of the inner planets. In other words, they should have more worldlets falling toward the star to be ripped into dust.

    Also, younger white dwarfs are hotter – and therefore brighter – and should be better at making dusty discs out of the debris of shredded planetesimals.

    But that, Steckloff says, is not what astronomers have seen. Young super-hot white dwarfs do not have dust disks. “It’s only when white dwarfs cool to less than about 27,000 degrees Kelvin (27,000°C) that we actually see dusty debris discs start to appear.”

    The answer, he says, is something fairly obvious (in hindsight) but previously overlooked: if a planetesimal falls too close to a super-hot star, not only will it get shredded into dust, that dust will then be vaporized by the heat – a process he refers to as sublimation. The result: no dusty disc.

    “It needs to be outside the sublimation limit and inside the Roche limit,” he says.

    The Roche limit is determined by the star’s mass, but the sublimation limit is determined by its brightness, which declines as it cools.

    And, he says, it turns out that for young, super-hot white dwarfs, the Roche limit is inside the sublimation limit. I.e., anything that falls close enough to the star to be shredded will also be vaporized.

    It is only when the white dwarf cools to somewhere between 25,000 and 32,000 Celsius, he says, that this reverses – with the exact temperature depending on what type of minerals the dust is composed of. In fact, the figure comes even closer to 27,000 degrees if it is assumed that the dust in these discs is similar to the materials in our own Solar System’s asteroids.

    And that might be one of his most important findings.

    “The 27,000-degree limit suggests that the material that we find orbiting around white dwarfs is likely analogous to [asteroids] in our own Solar System,” he says.

    See the full article here .


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  • richardmitnick 11:23 am on May 19, 2020 Permalink | Reply
    Tags: , , , Comets, , , Why ESA and NASA's SOHO Spacecraft Spots So Many Comets"   

    From NASA: “Why ESA and NASA’s SOHO Spacecraft Spots So Many Comets” 


    From NASA

    May 19, 2020
    Sarah Frazier
    sarah.frazier@nasa.gov
    NASA’s Goddard Space Flight Center, Greenbelt, Md.


    ESA/NASA SOHO

    The Solar and Heliospheric Observatory, a joint mission between the European Space Agency and NASA, was not designed to find comets — its original goal was to study the Sun from its deep core to the outer layers of its atmosphere. But building new observatories can thankfully bring in discoveries that are entirely unexpected. Nearly 25 years since its launch, data from this space-based solar observatory has led to the discovery of well over half of all known comets — upwards of 3,950 new comets found.

    Though the SOHO team anticipated the spacecraft would discover some new comets, they never expected to find nearly 4,000 of them. The huge number of SOHO-discovered comets comes thanks to a combination of well-designed instruments, a long lifespan, the hard work of citizen scientists and a little bit of luck.

    “SOHO is uniquely placed in space and uniquely designed, and it’s these aspects of the spacecraft that allow it to see and discover so many comets,” said Karl Battams, a space scientist at the Naval Research Lab in Washington, D.C.

    SOHO carries an instrument called a coronagraph that uses a solid disk to block out the Sun’s bright face, revealing the much fainter outer atmosphere, the corona. Scientists use these images of the corona to study how this part of the atmosphere changes and to track occasional explosions of material from the Sun, called coronal mass ejections. SOHO’s vantage point between the Sun and Earth, about a million miles from Earth, gives it a constant view of the Sun’s atmosphere.

    SOHO’s coronagraph, known as LASCO, has both high sensitivity and a wide field of view, which turns out to be perfectly suited to see so-called “sungrazing comets” that fly too close to the Sun’s overwhelmingly bright face to be seen from Earth or with most other scientific instruments. And because SOHO has kept a steady eye on the corona – through which these comets fly — almost continuously for nearly 25 years, its data has revealed thousands of previously unknown comets: 3,953 as of May 2020.

    Almost all of SOHO’s comet discoveries have come from its coronagraph data, but a small handful of comets have been discovered in images from a different instrument on board: the SWAN instrument, a camera designed to look for interactions between the solar wind and hydrogen atoms in space. Some comets, including Comet SWAN discovered in April 2020, outgas large amounts of water — of which hydrogen is the main component — as they approach the Sun, making them visible to SWAN.


    Counting Comets
    Until 1979, humans had spotted fewer than a dozen sungrazing comets. As of 2020, we know of around 4,000. This sungrazing comet boom is thanks to ESA (European Space Agency) and NASA’s Solar and Heliospheric Observatory. Credits: NASA’s Goddard Space Flight Center.

    Around 85% of the thousands of comets discovered by SOHO are members of one family of comets: the Kreutz group. The Kreutz sungrazers are thought to be the remnants of a single giant comet, which, some thousands of years ago, flew close to the Sun and heated up, loosening the ice that bound it together. It fragmented into thousands of tiny comets that we know today as the Kreutz family. These relatively tiny remnants — most are around the size of a house — follow the path of the original Kreutz comet.

    SOHO’s data has proven a prime hunting ground for previously-undiscovered comets, but that doesn’t mean the going is easy. Most of the discoveries have been made through the painstaking work of citizen scientists with the Sungrazer Project, a NASA-funded project managed by Battams that grew out of early citizen science comet discoveries not long after SOHO launched in 1995.

