SOCIETY for POPULAR ASTRONOMY Bulletin No. 424 2016 June 12th

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    Electronic News Bulletin No. 424 2016 June 12

    Here is the latest round-up of news from the Society for Popular
    Astronomy. The SPA is arguably Britain's liveliest astronomical
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    University of Bern

    Ingredients that were crucial for the origin of life on Earth,
    including phosphorus and the simple amino-acid glycine, which are key
    components of DNA and cell membranes, have been discovered in Comet
    67P/Churyumov-Gerasimenko. The possibility that water and organic
    molecules were brought to the early Earth through impacts of objects
    like asteroids and comets has long been a subject of debate. While
    Rosetta's ROSINA instrument already showed a significant difference in
    composition between the water on Comet 67P and that on Earth, the same
    instrument has now shown that even if comets did not play as big a
    role in delivering water as was once thought, they certainly had the
    potential to deliver the ingredients of life. While more than 140
    different molecules have already been identified in the interstellar
    medium, amino-acids could not be traced. However, hints of the amino-
    acid glycine, a biologically important organic compound commonly found
    in proteins, were found during the Stardust mission that flew by Comet
    Wild 2 in 2004, but terrestrial contamination of the collected dust
    samples during the analysis could not be ruled out. Now, for the
    first time, repeated detections at a comet have been confirmed by
    Rosetta in Comet 67P's fuzzy atmosphere, or coma. The first detection
    was made in 2014 October, while most measurements were taken during
    the perihelion in 2015 August — the closest point to the Sun along
    the comet's orbit, when the outgassing was strongest. This is the
    first unambiguous detection of glycine in the thin atmosphere of a
    Glycine is very hard to detect, owing to its non-reactive nature: it
    sublimates at slightly below 150°C, so little is released as gas from
    the comet's surface or sub-surface owing to the low temperatures
    there. Scientists see a strong correlation of glycine with dust,
    suggesting that it is probably released from the grains' icy mantles
    once they have warmed up in the coma, perhaps together with other
    volatiles. At the same time, the researchers also detected the
    organic molecules methylamine and ethylamine, which are precursors to
    forming glycine. Alone among amino-acids, glycine has been shown to
    be able to form without liquid water. The simultaneous presence of
    methylamine and ethylamine, and the correlation between dust and
    glycine, also hints at how the glycine was formed. Another exciting
    detection that ROSINA has made for the first time at a comet is that
    of phosphorus, an element found in all living organisms and in the
    structural frameworks of DNA and RNA. The multitude of organic
    molecules already identified by ROSINA, now joined by glycine and
    phosphorus, suggests that comets have the potential to deliver
    molecules important for prebiotic chemistry. Demonstrating that
    comets are reservoirs of primitive material in the Solar System, and
    vessels that could have transported vital ingredients to the Earth, is
    one of the goals of the Rosetta mission.


    After 10 years in orbit, the Mars Reconnaissance Orbiter and its six
    instruments are still in excellent order. Scientists using radar data
    from it have found a record of the most recent Martian ice age
    recorded in the planet's north-polar ice cap. The new results agree
    with previous models that indicated that a glacial period ended about
    400,000 years ago, as well as predictions about how much ice would
    have been accumulated at the poles since then. The results help to
    refine models of Mars's past and future climate by allowing scientists
    to determine how ice moves between the poles and mid-latitudes, and in
    what quantities. Mars has bright icy polar caps that are easily seen
    in telescopes on Earth. A seasonal cover of carbon-dioxide ice and
    snow is observed to advance and retreat over the poles during the
    Martian year. During summer time in the planet's north, the remaining
    northern polar cap is all water ice; the southern cap is water ice as
    well, but remains covered by a relatively thin layer of carbon-dioxide
    ice even in southern summertime. But Mars also undergoes variations
    in its tilt and the shape of its orbit over hundreds of thousands of
    years. The changes cause substantial shifts in the planet's climate,
    including ice ages. The Earth has similar, but less variable, phases
    called Milankovitch cycles.
    Scientists use data from MRO's 'Shallow Sub-surface Radar' (SHARAD) to
    produce images called radargrams that are like vertical slices through
    the layers of ice and dust that comprise the Martian polar ice
    deposits. For the new study, researchers analyzed hundreds of such
    images to look for variations in the layer properties. They identified
    in the ice a boundary that extends across the entire north-polar cap.
    Above the boundary the layers accumulated very quickly and uniformly
    in comparison with the layers below them. The layers in the upper few
    hundred metres display features that indicate a period of erosion,
    followed by a period of rapid accumulation that is still occurring
    today. On Earth, ice ages take hold when the polar regions and high
    latitudes become cooler than average for thousands of years, causing
    glaciers to grow towards the mid-latitudes. In contrast, the Martian
    variety occurs when — as a result of the planet's increased tilt —
    its poles become warmer than lower latitudes. During those periods,
    the polar caps retreat and water vapour migrates towards the equator,
    forming ground ice and glaciers at mid-latitudes. As the warm polar
    period ends, polar ice begins accumulating again, while ice is lost
    from mid-latitudes. Such retreat and re-growth of polar ice is
    exactly what researchers see in the record revealed by the SHARAD
    radar images. An increase in polar ice following a mid-latitude ice
    age is also expected from climate models that show how ice moves
    about according to variations in Mars's orbital characteristics,
    especially its tilt. The models indicate that the last Martian ice
    age ended about 400,000 years ago, as the poles began to cool
    relatively to the equator. Models suggest that since then, the polar
    deposits would have thickened by about 300 metres. The upper unit
    reaches a maximum thickness of 320 metres across the polar cap, which
    is equivalent to a 60-centimetre-thick global layer of ice. That is
    much the same as model predictions that were made by other researchers
    in 2003 and 2007.

