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  1. #1321
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    Another Popular Astronomy Note. More will follow.

    DAWN MISSION TO CERES EXTENDED
    NASA

    NASA has authorized a second extension of the Dawn mission at Ceres, the
    largest object in the asteroid belt between Mars and Jupiter. During
    this extension, the spacecraft, which has been orbiting Ceres since 2015
    March, will descend to lower altitudes than ever before. The spacecraft
    will continue at Ceres for the remainder of its investigation and will
    remain in a stable orbit indefinitely after its hydrazine fuel runs out.
    The Dawn flight team is studying ways to manoeuvre Dawn into a new
    elliptical orbit, which may take the spacecraft to less than 200 km from
    the surface of Ceres at closest approach. Previously, Dawn's lowest
    altitude was 385 km. A priority of the second Ceres mission extension
    is collecting data with Dawn's gamma-ray and neutron spectrometer,
    which measures the number and energy of gamma rays and neutrons. That
    information is important for understanding the composition of Ceres'
    uppermost layer and how much ice it contains. The spacecraft will also
    take visible-light images of Ceres' surface with its camera, as well as
    measurements of Ceres' mineralogy with its visible and infrared mapping
    spectrometer.

    The extended mission additionally allows Dawn to be in orbit while Ceres
    goes through perihelion, its closest approach to the Sun, which will
    occur in 2018 April. At closer proximity to the Sun, more ice on Ceres'
    surface may turn to water vapour, which may in turn contribute to the
    weak transient atmosphere detected by ESA's Herschel space observatory
    before Dawn's arrival. Building on Dawn's findings, the team has
    hypothesized that water vapour may be produced in part from energetic
    particles from the Sun interacting with ice at shallow depths in Ceres'
    surface. Scientists will combine data from ground-based observatories
    with Dawn's observations to study these phenomena further as Ceres
    approaches perihelion.

  2. #1322
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    Popular Astronomy Note: Electronic News Bulletin No. 456 2017 November 5


    FRESH FINDINGS FROM CASSINI
    NASA

    The Cassini spacecraft ended its journey on Sept. 15 with an intentional
    plunge into the atmosphere of Saturn, but analysis continues on the
    mountain of data the spacecraft sent during its long 'life'. The
    spacecraft's Ion and Neutral Mass Spectrometer (INMS) returned a lot
    of direct measurements of the components in Saturn's upper atmosphere,
    which stretches almost to the rings. From those observations, the team
    sees evidence that molecules from the rings are raining down onto the
    atmosphere. That influx of material from the rings was expected, but
    INMS data show hints of ingredients more complex than just water, which
    makes up the bulk of the rings' composition. In particular, the
    instrument detected methane, a volatile molecule that scientists would
    not expect to be abundant in the rings or found so high in Saturn's
    atmosphere.

    Chief among the questions that scientists hope to answer by using data
    from Cassini is the age and origin of the rings. Theoretical modelling
    has shown that, without forces to confine them, the rings would spread
    out over hundreds of millions of years -- much younger than Saturn
    itself. Such spreading happens because faster-moving particles that
    orbit closer to Saturn occasionally collide with slower particles on
    slightly farther-out orbits. When that happens, some momentum from the
    faster particles is transferred to the slower particles, speeding the
    latter up in their orbit and causing them to move farther out. The
    inverse happens to the faster, inner particles. Previous research had
    shown that gravitational tugs from the moon Mimas are solely responsible
    for halting the outward spread of Saturn's B ring -- that ring's outer
    edge is defined by the dark region known as the Cassini Division. Ring
    scientists had thought that the small moon Janus was responsible for
    confining the outer edge of the A ring, but a new modelling study shows
    that the A ring's outward creep is kept in check by a confederation of
    moons, including Pan, Atlas, Prometheus, Pandora, Janus, Epimetheus and
    Mimas.

  3. #1323
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    Thanks, DW. There are so many new findings. I had to google Ceres and Dawn.

