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  • richardmitnick 6:03 am on July 21, 2021 Permalink | Reply
    Tags: "Tail without a comet-the dusty remains of Comet ATLAS", , , , European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU), ,   

    From Royal Astronomical Society (UK) : “Tail without a comet-the dusty remains of Comet ATLAS” 

    From Royal Astronomical Society (UK)


    Media contacts:
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    Science contact:
    Dr. Lorenzo Matteini
    Space and Atmospheric Physics group
    Imperial College London

    A serendipitous flythrough of the tail of a disintegrated comet has offered scientists a unique opportunity to study these remarkable structures, in new research presented today at the National Astronomy Meeting 2021.

    Hubble Space Telescope image of comet C/2019 Y4 (ATLAS), taken on April 20 2020, providing the sharpest view to date of the breakup of the solid nucleus of the comet. Hubble’s eagle-eye view identifies as many as 30 separate fragments, and distinguishes pieces that are roughly the size of a house. Before the breakup, the entire nucleus of the comet may have been the length of one or two football fields. The comet was approximately 91 million miles (146 million kilometres) from Earth when the image was taken. Credit: National Aeronautics Space Agency (US) / European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) / Space Telescope Science Institute (US) / D. Jewitt (University of California-Los Angeles (US)). Licence type Attribution (CC BY 4.0)

    Comet ATLAS fragmented just before its closest approach to the Sun last year, leaving its former tail trailing through space in the form of wispy clouds of dust and charged particles. The disintegration was observed by the Hubble Space Telescope in April 2020 [see story below], but more recently the ESA spacecraft Solar Orbiter has flown close to the tail remnants in the course of its ongoing mission.

    ESA-United Space for Europe

    European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)
    “Solar Orbiter to pass through the tails of Comet ATLAS”

    ESA’s Solar Orbiter will cross through the tails of Comet ATLAS during the next few days. Although the recently launched spacecraft was not due to be taking science data at this time, mission experts have worked to ensure that the four most relevant instruments will be switched on during the unique encounter.

    Solar Orbiter was launched on 10 February 2020. Since then, and with the exception of a brief shutdown due to the coronavirus pandemic, scientists and engineers have been conducting a series of tests and set-up routines known as commissioning.

    The completion date for this phase was set at 15 June, so that the spacecraft could be fully functional for its first close pass of the Sun, or perihelion, in mid-June. However, the discovery of the chance encounter with the comet made things more urgent.

    Serendipitously flying through a comet’s tail is a rare event for a space mission, something scientists know to have happened only six times before for missions that were not specifically chasing comets. All such encounters have been discovered in the spacecraft data after the event. Solar Orbiter’s upcoming crossing is the first to be predicted in advance.

    It was noticed by Geraint Jones of the UCL Mullard Space Science Laboratory (UK), who has a 20-year history of investigating such encounters. He discovered the first accidental tail crossing in 2000, while investigating a strange disturbance in data recorded by the ESA/NASA Ulysses Sun-studying spacecraft in 1996. This study revealed that the spacecraft had passed through the tail of Comet Hyakutake, also known as ‘The Great Comet of 1996’. Soon after the announcement, Ulysses crossed the tail of another comet, and then a third one in 2007.

    Earlier this month, realising that Solar Orbiter was going to be 44 million kilometres downstream of Comet C/2019 Y4 (ATLAS) in just a matter of weeks, Geraint immediately alerted the ESA team.

    Solar Orbiter is equipped with a suite of 10 in-situ and remote-sensing instruments to investigate the Sun and the flow of charged particles it releases into space – the solar wind. Fortuitously, the four in-situ instruments are also perfect for detecting the comet’s tails because they measure the conditions around the spacecraft, and so they could return data about the dust grains and the electrically charged particles given off by the comet. These emissions create the comet’s two tails: the dust tail that is left behind in the comet’s orbit and the ion tail that points straight away from the Sun.

    Solar Orbiter will cross the ion tail of Comet ATLAS on 31 May–1 June, and the dust tail on 6 June. If the ion tail is dense enough, Solar Orbiter’s magnetometer (MAG) might detect the variation of the interplanetary magnetic field because of its interaction with ions in the comet’s tail, while the Solar Wind Analyser (SWA) could directly capture some of the tail particles.

    When Solar Orbiter crosses the dust tail, depending on its density – which is extremely difficult to predict – it is possible that one or more tiny dust grains may hit the spacecraft at speeds of tens of kilometres per second. While there is no significant risk to the spacecraft from this, the dust grains themselves will be vaporised on impact, forming tiny clouds of electrically charged gas, or plasma, which could be detected by the Radio and Plasma Waves (RPW) instrument.