    “After word spread that scientists were seeing new comets in the SOHO data, people went to the SOHO website and downloaded the images themselves and found a bunch of comets that the scientists had missed,” said Battams. “It got to the point where the project team was overwhelmed with the number of reports, so they created the Sungrazer Project to act as the hub for these discoveries.”

    If the rate of new comet discoveries continues at its usual pace, SOHO’s 4,000th new comet will likely be spotted sometime in summer 2020, according to Battams.

    The comets discovered in SOHO’s data have given scientists valuable insight into both comets as a whole as well as the environment they fly through. Because they fly so close to our star, most of the comets seen by SOHO don’t survive their trip around the Sun — they disintegrate near their closest approach because of the incredible heating caused by the intense sunlight.

    “When SOHO sees a comet, nearly every single one of them is in the process of being destroyed,” said Battams. “In that way, SOHO’s data has given us a peek into the end of life of a comet.”

    Beyond that, the comets spotted by SOHO can also act as celestial windsocks, revealing new information about the solar wind and solar atmosphere that they fly through.

    As comets approach the Sun, they become enveloped in a tail of gases liberated from the comet by heating caused by the intense sunlight. Some of the gases in this bright tail are ionized and are buffeted by the magnetized solar wind and magnetic fields in the Sun’s outer atmosphere, giving scientists the opportunity to measure the conditions in this region that would otherwise be invisible from afar.

    “We’ve used these images to validate models of the solar magnetic field and things like electron densities and temperatures,” said Battams. “There’s all kinds of unique science you can do by watching these icy bodies travel through this extreme environment.”

    SOHO is a cooperative effort between ESA and NASA. Mission control is based at NASA Goddard. SOHO’s Large Angle and Spectrometric Coronagraph Experiment, or LASCO, which is the instrument that provides most of the comet imagery, was built by an international consortium, led the U.S. Naval Research Lab in Washington, D.C.

    See the full article here .

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    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 10:02 am on September 11, 2019 Permalink | Reply
    Tags: "All comets in the solar system might come from the same place", , , , Comets, , ,   

    From Universiteit Leiden via phys.org: “All comets in the solar system might come from the same place” 


    From Universiteit Leiden

    via


    phys.org

    September 9, 2019
    Bryce Benda

    1
    (NASA/W. Liller)

    2
    This single frame Rosetta navigation camera image of Comet 67P/Churyumov-Gerasimenko was taken on 7 July 2015 from a distance of 154 km from the comet centre. Credit: ESA/Rosetta/NAVCAM

    A team of American and European scientists found that 14 different comets originated at the same time and place: a protoplanetary disk orbiting near our newly-formed Sun.

    All comets might share their place of birth, new research says. For the first time ever, astronomer Christian Eistrup applied chemical models to fourteen well-known comets, surprisingly finding a clear pattern. His publication has been accepted in the journal Astronomy & Astrophysics.

    Given that comet impacts are thought to be a potential source of organic materials on Earth, exploring this new cosmic origin story could lead to a better understanding of the origin of life.

    This particular survey of 14 comets is too small in scale to use as evidence that all comets came from the same time and place in the early Solar System.

    But it is an interesting starting point for future research, given that the researchers didn’t expect to find so much in common among their samples in the first place.

    Comets: balls of ice or more?

    Comets travel through our solar system and are composed of ice, dust, and small rock-like particles. Their nuclei can be as large as tens of kilometers across. “Comets are everywhere, and sometimes with very funky orbits around the Sun. In the past, comets even have hit the Earth,” Christian Eistrup says. “We know what comets consist of and which molecules are present in them. They vary in composition, but are normally seen as just one group of icy balls. Therefore, I wanted to know whether comets are indeed one group, or whether different subsets can be made.”

    A new take on comets

    “What if I apply our existing chemical models to comets?”, Eistrup thought during his Ph.D. at Leiden University. In the research team at Leiden Observatory, which included Kavli Prize winner Ewine van Dishoeck, he developed models to predict the chemical composition of protoplanetary discs—flat discs of gas and dust encompassing young stars. Understanding these discs can give insight into how stars and planets form. Conveniently, these Leiden models turned out to be of help in learning about comets and their origins.

    “I thought it would be interesting to compare our chemical models with published data on comets,” says the astronomer. “Luckily, I had the help of Ewine. We did some statistics to pin down if there was a special time or place in our young solar system, where our chemical models meet the data on comets.” This happened to be the case, and to a surprising extent. Where the researchers hoped for a number of comets sharing similarities, it turned out that all fourteen comets showed the same trend. “There was a single model that fitted each comet best, thereby indicating that they share their origin.”


    Credit: Leiden University

    Ice-cold

    And that origin is somewhere close to our young Sun, when it was still encircled by a protoplanetary disc and our planets were still forming. The model suggests a zone around the Sun, inside the range where carbon monoxide becomes ice—relatively far away from the nucleus of the young Sun. “At these locations, the temperature varies from 21 to 28 Kelvin, which is around minus 250 degrees Celsius. That’s very cold, so cold that almost all the molecules we know are ice.

    “From our models, we know that there are some reactions taking place in the ice phase—although very slowly, in a time-frame of 100,000 to 1 million years. But that could explain why there are different comets with different compositions.”