    Ceres:
    https://en.wikipedia.org/wiki/Ceres_(dwarf_planet)


    Dawn:
    (old article)
    http://earthsky.org/space/dawn-at-ce...stery-features
    "You can always find something better than death."
    Jacob and Wilhelm Grimm, The Bremen Town Musicians

  4. #1324
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    The SOCIETY for POPULAR ASTRONOMY

    Electronic News Bulletin No. 456 2017 November 5

    ASTEROID VISITS FROM BEYOND SOLAR SYSTEM
    NASA

    A small, recently discovered asteroid -- or perhaps a comet -- appears
    to have originated from outside the Solar System, coming from somewhere
    else in our Galaxy. If so, it would be the first 'interstellar object'
    to be observed and confirmed by astronomers. The unusual object -- for
    now designated A/2017 U1 -- is less than 400 metres in diameter and is
    moving remarkably fast. Astronomers are using telescopes around the
    world and in space to observe this notable object, in an effort to learn
    about the origin and possibly composition of the object. A/2017 U1 was
    discovered on October 19 by the University of Hawaii's Pan-STARRS 1
    telescope during the course of its nightly search for near-Earth objects.
    Astronomers immediately realized that it was an unusual object. Its
    motion could not be explained as either a normal Solar-System asteroid
    orbit or a comet orbit. Combined data from follow-up images taken at
    the ESA telescope on Tenerife proved that the object came from outside
    the Solar System. It is the most extreme orbit that NASA scientists
    have ever seen. The object is moving extremely fast, and on such a
    trajectory that we can say with confidence that it is on its way out of
    the Solar System and will not come back. The team plotted the object's
    current trajectory and even looked into its future. A/2017 U1 came from
    the direction of the constellation Lyra, cruising through interstellar
    space at a brisk 25.5 km/s.

    The object approached the Solar System from almost directly 'above' the
    ecliptic, the approximate plane in space where the planets and most
    asteroids orbit the Sun, so it did not have close encounters with any
    of the major planets during its plunge toward the Sun. On Sept. 2, the
    small body crossed under the ecliptic plane just inside Mercury's orbit
    and then made its closest approach to the Sun on Sept. 9; answering to
    the Sun's gravity, it made a hairpin turn under our Solar System,
    passing under the Earth's orbit on Oct. 14 at a distance of about 24
    million kilometres -- about 60 times the distance to the Moon. It has
    now shot back up above the plane of the planets and, travelling at
    44 km/s with respect to the Sun, is speeding toward the constellation
    Pegasus. Astronomers have long suspected that such objects should
    exist, because during the process of planet formation a lot of material
    should be ejected from planetary systems. What is surprising is that we
    have never seen interstellar objects pass through before. Since this is
    the first object of its type ever discovered, rules for naming such
    objects will need to be established by the International Astronomical
    Union.

  5. #1325
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    The SOCIETY for POPULAR ASTRONOMY

    Electronic News Bulletin No. 456 2017 November 5
    AMATEUR DETECTS COMET ORBITING DISTANT STAR
    RAS

    A 'citizen scientist' was the first to detect tell-tale signs that a
    comet was orbiting a distant star monitored by the Kepler space
    observatory. The discovery marks the first time that the presence of an
    object as small as a comet has been inferred by observing dips in the
    intensity of light from a star. Such dips usually signal crossings of
    planets or other objects in front of the star, which briefly block a
    small fraction of its light. In this case things were different: the
    researchers were able to pick out the comet's tail, a trail of gas and
    dust, which blocked about 0.1 per cent of the star's light as the comet
    streaked by. The data came from the Kepler space telescope, a stellar
    observatory that was launched in 2009. For four years, the spacecraft
    monitored about 200,000 stars for dips in brightness caused by transit-
    ing exoplanets. To date, the mission has identified and confirmed more
    than 2,400 exoplanets, mostly orbiting stars in the constellation
    Cygnus, with the help of automated algorithms that quickly sift through
    the data, looking for the characteristic dips. The smallest exoplanets
    detected thus far measure about one-third the diameter of the Earth.

    Comets, in comparison, are only the size of a small city at their
    largest, making them much more difficult to detect. But on March 18
    this year Thomas Jacobs, an amateur astronomer who makes it his hobby to
    comb through Kepler's data, was able to pick out several curious light
    patterns amid the noise. Jacobs is part of the 'Planet Hunters'
    citizen-scientist project established by Yale University, which enlists
    amateur astronomers in the search for exoplanets. The idea was that the
    human eye might be able to notice things that a computer would miss.
    Astronomers could name 10 types of objects that those people have found
    in the Kepler data but that algorithms could not find, because of the
    pattern-recognition capability of the human eye. During the search, the
    amateur observed three unusual dips in the light coming from KIC
    3542116, a faint star located 800 light-years away - he flagged the
    events and alerted a professional astronomer with whom he had collab-
    orated in the past to interpret his findings. A further three transits
    were subsequently found. The asymmetry in the light curves resembled
    disintegrating planets, with long trails of debris that would continue
    to block a bit of light as the planet moves away from the star.
    However, such disintegrating planets orbit their star, transiting
    repeatedly. In contrast, no such periodic pattern had been observed in
    the transits identified. The only kind of body that could do the same
    thing and not repeat is one that probably gets destroyed in the end. In
    other words, instead of repeatedly orbiting the star, the objects must
    have transited, then ultimately flown too close to the star, and
    vaporised. The only thing that fits the bill, and has a small enough
    mass to be destroyed, is a comet.

