The SOCIETY for POPULAR ASTRONOMY Electronic News Bulletin No. 437 2017 8th Jan

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    The SOCIETY for POPULAR ASTRONOMY Electronic News Bulletin No. 437 2017 January 8

    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/

    DETECTION OF BORON ON MARS
    Los Alamos National Laboratory

    Data from NASA's Curiosity rover reveal that boron has been identified
    for the first time on the surface of Mars, indicating that groundwater
    offering the potential for long-term habitability existed on Mars in
    the distant past. If the boron that was found in calcium-sulphate
    mineral veins on Mars is analogous to what we see on Earth, it would
    indicate that the groundwater of ancient Mars that formed the veins
    would have been at 0 to 60 degrees Celsius and neutral-to-alkaline pH.
    The temperature, pH, and dissolved mineral content of the groundwater
    could make it habitable. The boron was identified by the rover's
    laser-shooting 'Chemistry and Camera' ('Chem Cam') instrument. Boron
    is associated on Earth with arid sites where much water has evaporated
    away. However, the environmental implications of the boron found by
    Curiosity are still open to debate. Scientists are considering at
    least two possibilities for the source of the boron that ground water
    left in the veins. It could be that the drying out of part of Gale
    lake resulted in a boron-containing deposit in an overlying layer, not
    yet reached by Curiosity. Some of the material from that layer could
    later have been carried by groundwater down into fractures in the
    rocks. Or perhaps changes in the chemistry of clay-bearing deposits
    and groundwater affected how boron was picked up and dropped off
    within the local sediments.
    The discovery of boron is only one of several recent findings related
    to the composition of Martian rocks. Curiosity is climbing a layered
    Martian mountain and finding rock-composition evidence of how ancient
    lakes and wet underground environments changed, thousands of millions
    of years ago, in ways that affected their favourability for microbial
    life. As the rover has progressed uphill, compositions trend toward
    more clay and more boron. Those and other variations can tell us
    about conditions under which sediments were initially deposited and
    about how later groundwater moving through the accumulated layers
    altered and transported ingredients. Groundwater and chemicals
    dissolved in it that appeared later on Mars left their effects most
    clearly in mineral veins that filled cracks in older layered rock.
    But they also affected the composition of the rock matrix surrounding
    the veins, and the fluid was in turn affected by the rock. Whether
    life has ever existed on Mars is still unknown. No compelling
    evidence for it has been found. When Curiosity landed in Mars' Gale
    Crater in 2012 the mission's main goal was to determine whether the
    area ever offered an environment favourable for microbes. Four recent
    drilling sites, from 'Oudam' this past June to 'Sebina' in October,
    are spaced about 25 metres apart in elevation. Their uphill pattern
    allows the scientific team to sample progressively younger layers that
    reveal Mount Sharp's ancient environmental history. Variations in
    those minerals and elements indicate a dynamic system. They interact
    with groundwater as well as surface water. The water influences the
    chemistry of the clays, but the composition of the water also changes.
    We are seeing chemical complexity indicating a long, interactive
    history with the water. The more complicated the chemistry is, the
    better it is for habitability. The boron and clay underline the
    mobility of elements and electrons, and that is good for life.

    WHERE IS THE ICE ON CERES?
    NASA

    At first glance, Ceres, the largest body in the main asteroid belt,
    does not look icy. Images from the Dawn spacecraft have revealed a
    dark, heavily cratered world whose brightest area is made of highly
    reflective salts — not ice. But newly published studies from Dawn
    scientists show two distinct lines of evidence for ice at or near the
    surface. Those studies support the idea that ice separated from rock
    early in Ceres' history, forming an ice-rich crustal layer, and that
    ice has remained near the surface over the history of the Solar
    System. Water ice on other planetary bodies is important because it
    is an essential ingredient for life as we know it. By finding bodies
    that were water-rich in the distant past, we may discover clues as to
    where life may have existed in the early Solar System. Ceres'
    uppermost surface is rich in hydrogen, with higher concentrations at
    mid-to-high latitudes — consistent with broad expanses of water ice.
    On Ceres, ice is not just localized to a few craters. It is every-
    where, and nearer to the surface at higher latitudes. Researchers
    used the GRaND instrument to determine the concentrations of hydrogen,
    iron and potassium in the uppermost metre of Ceres. GRaND measures
    the number and energy of gamma rays and neutrons emanating from Ceres.
    Neutrons are produced as Galactic cosmic rays interact with Ceres'
    surface. Some neutrons get absorbed into the surface, while others
    escape. Since hydrogen slows down neutrons, it is associated with
    fewer neutrons escaping. On Ceres, hydrogen is likely to be in the
    form of frozen water.
    Researchers found that, rather than a solid ice layer, there is likely
    to be a porous mixture of rocky materials in which ice fills the pores.
    The GRaND data show that the mixture is about 10% ice by weight. That
    result confirms predictions made nearly 30 years ago that ice can
    survive for thousands of millions of years just beneath the surface of
    Ceres. The evidence strengthens the case for the presence of near-
    surface ice on other main-belt asteroids. Ceres' brightest area, in
    the northern-hemisphere crater Occator, does not shine because of ice,
    but rather because of highly reflective salts. Occator's central
    bright region, which includes a dome with fractures, has recently been
    named Cerealia Facula. The crater's cluster of less-reflective spots
    to the east of the centre is called Vinalia Faculae.
    Dawn began its 'extended mission' phase last July, and is currently in
    an elliptical orbit more than 7,200 km from Ceres. During the primary
    mission, Dawn orbited and accomplished all of its original objectives
    at Ceres and at the proto-planet Vesta, which the spacecraft visited
    from 2011 July to 2012 September.