    But if comets come from the same place, how do they end up in different places and orbits in our solar system? “Although we now think they formed in similar locations around the young Sun, the orbits of some of these comets could be disturbed—for instance by Jupiter—which explains the different orbits.”

    Comet data hunter

    As befits a scientist, Eistrup places some side-notes to his publication. “With only fourteen comets, the sample is quite small. That’s why I’m currently hunting for data on many more comets, to run them through our models and further test our hypothesis.” Eistrup also hopes that astronomers that study the origin of our solar system and its evolution can use his results. “Our research suggests that comets have formed during the period they’re studying, so this new information might give them new insights.”

    He is also keen to get in touch with other comet researchers. “Because we show a new trend, I would like to discuss what other astronomers think of our research.”

    The seeds of life

    Comets and life on Earth, they go hand in hand. “We still don’t know how life on Earth began. But the chemistry on comets could lead to the production of organic molecules, including some building blocks for life. And if the right comet hits the right planet, with the right environment, life could start growing,” Eistrup concludes. So, interestingly, understanding the birth of comets potentially could help us understand the birth of life on Earth.

    See the full article here.

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    Universiteit Leiden Heijmans onderhoudt

    Universiteit Leiden was founded in 1575 and is one of Europe’s leading international research universities. It has seven faculties in the arts, sciences and social sciences, spread over locations in Leiden and The Hague. The University has over 6,500 staff members and 26,900 students. The motto of the University is ‘Praesidium Libertatis’ – Bastion of Freedom.

     
  • richardmitnick 9:57 am on April 22, 2019 Permalink | Reply
    Tags: , By simulating conditions in the early solar system researchers can calculate the ratio of heavy water to ordinary water when the planets were forming., Comets, From Astronomy Magazine: "Where did Earth's water come from?", Reservoirs with a high quantity of heavy water have a high D/H ratio while deuterium-poor reservoirs show a lower ratio., What do the samples suggest is the source of Earth’s water? Hallis suspects it came from the solar nebula., When hydrogen-rich and oxygen-rich minerals melt because of the mantle’s heat the resulting water can spew from the planet’s crust., When the European Giotto spacecraft visited Halley’s Comet in 1986 researchers noticed its heavy water content was higher than the gas in Earth’s part of the early solar system.   

    From Astronomy Magazine: “Where did Earth’s water come from?” 

    Astronomy magazine

    From Astronomy Magazine

    April 01, 2019
    Nola Taylor Redd

    Most astronomers believe asteroids carried water to early Earth. But new research suggests it may have come from even closer to home.

    1
    Asteroids could have carried water, locked away in their minerals, to a young Earth, depositing it through impacts during our planet’s early years. But this isn’t the only possible explanation for our watery world. Ron Miller for Astronomy.

    Karen Meech doesn’t spend a lot of time digging through Earth’s rocks. An astronomer by trade, she is usually behind the telescope, investigating comets and looking for hints about how Earth got its water. But a field trip to Iceland in 2004 ultimately sent her scrambling through the craters of Hawaii nearly a decade later in search of clues about the liquid that helped birth life on this planet.

    On that fateful Icelandic tour, Meech saw geothermal areas with gas billowing out of the ground. The guide told the group not to worry — it was only water. “Then she said, ‘This is probably primordial water,’ and it set a lightbulb off,” Meech says.

    The flavors of water

    The source of Earth’s water has been a long-standing mystery; Meech herself has been trying to solve it for at least 20 years. Most of that search has focused on sorting out the various isotopes of hydrogen that go into making the water — or “the flavor of water,” as Lydia Hallis of the University of Glasgow calls it. One of those “flavors” is heavy water, a form of water that incorporates deuterium, an isotope of hydrogen whose nucleus contains one proton and one neutron. Normal hydrogen lacks a neutron, so water with deuterium weighs more than ordinary water.

    By simulating conditions in the early solar system, researchers can calculate the ratio of heavy water to ordinary water when the planets were forming. On Earth, the observed ratio is higher than it would have been in the young solar system, leading many astronomers to suspect that the water was imported because the ratio should remain constant over time. Today, most scientists believe asteroids carried water to the young, dry Earth.

    Meech was suspicious of this idea because measurements of Earth’s deuterium-to-hydrogen (D/H) ratio, which is connected to the ratio of heavy water to normal, is generally based on the composition of today’s oceans. Reservoirs with a high quantity of heavy water have a high D/H ratio, while deuterium-poor reservoirs show a lower ratio.

    2
    Earth formed from the dust and gas of the nebula that surrounded our infant Sun. This artist’s concept shows the protoplanetary disk of material around a young star. The disk contains the individual components of water — hydrogen and oxygen — and water in both ice and vapor forms. NASA/JPL-Caltech.

    But Earth’s ratio should have changed over time. Like most planets, Earth probably lost some of its atmosphere to space, and the lighter hydrogen would be easier to strip from the planet than its heavier counterpart. Geological processes, such as the evaporation of water from reservoirs such as lakes and oceans, can also change the ratio, as can biological reactions, because lighter isotopes are used differently than heavier ones in metabolic processes. All of these processes would give the modern Earth a higher D/H ratio compared with when the planet was newly formed.

