The SOCIETY for POPULAR ASTRONOMY Electronic News Bulletin No. 446 June 18th

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    The SOCIETY for POPULAR ASTRONOMY Electronic News Bulletin No. 446 2017 June 18

    Here is the latest round-up of news from the Society for Popular
    Astronomy. The SPA is arguably Britain's liveliest astronomical
    society, with members all over the world. We accept subscription
    payments online at our secure site and can take credit and debit
    cards. You can join or renew via a secure server or just see how
    much we have to offer by visiting http://www.popastro.com/

    ASTEROID-HUNTING SPACECRAFT SUCCESS
    NASA

    The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE)
    mission has released its third year of survey data, with the space-
    craft discovering 97 previously unknown celestial objects in the
    last year. Of those, 28 were near-Earth objects, 64 were main-belt
    asteroids, and five were comets. The spacecraft has now characterized
    a total of 693 near-Earth objects since the mission was re-started in
    2013 December. Of those, 114 are new. NEOWISE is not only discovering
    previously uncharted asteroids and comets, but it is providing
    excellent data on many of those already known. Near-Earth objects
    (NEOs) are comets and asteroids that have been nudged by the
    gravitational attraction of the planets in the Solar System into
    orbits that cause them to enter the Earth's neighbourhood. Ten of the
    objects discovered by NEOWISE in the past year have been classified as
    potentially hazardous asteroids, on the basis of their sizes and orbits.
    More than 2.6 million infrared images of the sky were collected in the
    third year of operations by NEOWISE. Those data are combined with the
    first two years' NEOWISE data into a single archive that contains
    approximately 7.7 million sets of images and a data base of more than
    57.7 (US-)billion source detections extracted from those images. The
    NEOWISE images also contain glimpses of rare objects, like comet
    C/2010 L5 WISE. A new technique of modelling comet behaviour, called
    tail-fitting, showed that that particular comet experienced a brief
    outburst as it swept through the inner Solar System. The tail-
    fitting technique identifies the size and quantity of dust particles
    in the vicinity of the comet, and when they were ejected from the
    comet's nucleus, revealing the history of the comet's activity. With
    tail-fitting, future all-sky surveys may be able to find and collect
    data on more cometary-outburst activity when it happens.
    Originally called the Wide-field Infrared Survey Explorer (WISE), the
    spacecraft was launched in 2009 December. It was placed in hiber-
    nation in 2011 after its primary astrophysical mission was completed.
    In 2013 September it was re-activated, re-named NEOWISE and assigned
    a new mission: to assist NASA's efforts to identify the population of
    potentially hazardous near-Earth objects. NEOWISE is also character-
    izing more distant populations of asteroids and comets to provide
    information about their sizes and compositions.

    ENCELADUS MAY HAVE TIPPED OVER
    NASA

    Saturn's icy, ocean-bearing moon Enceladus may have tipped over in the
    distant past, according to recent research from the Cassini mission.
    Researchers found evidence that the moon's spin axis — the line
    through the north and south poles — has re-oriented, possibly owing
    to a collision with a smaller body, such as an asteroid. Examining
    the moon's features, the team showed that Enceladus appears to have
    tipped away from its original axis by about 55 degrees — more than
    halfway toward rolling completely onto its side. Cassini found a
    chain of low areas, or basins, that trace a belt across the moon's
    surface that researchers believe are the fossil remnants of an earlier
    equator and poles. The area around the icy moon's current south pole
    is an active region where long, linear fractures referred to as 'tiger
    stripes' slice across the surface. Scientists speculate that an
    asteroid may have struck the region in the past when it was closer to
    the equator.

    In 2005, Cassini discovered that jets of water vapour and icy
    particles spray from the tiger-stripe fractures — evidence that an
    underground ocean is venting directly into space from beneath the
    active south-polar surface. Whether it was caused by an impact or
    some other process, astronomers think that the disruption and creation
    of the tiger-stripe landform caused some of Enceladus' mass to be
    redistributed, making the moon's rotation unsteady and wobbly. The
    rotation would eventually have stabilized, probably taking more than a
    million years to do so. By the time that the rotation settled down,
    the north-south axis would have re-oriented to pass through different
    points on the surface — a mechanism researchers call 'true polar
    wander'. The polar-wander idea could explain why Enceladus' modern-
    day north and south poles appear quite different. The south is active
    and topographically young, while the north is covered in craters and
    appears much older. The moon's original poles would have looked more
    alike before the event that caused Enceladus to tip over and relocate
    the disrupted tiger-stripe landform to the moon's south-polar region.

    INGREDIENT OF LIFE FOUND AROUND SUN-LIKE STARS
    RAS

    Using the Atacama Large Millimetre / submillimetre Array (ALMA),
    astronomers have observed stars like the Sun at very early stages in
    their formation and found traces of methyl isocyanate — a chemical
    building-block of life. This is the first-ever detection of that
    pre-biotic molecule towards solar-type proto-stars, the sort from
    which our Solar System evolved. The discovery could help scientists
    understand how life arose on Earth. Two teams of astronomers detected
    the methyl isocyanate in the multiple-star system IRAS 16293-2422.
    ALMA's capabilities allowed both teams to observe the molecule at
    several different and characteristic wavelengths across the radio
    spectrum. They found the unique chemical fingerprints located in the
    warm, dense inner regions of the cocoon of dust and gas surrounding
    young stars in their earliest stages of evolution. Each team
    identified and isolated the signatures of methyl isocyanate. They
    followed that up with computer chemical modelling and laboratory
    experiments to refine their understanding of the molecule's origin.
    IRAS 16293-2422 is a multiple system of very young stars, around 400
    light-years away, in a large star-forming region called Rho Ophiuchi.
    The new results from ALMA show that methyl isocyanate gas surrounds
    each of the young stars. The Earth and the other planets in the Solar
    System formed from the material left over after the formation of the
    Sun. Studying solar-type proto-stars can therefore open a window to
    the past for astronomers and allow them to observe conditions similar
    to those that led to the formation of our Solar System over 4.5 billion years
    ago.

