THE SOCIETY FOR POPULAR ASTRONOMY Electronic News Bulletin No. 466 2018 April 8

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    THE SOCIETY FOR POPULAR ASTRONOMY Electronic News Bulletin No. 466 2018 April 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
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    InSight — short for Interior Exploration using Seismic Investigations,
    Geodesy and Heat Transport — is a stationary lander scheduled to be
    launched towards Mars as soon as May 5. It will be the first mission ever
    dedicated to Mars' deep interior, and the first NASA mission since the
    Apollo moon landings to place a seismometer on the soil of another planet.
    Scientists hope that by detecting marsquakes and other phenomena inside the
    planet, InSight can enable them to understand how Mars formed. InSight
    carries a suite of sensitive instruments to gather such data; unlike a rover
    mission, they require a spacecraft that sits still and carefully places its
    instruments on the Martian surface. NASA is not the only agency excited
    about the mission. Several European partners contributed instruments, or
    instrument components. For example, France's Centre National d'Etudes
    Spatiales (CNES) led a multinational team that built an ultra-sensitive
    seismometer for detecting marsquakes. The German Aerospace Center (DLR)
    developed a thermal probe that can bury itself up to 5 metres underground
    and measure heat flowing from inside the planet. Looking deep into Mars
    will let scientists understand how different its crust, mantle and core are
    from their counterparts on Earth. In a sense, Mars is the exo-planet next
    door — a nearby example of how gas, dust and heat combine and arrange
    themselves into a planet.


    New research finds that 'Oumuamua, the rocky object identified as the first
    confirmed interstellar asteroid, very likely came from a binary-star system.
    For the new study, astronomers set about testing how efficient binary-star
    systems are at ejecting objects. They also looked at how common such star
    systems are in the Galaxy. They found that rocky objects like 'Oumuamua are
    far more likely to come from binary- than single-star systems. They were
    also able to determine that rocky objects are ejected from binary systems in
    comparable numbers to icy objects. Astronomers claim that it is really odd
    that the first object we would see from outside our system would be an
    asteroid, because a comet would be a lot easier to spot and the Solar System
    ejects many more comets than asteroids. Once they determined that binary
    systems are very efficient at ejecting rocky objects, and that a sufficient
    number of them exists, they were satisfied that 'Oumuamua very likely came
    from a binary system. They also concluded that it probably came from a
    system with a relatively hot, high-mass star, since such a system would have
    a greater number of rocky objects closer in. The team suggests that the
    asteroid was very likely to have been ejected from its binary system some
    time during the formation of planets.
    'Oumuamua, which is Hawaiian for 'scout', was first observed by the
    Haleakala Observatory in Hawaii on 2017 October 19. With a radius of 200
    metres and travelling at 30 kilometres per second, at its closest it was
    about 33 million km from the Earth. When it was first discovered,
    researchers assumed that it was a comet. But it did not show any comet-like
    activity as it neared the Sun, so it seemed that it must be rocky, and it
    was quickly re-classified as an asteroid. Researchers were also fairly sure
    it was from outside the Solar System, on the basis of its trajectory and
    speed. An eccentricity of 1.2 — which classifies its path as an open-ended
    hyperbolic orbit — and such a high speed meant that it was not bound by the
    gravity of the Sun. In fact, 'Oumuamua's orbit has the highest eccentricity
    ever observed in an object passing through the Solar System. Major
    questions about 'Oumuamua remain. For planetary scientists, being able to
    observe such objects may yield important clues about how planet formation
    works in other star systems.