    When Meech heard that primordial water could be spouting from the surface in Iceland, she grew excited at the chance to study the earliest flavor of water. But after chatting with a geologist, she learned that the plumes actually came from more recent activity — they weren’t primordial after all. However, the geologist revealed that some rocky material brought up from Earth’s mantle does contain small traces of water. That material may never have mixed with the stuff on the surface and could represent Earth’s early water. No one had investigated the D/H ratio in those samples because the technology to do so was new. But the University of Hawaii, where Meech is based, had just purchased a new ion microprobe that might be able to do the job.

    U Hawaii Ion microprobe

    UH Researchers Shed New Light on the Origins of Earth’s Water 12 November 2015

    “I thought, wow, here’s a way we can actually measure the original fingerprints,” Meech says. “At that point, I got very excited.”

    In search of the culprit

    Earth and the rest of the planets formed inside a nest of gas left over from the birth of the Sun. This material, known as the solar nebula, contained all the elements that built the planets, and the compositions varied with distance from the Sun. The region near the star was too warm for some material to coalesce as ices, which instead formed in the outer part of the solar system. Around Earth, hydrogen and other elements could stick around only as a gas. Because the nebula was short-lived, most scientists suspect that Earth didn’t have enough time to collect these gases before they escaped into space. That idea, along with the planet’s high D/H ratio, led many to believe that Earth’s water must have arrived after Earth had cooled.

    When the European Giotto spacecraft visited Halley’s Comet in 1986, researchers noticed its heavy water content was higher than the gas in Earth’s part of the early solar system.

    3
    ESA Giotto spacecraft

    A new theory emerged: Comets could have carried water to early Earth. After the planets formed, the enormous bodies would continue to stir things up, with giant planets like Jupiter hurling some material toward the inner solar system. Icy objects that formed in the outer solar system could have been tossed at Earth to rain down as giant water-laden impacts.

    4
    Heavy water, or D2O, contains deuterium in place of hydrogen. Deuterium is an isotope of hydrogen whose nucleus contains one proton and one neutron, whereas normal hydrogen contains only a proton. The ratio of heavy water to normal water in a sample gives scientists information about how it formed — information researchers are now using to try to unravel the origin of Earth’s water. Astronomy: Roen Kelly.

    But as other missions probed more comets, it became clear that the amount of heavy water wasn’t consistent among them. In fact, most of the comets’ heavy water ratios were far too high to be responsible for dropping water on Earth. Another culprit must be responsible.

    Comets weren’t the only thing that the gas giants tossed around. As Jupiter plowed through the asteroid belt early in our solar system’s history, it scattered the rocky debris in all directions. Like comets, some of the material rained down on Earth. Unlike comets, asteroids don’t lock up water as ice. Instead, they trap its components — hydrogen and oxygen — inside minerals. Also, the heavy water content in asteroids falls much closer to Earth’s current ratio. That’s why asteroids are the leading suspect for the source of our planet’s water.

    “Really, we’re not talking about water; we’re talking about hydrogen,” says Anne Peslier, a geochemist at NASA’s Johnson Space Center. Peslier studies the geochemistry of Earth’s mantle and the other terrestrial planets, including the hydrogen trapped within minerals.

    When Earth formed, the hydrogen surrounding the growing planet was captured in its rocks and minerals. When hydrogen-rich and oxygen-rich minerals melt because of the mantle’s heat, the resulting water can spew from the planet’s crust.

    Most of the mantle is rocky, and enormous quantities of hydrogen and oxygen could be trapped inside. Researchers estimate that as much as 10 oceans of water may exist within the mantle.

    Erupting volcanoes usually bring up magma from the upper part of Earth’s mantle, the region closer to the surface. This material is more likely to be polluted by hydrogen from the crust, which contains the same higher D/H ratios measured in the oceans today. More pristine samples lie much farther down in the mantle. Although it’s hot there, less than 20 percent of the mantle rock has melted, Peslier says. When the melted material erupts, it can have a violent effect on the solid rock.

    “If [the lavas] go fast enough and brutally enough, they sometimes break off pieces of what they are traversing along the way,” Peslier says. She describes the result — called mantle xenolith, after the Greek word for “foreign rock” — as crystals of bright green olivine and black pyroxene embedded in the black lava.

    If the hydrogen-rich olivine crystals were captured early enough during Earth’s formation and remained undisturbed for the planet’s 4.5 billion-year lifetime, they could reveal how much the ancient ratios of heavy and normal water shifted, if they changed at all. The tiny time capsules could provide answers to the long-standing questions regarding the source of Earth’s water.

    But first, they had to be found.

    Hunting primordial water

    While Meech knows a great deal about water in the solar system, she wasn’t as familiar with rocks on Earth. She pulled in Hallis, then a postdoctoral student, to lead geological excavations in a hunt for those early fingerprints of normal and heavy water. Hallis was intrigued by the chance to scramble across craters in Hawaii and along the shores of Baffin Island in Canada in search of clues. Baffin is one of the few places where Earth’s deep mantle is accessible. The chain of eruptions that formed the island also created Greenland and Iceland. “The Baffin Island samples are the most pristine examples that we have of the deep mantle,” Hallis says.