    “An unexpected encounter like this provides a mission with unique opportunities and challenges, but that’s good! Chances like this are all part of the adventure of science,” says Günther Hasinger, ESA Director of Science.

    One of those challenges was that the instruments seemed unlikely to all be ready in time because of the commissioning. Now, thanks to a special effort by the instrument teams and ESA’s mission operations team, all four in-situ instruments will be on and collecting data, even though at certain times the instruments will need to be switched back into commissioning mode to ensure that the 15 June deadline is met.

    “With these caveats, we are ready for whatever Comet ATLAS has to tell us,” says Daniel Müller, ESA Project Scientist for Solar Orbiter.

    Expect the unexpected

    Hubble captures breakup of Comet ATLAS in April 2020.

    Another challenge entails the comet’s behaviour. Comet ATLAS was discovered on 28 December 2019. During the next few months, it brightened so much that astronomers wondered whether it would become visible to the naked eye in May.

    Unfortunately, in early April the comet fragmented. As a result, its brightness dropped significantly too, robbing sky watchers of the view. A further fragmentation in mid-May has diminished the comet even more, making it less likely to be detectable by Solar Orbiter.

    Although the chances of detection have reduced, the effort is still worth making according to Geraint.

    “With each encounter with a comet, we learn more about these intriguing objects. If Solar Orbiter detects Comet ATLAS’s presence, then we’ll learn more about how comets interact with the solar wind, and we can check, for example, whether our expectations of dust tail behaviour agree with our models,” he explains. “All missions that encounter comets provide pieces of the jigsaw puzzle.”

    Geraint is the principal investigator of ESA’s future Comet Interceptor mission, which consists of three spacecraft and is scheduled for launch in 2028. It will make a much closer flyby of an as yet unknown comet that will be selected from the newly discovered comets nearer the time of launch (or even after that).

    Grazing the Sun

    Solar Orbiter: journey around the Sun.

    Solar Orbiter is currently circling our parent star between the orbits of Venus and Mercury, with its first perihelion to take place on 15 June, around 77 million kilometres from the Sun. In coming years, it will get much closer, within the orbit of Mercury, around 42 million kilometres from the solar surface. Meanwhile, Comet ATLAS is already there, approaching its own perihelion, which is expected on 31 May, around 37 million kilometres from the Sun.

    “This tail crossing is also exciting because it will happen for the first time at such close distances from the Sun, with the comet nucleus being inside the orbit of Mercury,” says Yannis Zouganelis, ESA Deputy Project Scientist for Solar Orbiter.

    Understanding the dust environment in the innermost region of the Solar System is one of Solar Orbiter’s scientific objectives.

    “Near-Sun comets like Comet ATLAS are sources of dust in the inner heliosphere and so this study will not only help us understand the comet, but also the dust environment of our star,” adds Yannis.

    Looking at an icy object rather than the scorching Sun is certainly an exciting – and unexpected – way for Solar Orbiter to start its scientific mission, but that’s the nature of science.

    “Scientific discovery is built on good planning and serendipity. In the three months since launch, the Solar Orbiter team has already proved that it’s ready for both,” says Daniel.

    Science paper:
    Research Notes of the AAS

    See the full article here .

    National Aeronautics and Space Administration(US)/European Space Agency [Agence spatiale européenne] [Europäische Weltraumorganisation] (EU) Hubble Space Telescope

    European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)/National Aeronautics and Space Administration (US) Solar Orbiter

    His lucky encounter has presented researchers with a unique opportunity to investigate the structure of an isolated cometary tail. Using combined measurements from all of Solar Orbiter’s in-situ instruments, the scientists have reconstructed the encounter with ATLAS’s tail. The resulting model indicates that the ambient interplanetary magnetic field carried by the solar wind ‘drapes’ around the comet, and surrounds a central tail region with a weaker magnetic field.

    Comets are typically characterized by two separate tails; one is the well-known bright and curved dust tail, the other – typically fainter – is the ion tail. The ion tail originates from the interaction between the cometary gas and the surrounding solar wind, the hot gas of charged particles that constantly blows from the Sun and permeates the whole Solar System.

    When the solar wind interacts with a solid obstacle, like a comet, its magnetic field is thought to bend and ‘drape’ around it. The simultaneous presence of magnetic field draping and cometary ions released by the melting of the icy nucleus then produces the characteristic second ion tail, which can extend for large distances downstream from the comet’s nucleus.

    Lorenzo Matteini, a solar physicist at Imperial College London and leader of the work, says: “This is quite a unique event, and an exciting opportunity for us to study the makeup and structure of comet tails in unprecedented detail. Hopefully with the Parker Solar Probe and Solar Orbiter now orbiting the Sun closer than ever before, these events may become much more common in future!”

    NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker.

    This is the first comet tail detection occurring so close to the Sun – well inside the orbit of Venus. It is also one of the very few cases where scientists have been able to make direct measurements from a fragmented comet. Data from this encounter is expected to contribute greatly to our understanding of the interaction of comets with the solar wind and the structure and formation of their ion tails.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition


    The Royal Astronomical Society is a learned society and charity that encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. Its headquarters are in Burlington House, on Piccadilly in London. The society has over 4,000 members (“Fellows”), most of them professional researchers or postgraduate students. Around a quarter of Fellows live outside the UK.

    The society holds monthly scientific meetings in London, and the annual National Astronomy Meeting at varying locations in the British Isles. The Royal Astronomical Society publishes the scientific journals MNRAS and Geophysical Journal International, along with the trade magazine Astronomy & Geophysics.

    The Royal Astronomical Society maintains an astronomy research library, engages in public outreach and advises the UK government on astronomy education. The society recognises achievement in Astronomy and Geophysics by issuing annual awards and prizes, with its highest award being the Gold Medal of the Royal Astronomical Society. The RAS is the UK adhering organisation to the International Astronomical Union and a member of the UK Science Council.

    The society was founded in 1820 as the Astronomical Society of London to support astronomical research. At that time, most members were ‘gentleman astronomers’ rather than professionals. It became the Royal Astronomical Society in 1831 on receiving a Royal Charter from William IV. A Supplemental Charter in 1915 opened up the fellowship to women.

    Associated groups

    The RAS sponsors topical groups, many of them in interdisciplinary areas where the group is jointly sponsored by another learned society or professional body:

    The Astrobiology Society of Britain (with the NASA Astrobiology Institute)
    The Astroparticle Physics Group (with the Institute of Physics)
    The Astrophysical Chemistry Group (with the Royal Society of Chemistry)
    The British Geophysical Association (with the Geological Society of London)
    The Magnetosphere Ionosphere and Solar-Terrestrial group (generally known by the acronym MIST)
    The UK Planetary Forum
    The UK Solar Physics group

  • richardmitnick 4:57 pm on June 24, 2021 Permalink | Reply
    Tags: "Arctic Circle is already recording 118 F degree days (and summer is just heating up)", , ESA's Copernicus Sentinal-3A and 3B satellites, European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU), , , On the summer solstice (June 20 — the longest day of the year) two ESA satellites recorded a scorching temperature of 118 degrees Fahrenheit (48 degrees Celsius ) on the ground in Arctic Siberia.   

    From Live Science : “Arctic Circle is already recording 118 F degree days (and summer is just heating up)” 

    From Live Science

    Brandon Specktor

    On the same day last year, air temperatures in the area blazed past 100 degrees F for the first time in recorded history.

    Land temperatures in Siberia exceeded 118 degrees Fahrenheit on the first day of summer. (Image credit: European Union, European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) Copernicus Sentinel-3 imagery.

    ESA – Copernicus Sentinel-3.

    On the summer solstice (June 20 — the longest day of the year) two ESA satellites recorded a scorching temperature of 118 degrees Fahrenheit (48 degrees Celsius ) on the ground in Arctic Siberia.

    This isn’t quite a new heat record; as a post on the ESA’s Copernicus satellite website noted, this egg-boiling temperature was detected only on the ground in Siberia’s Sakha Republic, while the region’s air temperature (the temperature people would actually feel while walking around) was a toasty 86 F (30 C).

    However, that’s still an anomalously high temperature for the Arctic Circle — and one that could exacerbate the region’s melting permafrost, which is the only thing preventing ancient caches of greenhouse gases from reentering Earth’s atmosphere, according to Gizmodo.

    The ESA’s Copernicus Sentinal-3A and 3B satellites recorded the high temperatures in the midst of an ongoing heat wave over much of Siberia. The heat spike is, unfortunately, a predictable start to summer, following a spring that saw hundreds of wildfires scorching the Siberian countryside and blacking out major cities with blankets of smoke.

    Many of these spring fires were “zombie fires,” so named because they are thought to be the rekindled remains of wildfires that ignited the previous summer and were never fully extinguished. The zombie fires smoldered for months under winter ice and snow, fed by the carbon-rich peat below the surface. When the spring melt arrived, the old fires blazed anew, Live Science previously reported.