    FECYT – Spanish Foundation for Science and Technology

    About 70,000 years ago, a small reddish star approached the Solar System and
    gravitationally disturbed comets and asteroids. Astronomers have verified
    that the movement of some of those objects is still marked by that stellar
    encounter. At a time when modern humans were beginning to leave Africa and
    the Neanderthals were living on our planet, Scholz's star — named after the
    German astronomer who discovered it — approached within less than a light-
    year from the Sun. Nowadays it is almost 20 light-years away, but 70,000
    years ago it entered the Oort cloud, a reservoir of trans-Neptunian objects
    located in the confines of the Solar System. Now astronomers have analyzed
    for the first time the nearly 340 objects of the Solar System with hyper-
    bolic orbits, and in doing so they have detected that the trajectories of
    some of them are influenced by the passage of Scholz's star. Using numerical
    simulations they calculated the radiants or positions in the sky from which
    all these hyperbolic objects seem to come. In principle, one would expect
    such positions to be evenly distributed in the sky, particularly if the
    objects come from the Oort cloud; however, what is found is very different:
    a statistically significant accumulation of radiants. The pronounced over-
    density appears projected in the direction of the constellation of Gemini,
    which fits the close encounter with Scholz's star.
    The time at which that star passed close to us and its position during
    prehistory coincide with the data of the new investigation. It could be a
    coincidence, but it is unlikely that both location and time would be
    compatible just by coincidence. The simulations suggest that Scholz's star
    approached even closer than the 0.6 light-years pointed out in a 2015 study
    as the lower limit. The close fly-by of the star 70,000 years ago did not
    disturb all the hyperbolic objects of the Solar System, only those that were
    closest to it at that time. For example, the radiant of the interstellar
    asteroid `Oumuamua is in the constellation Lyra, very far from Gemini, so it
    is not part of the detected over-density. Scholz's star is actually a
    binary system formed by a small red dwarf, with about 9% of the mass of the
    Sun, around which a still less bright and smaller brown dwarf orbits. Some
    of our distant ancestors may have seen its faint reddish light with their
    naked eyes in the nights of prehistory.


    A team of astronomers found 72 very bright, but quick, events in a recent
    survey, and are still struggling to explain their origin. The scientists
    found the transients in data from the Dark Energy Survey Supernova Programme
    (DES-SN). That is part of a global effort to understand dark energy, an
    entity that seems to be driving an acceleration in the expansion of the
    Universe. DES-SN uses a large camera on the 4-metre telescope at the Cerro
    Tololo Inter-American Observatory (CTIO) in the Chilean Andes. The survey
    looks for supernovae, the explosion of massive stars at the end of their
    lives. A supernova explosion can briefly be as bright as a whole galaxy.
    The team found the largest number of those quick events to date. Even for
    transient phenomena, they are very peculiar: while they have a similar
    maximum brightness to different types of supernovae they are visible for
    shorter times, from a week to a month. In contrast, supernovae last for
    several months or more. The events appear to be both hot, with temperatures
    from 10,000 to 30,000 degrees Celsius, and large, ranging in size from
    several up to a hundred times the distance from the Earth to the Sun. They
    also seem to be expanding and cooling as they evolve in time, as would be
    expected from an exploding event such as a supernova. There is still debate
    on the origin of these transients. One possible scenario is that the star
    sheds a lot of material before a supernova explosion, and in extreme cases
    could be completely enveloped by a shroud of matter. The supernova itself
    may then heat the surrounding material to very high temperatures. In that
    case astronomers see the hot cloud rather than the exploding star itself.
    To confirm any of that, the team will need a lot more data. For the future,
    the team plans to continue its search for transients, and estimate how often
    they occur compared with more 'routine' supernovae.

    University of Notre Dame

    The slow fade of radioactive elements in a supernova allows astrophysicists
    to study them at length. But the Universe is full of flash-in-the-pan
    transient events lasting only a brief time, so quick and hard to study that
    they remain a mystery. Only by increasing the rate at which telescopes
    monitor the sky has it been possible to catch more Fast-Evolving Luminous
    Transients (FELTs) and begin to understand them. According to a new study,
    researchers say that the Kepler space telescope captured one of the fastest
    FELTs to date. The FELT, captured in 2015, rose in brightness over just 2.2
    days and faded completely within 10 days. Most supernovae can take 20 days
    to reach peak brightness and weeks to become undetectable. Researchers
    debated what could be causing these particularly fast events but ultimately
    settled on a simple explanation: the stars 'burp' before exploding and do
    not generate enough radioactive energy to be seen later. As the supernova
    runs into the gas expelled in the burp, astrophysicists observe a flash.
    The supernova then fades beyond their ability to detect it.
    Astronomers conclude that this was a massive star that exploded, but it had
    a mass loss — a wind — that started a couple of years before it exploded.
    A shock ran into that wind after the explosion, and that is what caused the
    big flash. But it turns out to have been a rather weak supernova, so within
    a couple of weeks we did not see the rest of the light. The only visible
    activity was from the quick collision of the gas and the exploding star,
    where some of the kinetic energy was converted into light. One mystery that
    remains is why the 'burp' would happen such a short time before the super-
    nova explosion. Astrophysicists want to know how the outside of the star
    reacts to what is happening deep in the core. While the Kepler telescope
    and its K2 mission is expected to run out of fuel and end in the coming
    months, NASA's Transiting Exoplanet Survey Satellite (TESS) is planned for
    launch following the K2 mission. Data retrieved during the TESS mission
    could also be used to study FELTs.