    Hallis also received samples collected by Don Francis, now an emeritus professor at McGill University in Montreal, from a tiny uninhabited island called Padloping, off the eastern coast of Canada and northwest of Baffin Island. According to Hallis, Francis collected the first of his samples in 1985. The isolation of Padloping Island meant that researchers had to travel there by boat and set up camp. The sheer cliffs made falling rocks plentiful, and Francis picked up the best-looking minerals from the beach. A return trip in 2004 netted even more samples. “Something I would really like to do is go back [to Padloping Island],” Hallis says. The imposing cliffs make it challenging to collect samples, but if she could obtain some from the steep overhangs, she would be able to pinpoint where and when the material rose to the surface.

    5
    Green olivine crystals in lava can contain and protect hydrogen collected during Earth’s formation, allowing researchers to determine its ratio of deuterium to hydrogen.
    S. Rae/Flickr.

    With the well-preserved samples in hand, Hallis and her colleagues began to systematically destroy them. The rocks were ground up into sandlike powder. Using the microprobe, the scientists sorted the enclosed crystals by color.

    Meech helped to categorize the crystals. “I found it hard to manipulate the tiny little bits of sand without spilling them on the floor,” she admits ruefully.

    Part of the process involved ensuring the samples were stripped from the mantle rather than the crust as the volcanic plume burst upward. Previous studies of the Baffin Island minerals suggested that they came from the mantle’s depths, and mineralogical evidence revealed that the samples Hallis had in the lab were most likely pristine. The tiny glass beads were protected in part by olivine crystals, which act as a barrier to prevent weathering once the rocks are on the surface. Even so, they weren’t entirely perfect.

    “Even with the most pristine samples that we have, it’s not 100 percent exactly deep mantle,” Hallis says. “It’s always going to have some incorporation of the [upper] mantle in there, just because it has to travel through so much of the mantle to get to the surface.”

    While the Baffin Island samples were free of crust pollution, the team wasn’t so fortunate with the rocks gathered near their university. The Hawaiian minerals had suffered from weathering and had been heavily affected by surface water, most likely rain. The pollution kept these samples from revealing the flavors of pristine water.

    With the first fingerprints of Earth’s water finally taken, Meech and Hallis began to compare them with other samples. Hallis expected to observe a heavy water content closer to the meteorites thought to have delivered water to the young planet. Instead, the samples weighed in with about 25 percent less heavy water compared with normal water — far less than expected.

    “That was a bit of a surprise,” Hallis says. “It suggests that carbonaceous chondrites [a class of meteorites] are not a good fit for the source of Earth’s water.” While meteorites may have provided some of Earth’s water, she doesn’t think that they delivered all of it.

    The source of Earth’s water

    What do the samples suggest is the source of Earth’s water? Hallis suspects it came from the solar nebula. While many scientists argue that the nebula would have dissipated within 6 million years — long before our planet could have grown large enough to capture it — she points out that several young stars have been found with gas around them for as long as 10 million years. That would give the tiny rocks that ultimately built Earth enough time to incorporate elements like hydrogen and nitrogen into their structure. Hallis says nitrogen and hydrogen in the solar system tend to follow one another — “If you have a certain flavor of hydrogen, you have a certain flavor of nitrogen,” she says.

    “Perhaps you still have pockets in the Earth that have preserved this initial hydrogen source,” says Zachary Sharp, a researcher at the University of New Mexico who also suspects that Earth’s D/H ratio has shifted over time.

    7
    Geysers such as Strokkur in Iceland inspired Karen Meech to hunt for Earth’s primordial water. Although such geysers do not spew the unaltered early water needed to pursue this line of study, other geological processes, such as volcanic plumes, do. Ivan Sabljak/Wikimedia Commons.

    Hallis’ results aren’t the only ones to suggest that Earth may have picked up the bulk of its water from the start. While the Moon was once thought to be completely dry, recent re-examinations of Apollo Moon rocks have revealed traces of water. The leading theory for the Moon’s formation is that it was created when a Mars-sized object slammed into the young Earth. Liquid water on the surface would have been vaporized, leading many to conclude that Earth had to pick up more water from elsewhere. But the low D/H ratios from the lunar samples suggest that the Moon could have collected the water in minerals locked in its interior, a region neither comets nor asteroids could have polluted. Later volcanic eruptions hurled that material to the surface, to be returned to Earth by astronauts.

    Why is this important? The high temperatures post-collision would have been similar to those found in the solar nebula, Hallis says. That helps to make the case that even in the hot early solar system, volatiles and water could be accreted.

    But hydrogen comes in heavy and light flavors, so doesn’t that mean the ratio could change in either direction? Not really, according to Sharp, who has revisited the idea that most of Earth’s water may have been collected from the nebula rather than later collisions. “It’s easy to increase the isotopic ratio of the samples, but it’s difficult to lower them,” he says. That’s because the lighter hydrogen is easier to remove. For instance, hydrogen rises more easily to the top of the atmosphere, where the solar wind can strip it away. The heavier deuterium tends to stay closer to the ground.

    Asteroids are also providing hints that Earth’s water may have come from the gas that birthed the planets. Studies of meteorites from the large asteroid Vesta have revealed ratios of heavy water similar to the Baffin Island estimates.

    “Now that we are finding low values in Earth, the Moon, and Vesta, and also in the water reservoir of the asteroids, now maybe the [nebula] story is possible,” says Alice Stephant of Arizona State University, who studies Vesta. “It seems like they all share a common reservoir that is lower [in deuterium] than what we thought.”