    Lund University

    Through a computer-simulated study, astronomers at Lund University in
    Sweden have shown that it is highly likely that the so-called Planet 9
    (not Pluto, which is now considered too small to be a proper planet)
    is an exo-planet. The theory is that the Sun, in its youth some 4.5
    billion years ago, stole Planet 9 from its original star. An extra-
    solar planet, or exo-planet, is by definition a planet located outside
    the Solar System. Now it appears that that definition no longer
    holds. Stars are born in clusters and often pass by one another. It
    is during such encounters that a star can 'steal' one or more planets
    from another star. That is probably what happened when the Sun
    captured Planet 9. There is still no image of Planet 9, not even a
    point of light. We do not know if it is made up of rock, ice, or gas.
    All that we think we know is that its mass is probably around ten
    times the mass of the Earth. It would require a lot more research
    before it could be ascertained that Planet 9 is really an exo-planet
    in the Solar System. If it is, it is the only exo-planet that we,
    realistically, would be able to reach with a space probe.

    Rice University

    In contradiction to the long-standing idea that larger planets take
    longer to form, astronomers have announced the discovery of a giant
    planet in close orbit around a star so young that it still retains a
    disc of circumstellar gas and dust. For decades, conventional wisdom
    has held that large Jupiter-mass planets take a minimum of 10 million
    years to form. That has been questioned over the past decade, and
    many new ideas have been offered, but the fact is that we need to
    identify a number of newly formed planets around young stars if we
    hope to understand planet formation. The planet CI Tau b is at least
    eight times larger than Jupiter and orbits a star only 2 million years
    old about 450 light years from us in the constellation Taurus. The
    Earth and the Sun are more than 4000 million years old, and while the
    3,300-plus catalogue of exo-planets includes some older and some
    younger than the Earth, the obstacles to finding planets around newly
    formed stars are varied and daunting. There are few candidate stars
    that are young enough, bright enough to view in sufficient detail with
    existing telescopes, and which still retain the circumstellar discs of
    gas and dust from which planets form. Stars that are so young also
    are often active, with outbursts and dimmings, strong magnetic fields
    and enormous starspots that can make it appear that planets exist
    where they do not. CI Tau b orbits the star CI Tau once every nine
    days. The planet was found by the radial-velocity method, that relies
    on slight variations in the velocity of a star to detect the
    gravitational pull exerted by nearby planets that are too faint to
    observe directly. The discovery resulted from a survey begun in 2004
    of 140 candidate stars in the star-forming region Taurus–Auriga.
    The result demonstrates that a giant planet can form so rapidly that
    the remnant gas and dust from which the young star formed, surrounding
    the system in a disc, is still present. Giant-planet formation in the
    inner part of the disc, where CI Tau b is located, will have a
    profound impact on the region where smaller terrestrial planets are
    also potentially forming. The team observed CI Tau dozens of times
    with several large telescopes. Initial optical radial-velocity data
    from McDonald Observatory confirmed that a planet might be present,
    and the team added photometry measurements in both visible light and
    the infrared to rule out the possibility that the optical signal
    resulted from starspots or another masking phenomenon. The team has
    examined about half of the young stars in the Taurus–Auriga survey
    sample, and the data from several of them suggest that more planets
    may be found. It is hoped that astronomers can find enough of them to
    shed light on some of the nagging questions about planet formation,
    for instance, the 'brown dwarf desert', an unexplained paucity of
    objects that are larger than giant planets but smaller than stars. If
    careful investigation reveals more brown dwarfs in short-period orbits
    around young stars than around older ones, that would support the idea
    that they tend to merge with their central stars within a few million
    years of forming.