    MOST OUTER PLANETS HAVE NEPTUNE MASS
    NASA/Goddard Space Flight Center

    A new statistical study of planets found by a technique called
    gravitational microlensing suggests that Neptune-mass worlds are
    likely to be the most common type of planet to form in the icy outer
    realms of planetary systems. The study provides the first indication
    of the types of planets waiting to be found far from their host stars,
    where scientists suspect planets form most efficiently. Gravitational
    microlensing occurs through the light-bending effects, predicted by
    Einstein's general theory of relativity, of massive objects. It occurs
    when a foreground star, the lens, randomly aligns with a distant
    background star, the source, as seen fromthe Earth. As the lensing
    star drifts along in its orbit around the galaxy, the alignment shifts
    over days to weeks, changing the apparent brightness of the source.
    The precise pattern of the changes offers clues about the nature of
    the lensing star, including any planets it may host. More than 50
    exoplanets have been discovered through microlensing, compared to
    thousands detected by other techniques, such as detecting the motion
    or dimming of a host star caused by the presence of planets. Because
    the necessary alignments between stars are rare and occur randomly,
    astronomers must monitor millions of stars for the tell-tale bright-
    ness changes that signal a microlensing event. However, microlensing
    holds great potential. It can detect planets hundreds of times more
    distant than most other methods, allowing astronomers to investigate a
    broad swath of our Milky Way galaxy. The technique can locate exo-
    planets of smaller masses and at greater distances from their host
    stars, and it is sensitive enough to find planets floating through
    the Galaxy on their own, not bound to stars.
    The Kepler and K2 missions have been extraordinarily successful in
    finding planets that dim their host stars, with more than 2,500
    confirmed discoveries to date. That technique is sensitive to
    close-in planets but not to distant ones. Microlensing surveys are
    complementary, best probing the outer parts of planetary systems with
    less sensitivity to planets closer to their stars. Combining micro-
    lensing with other techniques provides us with a clearer overall
    picture of the planetary content of our Galaxy. From 2007 to 2012,
    the Microlensing Observations in Astrophysics (MOA) group, a
    collaboration between researchers in Japan and New Zealand, issued
    3,300 alerts informing the astronomical community about ongoing
    microlensing events. The team identified 1,474 well-observed
    microlensing events, with 22 displaying clear planetary signals.
    They include four planets that were never previously reported. To
    study the events in greater detail, the team included data from the
    other major microlensing project operating over the same period, the
    Optical Gravitational Lensing Experiment (OGLE), as well as additional
    observations from other projects designed to follow up on MOA and OGLE
    alerts. From that information, the researchers determined the
    frequency of planets as a function of the mass ratio of the planet and
    star and the distance between them. For a typical planet-hosting star
    with about 60% of the Sun's mass, the typical microlensing planet has
    between 10 and 40 times the Earth's mass. For comparison, Neptune in
    our own Solar System has a mass equivalent to 17 Earths. The results
    imply that cold Neptune-mass worlds are likely to be the most common
    types of planets beyond the so-called snow line, the point where water
    remained frozen during planetary formation. In the Solar System, the
    snow line is thought to have been located at about 2.7 times the
    Earth's mean distance from the Sun, placing it in the middle of the
    main asteroid belt today.