  6. #1326
    On the road, but not! Danik 2016's Avatar
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    Interesting links, DW! Now comes an astronomical crime story!

    The brown dwarf that killed its brother

    "How do you kill a star? Apparently, all it takes is a nearby companion, astronomers have found. After spotting a system consisting of a low-mass white dwarf (a stellar remnant from a star 0.5-8 times the Sun’s mass) and a “failed star” or brown dwarf, a Brazilian team of astronomers determined that the white dwarf was the result of a normal star’s “premature death” brought about by its tiny companion.

    The work, published September 21 in the Monthly Notices of the Royal Astronomical Society, explores a low-mass binary system consisting of a 0.2-0.3-solar-mass white dwarf, and a 34-46-Jupiter-mass brown dwarf. Located in the constellation Perseus, this binary once held a normal, Sun-like star and a small substellar object, perhaps a brown dwarf (depending on its initial mass). But as the normal star began to swell into a red giant , the smaller object was engulfed — and instead of being destroyed, it triggered a massive ejection of material from the red giant that killed it instead."

    http://www.astronomy.com/news/2017/1...-dwarf-brother
    "You can always find something better than death."
    Jacob and Wilhelm Grimm, The Bremen Town Musicians

  7. #1327
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    https://www.universetoday.com/137778...illions-years/
    This is hardly surprising, but I look forward to the more detailed study of Enceladus in the decade or so to come. I won't be around then, but the thought is nice.

  8. #1328
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    I was going to write about this, but Danik beat me to it... Five spaces too short I am told!

  9. #1329
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    Sorry, DW! Anyway, its the dialogue that matters.
    "You can always find something better than death."
    Jacob and Wilhelm Grimm, The Bremen Town Musicians

  10. #1330
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  11. #1331
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  13. #1333
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    "Proxima Centauri, in addition to being the closest star system to our own, is also the home of the closest exoplanet to Earth. The existence of this planet, Proxima b, was first announced in August of 2016 and then confirmed later that month. The news was met with a great deal of excitement, and a fair of skepticism, as numerous studies followed t were dedicated to determining if this planet could in fact be habitable.

    Another important question has been whether or not Proxima Centauri could have any more objects orbiting it. According to a recent study by an international team of astronomers, Proxima Centauri is also home to a belt of cold dust and debris that is similar to the Main Asteroid Belt and Kuiper Belt in our Solar System. The existence of this dusty belt could indicate the presence of more planets in this star system."
    https://www.universetoday.com/137783...-even-planets/

    They are so desperately after habitable planets that they are going to find something soon, which they think habitable. Anyway, I am sorry in advance for whoever is going to undego thr test of living on those celestial bodies. Back after breakfast to read the other links.
    "You can always find something better than death."
    Jacob and Wilhelm Grimm, The Bremen Town Musicians

  14. #1334
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    I am going to try out starting a discussion of what we already know of Enceladus, the icy moon of Saturn, and one of the moons of Jupiter, Europa. I provide some links for discussion: NASA is planning to do a special study of these moon using a new probe, to see if this moon's oceans may contain life, because of the plumes of water breaking through Enceladus' icy surface. The Europa clipper probe is being planned for the 2020s. These links provide some of the background.

    https://www.jpl.nasa.gov/news/news.php?feature=6942
    https://www.nasa.gov/europa
    https://www.nasa.gov/topics/solarsystem/index.html

  15. #1335
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    Great, DW. Before we start the discussion itself I will try to sum up some of the research trends I observed in the links we posted lately in order not to get lost with so many discoveries.

    I have noticed three major trends:
    -The first one is a general exploration of the celestial realm that exists beyond the solar system. Recent expeditions and more powerfull instruments have led to astonishing discoveries.The former all dominating solar system appears now as a small? part of a bigger mostly unknown whole.
    -Another major focus is the interaction between celestial bodies, specially in regard of originating or destructing each other. I think this concern is related to the query how the earth itself was created and how easily it could be destructed by another celestial body.
    -Last but certainly not least there is an intense interest in the study of the constitution of celestial bodies and their atmosphere. The foremost interest is this obsessive search for an habitable planet.
    "You can always find something better than death."
    Jacob and Wilhelm Grimm, The Bremen Town Musicians

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