    If last summer is any indication, the hot solstice temperatures are just the beginning. Precisely one year ago, on June 20, 2020, the same region of Siberia recorded the first 100 F (38 C) day above the Arctic Circle — the hottest temperature ever recorded there. The sweltering day in Siberia fits into a larger climate change trend. For years, average temperatures in the Arctic have been rising at a far faster rate than anywhere else on Earth, largely due to melting sea ice induced by man-made global warming.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

  • richardmitnick 1:23 pm on April 23, 2021 Permalink | Reply
    Tags: "Astronomers Release New All-Sky Map of Milky Way's Outer Reaches", Although there are multiple theories about the nature of dark matter all of them indicate that it should be present in the Milky Way’s halo., , , , European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU), , , , The data for the new map comes from ESA’s Gaia mission and NASA’s Near Earth Object Wide Field Infrared Survey Explorer-or NEOWISE-which operated from 2009 to 2013 under the moniker WISE., The highlight of the new chart is a wake of stars stirred up by a small galaxy set to collide with the Milky Way. The map could also offer a new test of dark matter theories., The interaction between the dark matter and the Large Magellanic Cloud has big implications for our galaxy., The LMC is located about 160000 light-years from Earth and is less than one-quarter the mass of the Milky Way., The new map reveals how a small galaxy called the Large Magellanic Cloud (LMC) has sailed through the Milky Way’s galactic halo like a ship through water.   

    From NASA JPL-Caltech : “Astronomers Release New All-Sky Map of Milky Way’s Outer Reaches” 

    NASA JPL Banner

    From NASA JPL-Caltech

    Apr 21, 2021

    Calla Cofield
    Jet Propulsion Laboratory, Pasadena, Calif.

    The highlight of the new chart is a wake of stars stirred up by a small galaxy set to collide with the Milky Way. The map could also offer a new test of dark matter theories.

    Astronomers using data from National Aeronautics Space Agency (US) and European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) telescopes have released a new all-sky map of the outermost region of our galaxy. Known as the galactic halo, this area lies outside the swirling spiral arms that form the Milky Way’s recognizable central disk and is sparsely populated with stars.

    Images of the Milky Way and the Large Magellanic Cloud (LMC) are overlaid on a map of the surrounding galactic halo. The smaller structure is a wake created by the LMC’s motion through this region. The larger light-blue feature corresponds to a high density of stars observed in the northern hemisphere of our galaxy. Credit: NASA/ESA/JPL-Caltech/Conroy et. al. 2021

    Though the halo may appear mostly empty, it is also predicted to contain a massive reservoir of Dark Matter, a mysterious and invisible substance thought to make up the bulk of all the mass in the universe.

    The data for the new map comes from ESA’s Gaia mission and NASA’s Near Earth Object Wide Field Infrared Survey Explorer-or NEOWISE-which operated from 2009 to 2013 under the moniker WISE.

    The study makes use of data collected by the spacecraft between 2009 and 2018.

    The new map reveals how a small galaxy called the Large Magellanic Cloud (LMC) – so named because it is the larger of two dwarf galaxies orbiting the Milky Way – has sailed through the Milky Way’s galactic halo like a ship through water-its gravity creating a wake in the stars behind it.

    The LMC is located about 160000 light-years from Earth and is less than one-quarter the mass of the Milky Way.

    A simulation of dark matter surrounding the Milky Way galaxy (small ring at center) and the Large Magellanic Cloud (LMC) reveals two areas of high density: the smaller of the two light blue areas is a wake created by the LMC’s motion through this region. The larger corresponds to an excess of stars in the Milky Way’s northern hemisphere. Credit: NASA/JPL-Caltech/National Science Foundation (US)/R. Hurt/N. Garavito-Camargo & G. Besla.

    Though the inner portions of the halo have been mapped with a high level of accuracy, this is the first map to provide a similar picture of the halo’s outer regions, where the wake is found – about 200,000 light-years to 325,000 light-years from the galactic center. Previous studies have hinted at the wake’s existence, but the all-sky map confirms its presence and offers a detailed view of its shape, size, and location.

    This disturbance in the halo also provides astronomers with an opportunity to study something they can’t observe directly: dark matter. While it doesn’t emit, reflect, or absorb light, the gravitational influence of dark matter has been observed across the universe. It is thought to create a scaffolding on which galaxies are built, such that without it, galaxies would fly apart as they spin. Dark matter is estimated to be five times more common in the universe than all the matter that emits and/or interacts with light, from stars to planets to gas clouds.

    Although there are multiple theories about the nature of dark matter all of them indicate that it should be present in the Milky Way’s halo. If that’s the case, then as the LMC sails through this region, it should leave a wake in the dark matter as well. The wake observed in the new star map is thought to be the outline of this dark matter wake; the stars are like leaves on the surface of this invisible ocean, their position shifting with the dark matter.