    NASA/Goddard Space Flight Center

    Astronomers using the Hubble Space Telescope have uncovered an ancient
    'relic galaxy' in our own cosmic backyard. The very rare and odd assemblage
    of stars has remained essentially unchanged for the past 10 billion
    years and provides valuable new insights into the origin and evolution of
    galaxies billions of years ago. The galaxy, NGC 1277, started its life with
    a bang long ago, churning out stars a thousand times faster than happens
    in our own Milky Way today. But it abruptly went quiescent as the early
    stars aged and grew ever redder. Though Hubble has seen such 'red and dead'
    galaxies in the early Universe, one has never been conclusively found
    nearby. While the early galaxies are so distant, they are just red dots in
    Hubble deep-sky images. NGC 1277 offers a unique opportunity to see one up
    'close'. The researchers learned that the relic galaxy has twice as many
    stars as our Milky Way, but physically it is only one quarter the size of
    our galaxy. Essentially, NGC 1277 is in a state of 'arrested development'.
    Perhaps, like all galaxies, it started out as a compact object but failed to
    accrete more material to grow in size to form a pinwheel-shaped galaxy.
    Researchers say that approximately one in 1,000 massive galaxies is expected
    to be a relic galaxy like NGC 1277. They were not surprised to find it, but
    simply consider that it was in the right place at the right time to evolve
    — or rather not evolve — the way it did.
    The telltale sign of the galaxy's state lies in the ancient globular
    clusters of stars that swarm around it. Massive galaxies tend to have both
    metal-poor (appearing blue) and metal-rich (appearing red) globular
    clusters. The red clusters are believed to form as the galaxy forms, while
    the blue clusters are later brought in as smaller satellites are swallowed
    by the central galaxy. However, NGC 1277 is almost entirely lacking in blue
    globular clusters. The red clusters are the strongest evidence that the
    galaxy went out of the star-making business long ago. However, the lack of
    blue clusters suggests that NGC 1277 never grew further by accreting
    surrounding galaxies. By contrast, our Milky Way contains approximately 180
    blue and red globular clusters. That is due partly to the fact that our
    Milky Way continues cannibalizing galaxies that come too close by in our
    Local Group of a few dozen small galaxies. It is a markedly different
    environment for NGC 1277. That galaxy lives near the centre of the Perseus
    cluster of over 1,000 galaxies, located 240 million light-years away. But
    NGC 1277 is moving so fast through the cluster, at 2 million miles per hour,
    that it cannot merge with other galaxies to collect stars or pull in gas to
    fuel star formation. In addition, near the galaxy cluster centre, inter-
    galactic gas is so hot that it cannot cool to condense and form stars.
    The team started looking for 'arrested development' galaxies in the Sloan
    Digital Sky Survey and found 50 candidate massive compact galaxies. Using a
    similar technique, but from a different sample, NGC 1277 was identified as
    unique in that it has a central black hole that is much more massive than it
    should be for a galaxy of that size. That reinforces the scenario that the
    supermassive black hole and dense hub of the galaxy grew simultaneously, but
    the galaxy's stellar population stopped growing and expanding because it was
    starved of outside material. The team has 10 other candidate galaxies to
    look at with varying degrees of 'arrested development'.