    COLLAPSING STAR GIVES BIRTH TO BLACK HOLE
    NASA

    Astronomers used the combined power of the Large Binocular Telescope
    (LBT) and the Hubble and Spitzer space telescopes, to look for
    remnants of a vanished star, only to find that it disappeared out of
    sight. The star, which was 25 times the mass of the Sun, should have
    exploded in a very bright supernova. Instead, it fizzled out — and
    then left behind a black hole. 'Massive fails', like that one in a
    'nearby' galaxy, could explain why astronomers rarely see supernovae
    from the most massive stars. As many as 30% of such stars, it seems,
    may quietly collapse into black holes — no supernova required. The
    typical view is that a star can form a black hole only after it goes
    supernova. If a star can fall short of a supernova and still make a
    black hole, that would help to explain why we don't see supernovae
    from the most massive stars. Among the galaxies that have been
    watched is NGC 6946, a spiral galaxy 22 million light-years away that
    is nicknamed the 'Fireworks Galaxy' because supernovae frequently
    happen there — indeed, one, SN 2017eaw, was discovered as recently as
    May 14. Starting in 2009, one particular star, named N6946-BH1, began
    to brighten weakly. By 2015, it appeared to have winked out of
    existence. After the LBT survey for failed supernovae turned up the
    star, astronomers aimed the Hubble and Spitzer space telescopes to see
    if it was still there but merely dimmed. They also used Spitzer to
    search for any infrared radiation emanating from the spot. That would
    have been a sign that the star was still present, but perhaps just
    hidden behind a dust cloud. All the tests came up negative. The star
    was no longer there. By a process of elimination, the researchers
    eventually concluded that the star must have become a black hole. It
    is too early in the project to know how often stars experience massive
    failures, but astronomers are able to make a preliminary estimate.
    N6946-BH1 is the only probable failed supernova found in the first
    seven years of the survey. During that time, six normal supernovae
    have occurred within the galaxies monitored, suggesting that 10 to 30
    per cent of massive stars die as failed supernovae. That is just the
    fraction that would explain the very problem that motivated the
    observers to start the survey, that is, that there are fewer observed
    supernovae than should be occurring if all massive stars die that way.
    The really interesting part of the discovery is the implications that
    it holds for the origins of very massive black holes — the kind that
    the LIGO experiment* detected via gravitational waves. It does not
    necessarily make sense that a massive star could become a supernova
    — a process which entails blowing off much of its outer layers — and
    still have enough mass left over to form a massive black hole on the
    scale of those that LIGO detected. It may be much easier to under-
    stand how a very massive black hole is made if there is no supernova.
    *LIGO is the Laser Interferometer Gravitational-Wave Observatory.

    GALAXY ALIGNMENTS TRACED BACK 10 BILLION YEARS
    University of Turku

    A new study reveals that the most massive galaxies in the Universe
    have been aligned with their surroundings for at least ten billion years.
    That discovery shows that galaxies, like people, are influenced by their
    environment from a young age. Astronomers have long known that
    galaxies cluster together into enormous systems — the urban centres of
    the cosmos — and that the largest galaxies tend to 'point' towards their
    neighbours. But how and when those alignments occur remains a mystery.
    Using the Hubble Space Telescope, the international team of collaborators
    observed 65 distant galaxy clusters whose light has taken billions of years to
    reach the Earth. They showed for the first time that the largest galaxies in these systems
    were already aligned with their surroundings when the Universe was
    only 1/3 of its current age. Although clusters have hundreds or
    thousands of member galaxies, most are randomly oriented in space.
    Only the biggest galaxies are aligned with their surroundings, which
    suggests that they are especially sensitive to their environment.
    The team is eager to look further back in time by observing more
    remote clusters, but studying galaxies at the dawn of time is not
    easy, even with Hubble.

    CONTRACTS FOR THE ELT'S GIANT MIRROR SIGNED
    ESO

    Contracts for the manufacture of the 39-metre primary mirror of ESO's
    Extremely Large Telescope have been signed at the ESO headquarters
    near Munich. The German company SCHOTT will produce the blanks of
    the mirror segments, and the French company Safran Reosc will polish,
    mount and test the segments. The contract to polish the mirror blanks
    is the second-largest contract for the ELT construction and the third-
    largest contract ESO has ever awarded. The unique optical system of
    the Extremely Large Telescope consists of five mirrors, each of which
    presents its own significant engineering challenge. The 39-metre-
    diameter primary mirror, which will be made up of 798 individual
    hexagonal segments each measuring 1.4 metres across, will be by far
    the largest ever made for an optical telescope. Together, the
    segments will collect tens of millions of times as much light as the
    human eye. Once the mirror blanks are ready they will be passed to
    Safran Reosc, who will design the mounting interfaces, polish and
    figure the segments, integrate them into their support systems, and
    perform optical tests before delivery. During the polishing process,
    each segment will be polished until it has no surface irregularity
    greater than about 10 nanometres. Both SCHOTT and Safran Reosc have
    already had long and successful involvements with ESO. Together they
    manufactured many optical components, including the 8.2-metre main
    mirrors of the four Unit Telescopes of the ESO Very Large Telescope.
    The ELT is currently under construction at Cerro Armazones near the
    Paranal Observatory in northern Chile, and is scheduled to see first
    light in 2024.

    Bulletin compiled by Clive Down (c) 2017 The Society for Popular Astronomy
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