    BIRTHPLACES OF MOST CURRENT STARS
    National Radio Astronomy Observatory

    Astronomers have used the Very Large Array (VLA) and the Atacama Large
    Millimetre Array (ALMA) to look at distant galaxies seen as they were
    some 10 thousand million years ago. At that time, the Universe was
    experiencing its peak rate of star formation. Most stars in the
    present Universe were born then. We knew that galaxies in that era
    were forming stars prolifically, but we did not know what those
    galaxies looked like, because they were shrouded in so much dust that
    almost no visible light escaped them. Radio waves, unlike visible
    light, can get through the dust. However, in order to reveal the
    details of such distant — and faint — galaxies, the astronomers had
    to use the most sensitive radio telescopes. The new observations,
    from the VLA and ALMA, have answered long-standing questions about the
    mechanisms that were responsible for the bulk of star formation in
    those galaxies. They found that intense star formation most
    frequently occurred throughout the galaxies, whereas in present-day
    galaxies with similar high star-formation rates it tends to occur in
    much smaller regions. The astronomers used the VLA and ALMA to study
    galaxies in the Hubble Ultra-Deep Field, a small area of sky observed
    since 2003 with the Hubble Space Telescope (HST). The HST made very
    long exposures of the area to detect galaxies in the far-distant
    Universe, and numerous observing programmes with other telescopes have
    followed up on the HST work. The VLA showed where star formation was
    occurring, and ALMA revealed the cold gas that is the fuel for star
    formation.

    SUPERCLUSTER OF GALAXIES NEAR MILKY WAY
    Australian National University

    Astronomers have found one of the Universe's biggest superclusters of
    galaxies near the Milky Way. The Vela supercluster, which had
    previously gone undetected because it was hidden by stars and dust in
    the Milky Way, is a huge mass that influenced the motion of our
    Galaxy. It is one of the biggest concentrations of galaxies in the
    Universe — possibly the biggest in the neighbourhood of our Galaxy,
    but that will need to be confirmed by further study. The gravity of
    the Vela supercluster may explain the difference between the measured
    motion of the Milky Way through space and the motion predicted from
    the distribution of previously mapped galaxies. The team used the
    Anglo-Australian Telescope to measure distances for many galaxies to
    confirm earlier suggestions that Vela is a supercluster. It also
    helped to estimate the supercluster's effect on the motion of the
    Milky Way. The research involved astronomers based in South Africa,
    Australia and Europe. Two new Australian surveys starting in 2017
    will assess the size of the Vela supercluster. The Taipan optical
    survey will measure galaxy distances over a bigger area around Vela,
    while the WALLABY radio survey will be able to see through the densest
    parts of the Milky Way into the supercluster's heart.

    LARGEST DIGITAL SURVEY OF VISIBLE UNIVERSE
    Queen's University Belfast

    The largest-ever digital survey of the visible Universe, mapping
    billions of stars and galaxies, has been publicly released.
    The data have been made available by the international Pan-STARRS
    project, which includes scientists from Queen's University Belfast,
    who have claimed that it will lead to new discoveries about the
    Universe. Astronomers and cosmologists used a 1.8-m telescope at the
    summit of Haleakala, on Maui, Hawaii, to image three-quarters of the
    visible sky repeatedly over four years. The Pan-STARRS1 Surveys
    include 3 billion separate sources, including stars, galaxies, and
    other objects, and are represented by two petabytes of computer data.
    Pan-STARRS is hosted by the University of Hawaii Institute for
    Astronomy, which is releasing the data alongside the Space Telescope
    Science Institute in Baltimore. The international collaboration also
    includes Queen's University Belfast and the Universities of Durham and
    Edinburgh, and is supported by NASA and the NSF. The project has
    found nearby asteroids in our Solar System, and also the most luminous
    distant explosions in the Universe. Pan-STARRS has already made
    discoveries from Near Earth Objects and Kuiper-Belt objects in the
    Solar System to lonely planets between the stars; it has mapped the
    dust in three dimensions in our Galaxy and found new streams of stars;
    and it has found new kinds of exploding stars and distant quasars in
    the early Universe. The roll-out of the survey data is being done in
    two steps. The current release is the 'Static Sky' which provides an
    average value for the position, brightness and colour for objects seen
    in the sky at individual moments in time. In 2017, a second set of
    data will be released including catalogues and images from each of the
    individual snapshots that Pan-STARRS took of a given region of sky.
    The data from the Pan-STARRS1 surveys will be available online at
    panstarrs.stsci.edu .

    Bulletin compiled by Clive Down
    (c) 2017 The Society for Popular Astronomy
    The Society for Popular Astronomy has been helping beginners in
    amateur astronomy — and more experienced observers — for more than
    60 years. If you are not a member, you may be missing something.
    Membership rates are extremely reasonable, starting at just £20 a
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    The best news is that you can join online right now with a credit or
    debit card at our lively web site: http://www.popastro.com

    ________________________________________
    Society for Popular Astronomy

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