    University of California – Berkeley

    Thanks to a rare cosmic alignment, astronomers have observed the most
    distant normal star ever observed, some 9 billion light years away.
    While astronomers routinely study galaxies much farther away, they are
    visible only because they glow with the brightness of millions of stars.
    And a supernova, often brighter than the galaxy in which it sits, also can
    be visible across the entire Universe. In galaxies beyond a distance of
    about 100 million light-years, however, the stars are impossible to make out
    individually. But gravitational lensing — the bending of light by massive
    galaxy clusters in the line of sight — can magnify the distant universe and
    make dim and distant objects visible. Typically, lensing magnifies galaxies
    by up to 50 times, but in this case, the star was magnified more than 2,000
    times. It was discovered in Hubble telescope images taken in late April
    2016. The discovery of the star, which astronomers often refer to as Icarus
    rather than by its formal name, MACS J1149 Lensed Star 1 (LS1), initiates a
    new technique for astronomers to study individual stars in galaxies formed
    during the earliest days of the Universe. Such observations can provide a
    rare look at how stars evolve, especially the most luminous ones. The
    astronomy team also used Icarus to test and reject one theory of dark matter
    — that it consists of numerous primordial black holes lurking inside galaxy
    clusters — and to probe the make-up of normal matter and dark matter in the
    galaxy cluster.
    The star was noticed while the observers were monitoring a supernova that
    they had discovered in 2014 while using Hubble to look through a
    gravitational lens in the constellation Leo. That supernova, dubbed
    SN Refsdal in honour of the late Norwegian astrophysicist Sjur Refsdal, a
    pioneer of gravitational lensing studies, was split into four images by the
    lens, a massive galaxy cluster called MACS J1149+2223, located about 5
    billion light years away. Suspecting that Icarus might be more highly
    magnified than SN Refsdal, astronomers analyzed the colours of the light
    coming from it and discovered it was a single star, a blue supergiant. This
    B-type star is much larger, more massive, hotter and possibly hundreds of
    thousands of times intrinsically brighter than the Sun, though still much
    too far away to see without the amplification of gravitational lensing. By
    modelling the lens, they concluded that the tremendous apparent brightening
    of Icarus was probably caused by a unique effect of gravitational lensing.
    While an extended lens, like a galaxy cluster, can only magnify a background
    object up to 50 times, smaller objects can magnify much more. A single star
    in a foreground lens, if precisely aligned with a background star, can
    magnify the background star thousands of times. In this case, a star about
    the size of our Sun briefly passed directly through the line of sight
    between the distant star Icarus and Hubble, boosting its brightness more
    than 2,000 times. In fact, if the alignment was perfect, that single star
    within the cluster turned the light from the distant star into an 'Einstein
    ring' — a halo of light created when light from the distant star bends
    around all sides of the lensing star. The ring is too small to discern from
    this distance, but the effect made the star easily visible by magnifying its
    apparent brightness. The team saw a second star in the Hubble image, which
    could either be a mirror image of Icarus, or a different star being gravi-
    tationally lensed. There are analogous alignments all over the place as
    background stars or stars in lensing galaxies move around, offering the
    possibility of studying very distant stars dating from the early universe,
    just as we have been using gravitational lensing to study distant galaxies.
    For this type of research, nature has provided us with a larger telescope
    than we can possibly build! As for Icarus, the astronomers predict that it
    will be magnified many times over the next decade as cluster stars move
    around, perhaps increasing its brightness as much as 10,000 times.


    Astronomers are back in the dark about what dark matter might be, after new
    observations showed that the mysterious substance may not be interacting
    with forces other than gravity after all. Three years ago, a Durham-led
    international team of researchers thought that they had made a breakthrough
    in ultimately identifying what dark matter is. Observations from the
    Hubble telescope appeared to show that a galaxy in the Abell 3827 cluster —
    approximately 1.3 billion light-years away — had become separated from
    the dark matter surrounding it. Such an offset is predicted during
    collisions if dark matter interacts with forces other than gravity,
    potentially providing clues about what the substance might be. The chance
    orientation at which the Abell 3827 cluster is seen from the Earth makes
    it possible to conduct highly sensitive measurements of its dark matter.
    However, the same group of astronomers now says that new data from more
    recent observations show that dark matter in the Abell 3827 cluster has not
    separated from its galaxy after all. The measurement is consistent with
    dark matter feeling only the force of gravity.

    The Universe is composed of approximately 27 per cent dark matter, with the
    remainder largely consisting of the equally mysterious dark energy. Normal
    matter, such as planets and stars, contributes a relatively small five per
    cent of the Universe. There is believed to be about five times more dark
    matter than all the other particles understood by science, but nobody knows
    what it is. However, dark matter is an essential factor in how the Universe
    looks today, as without the constraining effect of its extra gravity,
    galaxies like our Milky Way would fling themselves apart as they spin. In
    this latest study, the researchers used the Atacama Large Millimetre Array
    (ALMA) in Chile to view the Abell 3827 cluster. ALMA picked up on the
    distorted infra-red light from an unrelated background galaxy, revealing the
    location of the otherwise invisible dark matter that remained unidentified
    in the previous study. While the new results show dark matter staying with
    its galaxy, the researchers said it did not necessarily mean that dark
    matter does not interact. Dark matter might just interact very little, or
    this particular galaxy might be moving directly towards us, so we would not
    expect to see its dark matter displaced sideways, the team added. Several
    new theories of non-standard dark matter have been invented over the past
    two years and many have been simulated at Durham University with high-
    powered computers. With a view to measuring the dark matter in hundreds of
    galaxy clusters and continuing this investigation, Durham University has
    just finished helping to build the new SuperBIT telescope, which gets a
    clear view by rising above the Earth's atmosphere under a giant helium

    Bulletin compiled by Clive Down
    (c) 2018 The Society for Popular Astronomy

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