    8
    Padloping Island is isolated, uninhabited, and home to what may be some of Earth’s oldest rock. Future expeditions to this island in Canada may confirm preliminary findings that our Sun’s protoplanetary nebula may have stuck around long enough for a forming Earth to capture hydrogen — a building block of water. Doc Searls/Flickr.

    The smoking gun

    The lower D/H ratios revealed by Hallis, Meech, and their colleagues are not yet widely accepted. Conel Alexander, a cosmo-chemist at the Carnegie Institution of Washington, says there are two reasons why other researchers didn’t immediately change their minds about the source of Earth’s water.

    One argument against the results stems from how Hallis extrapolated the isotopes and elemental abundances in her measurements; Alexander says some scientists disagree with how the final numbers play out using her method. The other issue is how Hallis explained her results. “Lydia’s interpretation was unique,” Alexander says. “There may be other ways of getting hydrogen into the melt inclusions that she was measuring.”

    Alexander’s chief concern stems from the fact that only a single source of rocks — the Baffin Island samples — was used to estimate the entire planet’s ancient ratios. “The bulk of Earth may have a completely different composition, and there may be something weird about ocean islands’ basalts,” he says. He hopes that other scientists will follow Hallis’ lead and measure the D/H ratio from a variety of deep-mantle plumes.

    Hallis is ready to take her own trip to Padloping Island to collect more samples. One thing she would like to do is investigate not just the hydrogen involved, but also the nitrogen. But analyzing the nitrogen in samples is more difficult than hunting down hydrogen, partly because there is even less nitrogen in these samples than hydrogen. Measuring nitrogen also requires instruments capable of very high precision. Hallis says it’s pushing the limit of what current technology can do.

    Alexander says that Hallis’ goal of hunting down nitrogen from future samples will also help firm up any doubts about the primordial nature of the Baffin Island samples. “If she can show that there is both light hydrogen and light nitrogen in these inclusions, I think that would be a smoking gun,” he says.
    “If the nitrogen follows the hydrogen, then we proved our theory that [the samples] are primitive,” Hallis says.

    See the full article here .


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  • richardmitnick 2:34 pm on October 20, 2017 Permalink | Reply
    Tags: , , , Comets, , ,   

    From Universe today: “Where Do Comets Come From? Exploring the Oort Cloud” 

    universe-today

    Universe Today

    19 Oct , 2017
    Fraser Cain

    Oort cloud Image by TypePad, http://goo.gl/NWlQz6


    Oort Cloud NASA

    Oort Cloud, The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA, Universe Today

    Before I get into this article, I want to remind everyone that it’s been several decades since I’ve been able to enjoy a bright comet in the night sky. I’ve seen mind blowing auroras, witnessed a total solar eclipse with my own eyeballs, and seen a rocket launch. The Universe needs to deliver this bright comet for me, and it needs to do it soon.

    By writing this article now, I will summon it. I will create an article that’ll be hilariously out of date in a few months, when that bright comet shows up.

    Like that time we totally discovered a supernova in the Virtual Star Party, by saying there wasn’t a supernova in that galaxy, but there was, and we didn’t get to make the discovery.

    Anyway, on to the article. Let’s talk about comets.

    See the full article here .

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  • richardmitnick 8:53 am on August 31, 2017 Permalink | Reply
    Tags: , , , Comets, , deflected comets and a closer look at the triggers of cosmic disaster, , Heavy stellar traffic, , TRAPPIST–South national telescope at ESO's La Silla Observatory   

    From Max Planck Institute for Astronomy: “Heavy stellar traffic, deflected comets, and a closer look at the triggers of cosmic disaster” 

    Max Planck Institute for Astronomy

    Max Planck Institute for Astronomy

    August 31, 2017

    Science Contact
    Bailer-Jones, Coryn
    Coryn Bailer-Jones
    Phone: (+49|0) 6221 528-224
    calj@mpia.de

    Public Information Officer
    Markus Pössel
    Public Information Officer
    Phone:(+49|0) 6221 528-261
    poessel@hda-hd.de

    4
    Image of the Week
    Close stellar encounters from the first Gaia data release
    Figure 1: The open circles show the time (horizontal axis) and distance (vertical axis) of the closest approach of stars to the Sun. Negative times indicate times in the past from today. Each point has been calculated as the median of the distribution of a swarm of surrogate particles which have been integrated through a Galactic potential. The “error” bars show the limits of the 5% and 95% percentiles of these distributions (which together form an asymmetric 90% confidence interval). That is, the swarm is used to propagate the uncertainties in the TGAS measurements to uncertainties in the perihelion parameters. The background colour (scale on the right) indicates the estimated completeness of the TGAS survey. That is, if all TGAS stars had radial velocities (and most do not), this gives the probability that a star with any particular perihelion parameters would be present in TGAS. Image credit: Coryn Bailer-Jones

    1
    Image of the Comet C/2012 S1 (ISON), taken with the TRAPPIST–South national telescope at ESO’s La Silla Observatory on the morning of Friday 15 November 2013, whose likely origin is the Oort cloud. This comet is definitely not colliding with Earth, but it shows the typical appearance of comets entering the inner solar system, including the typical tail made of gas and dust. Image: TRAPPIST/E. Jehin/ESO


    ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    As stars pass close by our solar system, they can nudge comets from the distant Oort cloud into the inner regions around the Sun. Thus, stellar encounters are an important factor in determining the risk of large cosmic impacts on Earth. Now, Coryn Bailer-Jones from the Max Planck Institute for Astronomy has used data from the ESA satellite Gaia to give the first systematic estimate of the rate of such close stellar encounters. Every million years, up to two dozen stars pass within a few light-years of the Sun, making for a near-constant state of perturbation. The results have been published in the journal Astronomy & Astrophysics.