    The interaction between the dark matter and the Large Magellanic Cloud has big implications for our galaxy. As the LMC orbits the Milky Way, the dark matter’s gravity drags on the LMC and slows it down. This will cause the dwarf galaxy’s orbit to get smaller and smaller, until the galaxy finally collides with the Milky Way in about 2 billion years. These types of mergers might be a key driver in the growth of massive galaxies across the universe. In fact, astronomers think the Milky Way merged with another small galaxy about 10 billion years ago.

    “This robbing of a smaller galaxy’s energy is not only why the LMC is merging with the Milky Way, but also why all galaxy mergers happen,” said Rohan Naidu, a doctoral student in astronomy at Harvard University (US) and a co-author of the new paper. “The wake in our map is a really neat confirmation that our basic picture for how galaxies merge is on point!”

    A Rare Opportunity

    The authors of the paper also think the new map – along with additional data and theoretical analyses – may provide a test for different theories about the nature of dark matter, such as whether it consists of particles, like regular matter, and what the properties of those particles are.

    “You can imagine that the wake behind a boat will be different if the boat is sailing through water or through honey,” said Charlie Conroy, a professor at Harvard University and an astronomer at the Harvard Smithsonian Center for Astrophysics (US), who coauthored the study. “In this case, the properties of the wake are determined by which dark matter theory we apply.”

    Conroy led the team that mapped the positions of over 1,300 stars in the halo. The challenge arose in trying to measure the exact distance from Earth to a large portion of those stars: It’s often impossible to figure out whether a star is faint and close by or bright and far away. The team used data from ESA’s Gaia mission, which provides the location of many stars in the sky but cannot measure distances to the stars in the Milky Way’s outer regions.

    After identifying stars most likely located in the halo (because they were not obviously inside our galaxy or the LMC), the team looked for stars belonging to a class of giant stars with a specific light “signature” detectable by NEOWISE. Knowing the basic properties of the selected stars enabled the team to figure out their distance from Earth and create the new map. It charts a region starting about 200,000 light-years from the Milky Way’s center, or about where the LMC’s wake was predicted to begin, and extends about 125,000 light-years beyond that.

    Conroy and his colleagues were inspired to hunt for LMC’s wake after learning about a team of astrophysicists at the University of Arizona (US) that makes computer models predicting what dark matter in the galactic halo should look like. The two groups worked together on the new study.

    One model by the Arizona team, included in the new study, predicted the general structure and specific location of the star wake revealed in the new map. Once the data had confirmed that the model was correct, the team could confirm what other investigations have also hinted at: that the LMC is likely on its first orbit around the Milky Way. If the smaller galaxy had already made multiple orbits, the shape and location of the wake would be significantly different from what has been observed. Astronomers think the LMC formed in the same environment as the Milky Way and another nearby galaxy, Messier 31, and that it is close to completing a long first orbit around our galaxy (about 13 billion years). Its next orbit will be much shorter due to its interaction with the Milky Way.

    “Confirming our theoretical prediction with observational data tells us that our understanding of the interaction between these two galaxies, including the dark matter, is on the right track,” said University of Arizona doctoral student in astronomy Nicolás Garavito-Camargo, who led work on the model used in the paper.

    The new map also provides astronomers with a rare opportunity to test the properties of the dark matter (the notional water or honey) in our own galaxy. In the new study, Garavito-Camargo and colleagues used a popular dark matter theory called cold dark matter that fits the observed star map relatively well.

    Now the University of Arizona team is running simulations that use different dark matter theories to see which one best matches the wake observed in the stars.

    “It’s a really special set of circumstances that came together to create this scenario that lets us test our dark matter theories,” said Gurtina Besla, a co-author of the study and an associate professor at the University of Arizona. “But we can only realize that test with the combination of this new map and the dark matter simulations that we built.”

    Launched in 2009, the WISE spacecraft was placed into hibernation in 2011 after completing its primary mission. In September 2013, NASA reactivated the spacecraft with the primary goal of scanning for near-Earth objects, or NEOs, and the mission and spacecraft were renamed NEOWISE. NASA’s Jet Propulsion Laboratory in Southern California managed and operated WISE for NASA’s Science Mission Directorate. The mission was selected competitively under NASA’s Explorers Program managed by the agency’s Goddard Space Flight Center (US). NEOWISE is a project of JPL, a division of California Institute of Technology (US), and the University of Arizona, supported by NASA’s Planetary Defense Coordination Office.

    Science paper:
    All-sky dynamical response of the Galactic halo to the Large Magellanic Cloud

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    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, 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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