    Oort Cloud NASA

    ESA/GAIA satellite

    Comets colliding with Earth are among the more violent and extensive cosmic catastrophes that can befall our home planet. The best known such impact is the one which, 66 million years ago, caused or at least hastened the demise of the dinosaurs (although it is not known whether the blame in this case falls on a comet or an asteroid).

    It must be said that, to the best of current knowledge, impacts with regional or even global consequences are exceedingly rare, and occur at a rate of no more than one per million years. Also, monitoring systems give us a fairly complete inventory of larger asteroids and comets, none of which is currently on a collision course with Earth.

    Still, the consequences are serious enough that studies of the causes of comet impacts are not purely academic. The prime culprits are stellar encounters: stars passing through our Sun’s cosmic neighborhood. The outskirts of our solar system are believed to host a reservoir of cold and icy objects – potential comets – known as the Oort cloud. The gravitational influence of passing stars can nudge these comets inwards, and some will begin a journey all the way to the inner solar system, possibly on a collision course with Earth. That is why knowledge of these stellar encounters and their properties has a direct impact on risk assessment for comet impacts.

    Now, Bailer-Jones has published the first systematic estimate of the rate of such stellar encounters. The new result uses data from the first data release (DR1) of the Gaia mission that combines new Gaia measurements with older measurements by ESA’s Hipparcos satellite. Crucially, Bailer-Jones modeled each candidate for a close encounter as a swarm of virtual stars, showing how uncertainties in the orbital data will influence the derived rate of encounters.

    Bailer-Jones found that within a typical million years, between 490 and 600 stars will pass the Sun within a distance of 16.3 light-years (5 parsecs, to use a unit more common in professional astronomy) or less. Between 19 and 24 stars will pass at 3.26 light-years (1 parsec) or less. All these hundreds of stars would be sufficiently close to nudge comets from the Oort cloud into the solar system. The new results are in the same ballpark as earlier, less systematic estimates that show that when it comes to stellar encounters, traffic in our cosmic neighborhood is rather heavy.

    The current results are valid for a period of time that reaches about 5 million years into the past and into the future. With Gaia’s next data release, DR2 slated for April 2018, this could be extended to 25 million years each way. However, astronomers intending to go even further and search for the stars that might be responsible for hurling a comet towards the dinosaurs will need to know our home galaxy and its mass distribution in much more detail than we currently do – a long-term goal of the researchers involved in Gaia and related projects.
    Background information

    The research described here is published as C. A. L. Bailer Jones, The completeness-corrected rate of stellar encounters with the Sun from the first Gaia data release in the journal Astronomy & Astrophysics.

    E-print on arXiv
    ESA picture of the week
    ESA press release

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  • richardmitnick 2:06 pm on July 25, 2017 Permalink | Reply
    Tags: , , , Comets, , , , ,   

    From JPL: “Large, Distant Comets More Common Than Previously Thought” 

    NASA JPL Banner

    JPL-Caltech

    July 25, 2017
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6425
    elizabeth.landau@jpl.nasa.gov

    1
    This illustration shows how scientists used data from NASA’s WISE spacecraft to determine the nucleus sizes of comets. They subtracted a model of how dust and gas behave in comets in order to obtain the core size. Credit: NASA/JPL-Caltech.

    2
    An animation of a comet. Credit: NASA/JPL-Caltech.

    Comets that take more than 200 years to make one revolution around the Sun are notoriously difficult to study. Because they spend most of their time far from our area of the solar system, many “long-period comets” will never approach the Sun in a person’s lifetime. In fact, those that travel inward from the Oort Cloud — a group of icy bodies beginning roughly 186 billion miles (300 billion kilometers) away from the Sun — can have periods of thousands or even millions of years.

    Oort Cloud NASA

    NASA’s WISE spacecraft, scanning the entire sky at infrared wavelengths, has delivered new insights about these distant wanderers.

    NASA/WISE Telescope

    Scientists found that there are about seven times more long-period comets measuring at least 0.6 miles (1 kilometer) across than had been predicted previously. They also found that long-period comets are on average up to twice as large as “Jupiter family comets,” whose orbits are shaped by Jupiter’s gravity and have periods of less than 20 years.

    Researchers also observed that in eight months, three to five times as many long-period comets passed by the Sun than had been predicted. The findings are published in The Astronomical Journal.

    “The number of comets speaks to the amount of material left over from the solar system’s formation,” said James Bauer, lead author of the study and now a research professor at the University of Maryland, College Park. “We now know that there are more relatively large chunks of ancient material coming from the Oort Cloud than we thought.”

    The Oort Cloud is too distant to be seen by current telescopes, but is thought to be a spherical distribution of small icy bodies at the outermost edge of the solar system. The density of comets within it is low, so the odds of comets colliding within it are rare. Long-period comets that WISE observed probably got kicked out of the Oort Cloud millions of years ago. The observations were carried out during the spacecraft’s primary mission before it was renamed NEOWISE and reactivated to target near-Earth objects (NEOs).

    “Our study is a rare look at objects perturbed out of the Oort Cloud,” said Amy Mainzer, study co-author based at NASA’s Jet Propulsion Laboratory, Pasadena, California, and principal investigator of the NEOWISE mission. “They are the most pristine examples of what the solar system was like when it formed.”

    Astronomers already had broader estimates of how many long-period and Jupiter family comets are in our solar system, but had no good way of measuring the sizes of long-period comets. That is because a comet has a “coma,” a cloud of gas and dust that appears hazy in images and obscures the cometary nucleus. But by using the WISE data showing the infrared glow of this coma, scientists were able to “subtract” the coma from the overall comet and estimate the nucleus sizes of these comets. The data came from 2010 WISE observations of 95 Jupiter family comets and 56 long-period comets.

    The results reinforce the idea that comets that pass by the Sun more often tend to be smaller than those spending much more time away from the Sun. That is because Jupiter family comets get more heat exposure, which causes volatile substances like water to sublimate and drag away other material from the comet’s surface as well.

    “Our results mean there’s an evolutionary difference between Jupiter family and long-period comets,” Bauer said.

    The existence of so many more long-period comets than predicted suggests that more of them have likely impacted planets, delivering icy materials from the outer reaches of the solar system.

    Researchers also found clustering in the orbits of the long-period comets they studied, suggesting there could have been larger bodies that broke apart to form these groups.

    The results will be important for assessing the likelihood of comets impacting our solar system’s planets, including Earth.

    “Comets travel much faster than asteroids, and some of them are very big,” Mainzer said. “Studies like this will help us define what kind of hazard long-period comets may pose.”

    NASA’s Jet Propulsion Laboratory in Pasadena, California, managed and operated WISE for NASA’s Science Mission Directorate in Washington. The NEOWISE project is funded by the Near Earth Object Observation Program, now part of NASA’s Planetary Defense Coordination Office. The spacecraft was put into hibernation mode in 2011 after twice scanned the entire sky, thereby completing its main objectives. In September 2013, WISE was reactivated, renamed NEOWISE and assigned a new mission to assist NASA’s efforts to identify potentially hazardous near-Earth objects.

    For more information on WISE, visit:

    https://www.nasa.gov/wise

    See the full article here .

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 9:02 am on April 4, 2017 Permalink | Reply
    Tags: , , , Comets,   

    From Astronomy Now: “See a trio of comets in the April sky” 

    Astronomy Now bloc

    Astronomy Now

    2 April 2017
    Ade Ashford

    1
    Comet 41P/Tuttle–Giacobini–Kresák in the constellation of Draco was about magnitude +6.5 on the night of 1-2 April when captured in this three-minute integration with a colour Starlight Xpress Ultrastar camera at the f/2 HyperStar focus of the author’s Celestron C11 Schmidt-Cassegrain telescope. AN image by Ade Ashford.

    Despite the glow of a waxing Moon, early April is a good time to catch a glimpse of two interesting comets that are currently circumpolar from the British Isles, meaning that they are sufficiently close to the North Celestial Pole such that they neither rise or set, visible throughout the hours of darkness.

    Comet 41P/Tuttle–Giacobini–Kresák, a periodic comet that orbits the Sun every 5.4 years, is predicted to fade from magnitude +6.7 to +7.6 during the month. Comet 41P passes just 0.6 degrees north of Thuban, otherwise known as alpha (α) Draconis, at 2am BST on 3 April. By 11 April, 41P lies between eta (η) and theta (θ) Draconis; then the comet passes just 0.6 degrees from beta (β) Draconis – the magnitude +2.8 star known as Rastaban in the head of the celestial dragon – eight days later.

    4
    Comets 41P/Tuttle–Giacobini–Kresák in Draco and C/2015 V2 (Johnson) in Hercules are very well placed for Northern Hemisphere observers during April — particularly in the dark of the Moon. Click on the graphic for a detailed PDF finder chart suitable for printing and use outside at the telescope. AN graphic and finder chart by Ade Ashford.

    Comet 41P crosses the border into neighbouring Hercules on 20 April, a constellation where another bright comet resides this month. C/2015 V2 (Johnson) is a hyperbolic comet destined to leave the Solar System but predicted to brighten a full magnitude to +7.4 by the end of April. C/2015 V2 lies between naked-eye stars tau (τ) and upsilon (υ) Herculis at 12am BST on 22 April, and between the latter and phi (φ) Herculis on 25 April.

    5
    Displaying more of a tail than Comet 41P, C/2015 V2 (Johnson) in the constellation of Hercules was about magnitude +8 on the night of 1-2 April when captured in this seven-minute integration with a colour Starlight Xpress Ultrastar camera at the f/2 HyperStar focus of the author’s Celestron C11 Schmidt-Cassegrain telescope. AN image by Ade Ashford.

    There’s also a bright comet in the morning sky. C/2017 E4 (Lovejoy) was discovered by Australian comet hunter Terry Lovejoy last month and is currently a seventh-magnitude object in eastern Pegasus, currently some 7 degrees northeast of magnitude +2.4 star epsilon (ε) Pegasi, otherwise known as Enif. C/2017 E4 (Lovejoy) presently rises in the east-northeast around 3am BST from the British Isles.

    See the full article here .

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