    New research has indicated that the number of planets capable of
    harbouring life may be fewer than has been supposed, because their
    atmospheres keep them too hot. When looking for planets that could
    harbour life, scientists look for planets in the 'habitable zones'
    around their stars — at the right distance from the stars to allow
    water to exist in liquid form. Traditionally, the search has focussed
    on looking for planets orbiting stars like our Sun, such as the Earth.
    However, recent research has turned to small planets orbiting very
    close to M-type dwarfs, which are much smaller and dimmer than the
    Sun. M dwarfs make up around 75% of all the stars in the Galaxy, and
    recent discoveries have suggested that many of them host planets,
    pushing the number of potentially habitable planets into the billions.
    Last month, both the TRAPPIST and Kepler planet-hunting
    telescopes announced the discovery of multiple near-Earth-sized
    planets orbiting M-dwarf stars, some within the habitable zones. The
    new research, from Imperial College London and the Institute for
    Advanced Studies in Princeton, has found that, although they orbit
    smaller and dimmer stars, many of the planets might still be too hot
    to be habitable. The scientists suggest that some of the planets
    might still be habitable, but only those with a smaller mass than the
    Earth, comparable to Venus or Mars. It was previously assumed that
    planets with masses similar to the Earth's would be habitable simply
    because they were in the 'habitable zone'. However, when it was
    considered how such planets evolve over billions of years, that
    assumption was recognized not to be true. It was already known that
    many of the planets are born with thick atmospheres of hydrogen and
    helium, making up roughly 1% of the total planetary mass. In
    comparison, the Earth's atmosphere makes up only a millionth of its
    The greenhouse effect of such a thick atmosphere would make the
    surface far too hot for water to exist as a liquid, rendering the
    planets initially uninhabitable. However, it was thought that over
    time, the strong X-ray and ultraviolet radiation from the parent M-
    dwarf star would evaporate away most of the atmosphere, eventually
    making the planets potentially habitable. The new analysis reveals
    that that is not so. Instead, simulations show that thick hydrogen
    and helium envelopes cannot escape the gravity of planets that are
    similar to or more massive than the Earth, so many of them are likely
    to retain their stifling atmospheres. However, all is not lost,
    according to the researchers. While most of the M-dwarf planets that
    are Earth-mass or more would retain thick atmospheres, smaller
    planets, comparable to Mars, could still lose them to evaporation.
    There are hints from recent exo-planet discoveries that relatively
    puny planets may be even more common around red dwarfs than Earth-
    mass or larger ones, in which case there may indeed be a bonanza of
    potentially habitable planets around cool red stars. Ongoing ground
    and space-based searches, and new space missions to be launched in the
    near future, should provide a definite answer to that question, as
    well as to other questions about the potential suitability of such
    planets for life.

    ESA/Hubble Information Centre

    Astrophysicists have taken a major step forward in understanding how
    super-massive black holes formed. Using data from Hubble and two
    other space telescopes, Italian researchers have found the best
    evidence yet for the seeds that ultimately grow into those cosmic
    giants. For years astronomers have debated how the earliest
    generation of super-massive black holes managed to form very quickly,
    relatively speaking, after the Big Bang. Now, an Italian team has
    identified two objects in the early Universe that seem to be the
    origin of the early super-massive black holes. The two objects
    represent the most promising black-hole seed candidates found so far.
    The group used computer models and applied a new analysis method to
    data from the Chandra X-ray observatory, the Hubble telescope and the
    Spitzer space telescope to find the two objects. Both of them are
    seen less than a billion years after the Big Bang and have an
    initial mass of about 100,000 times that of the Sun. That new result
    helps to explain why we see super-massive black holes less than a
    billion years after the Big Bang.
    There are two main theories to explain the formation of super-massive
    black holes in the early Universe. One assumes that the seeds grow
    out of black holes with masses of about ten to a hundred solar masses,
    as expected for the collapse of a massive star. The black-hole seeds
    then grow through mergers with other small black holes and by pulling
    in gas from their surroundings. However, they would have to grow at a
    remarkably high rate to reach the masses of super-massive black holes
    already discovered to have formed in the first billion years of the
    Universe. The new findings support another scenario where at least
    some very massive black-hole seeds with 100,000 times the mass of the
    Sun formed directly when a massive cloud of gas collapsed. In that
    case the growth of the black holes would be jump-started, and would
    proceed more quickly. Black-hole seeds are extremely hard to find,
    and confirming their detection is very difficult. Even though both
    black-hole seed candidates match the theoretical predictions, further
    observations are needed to confirm their true nature. To distinguish
    properly between the two formation theories, it will also be necessary
    to find more candidates. The team plans to conduct follow-up
    observations in X-rays and in the infrared range to check whether the
    two objects have more of the properties expected for black-hole seeds.
    Upcoming observatories, such as the James Webb space telescope and the
    E-ELT, may be hoped to make a breakthrough in this field, by detecting
    even smaller and more distant black holes.


    A team of astronomers has found an Einstein Ring, a rare image of a
    distant galaxy lensed by gravity. In his General Theory of Relativity
    published a century ago, Albert Einstein predicted that gravity would
    distort the fabric of space-time, and that light would follow curved
    paths as a result. Astronomers first observed that effect in 1919, by
    measuring the positions of stars seen near the Sun during the total
    solar eclipse of that year, and finding the predicted small shift
    caused by the gravitational field. On a larger scale, light from
    distant galaxies is bent by black holes and massive galaxies that lie
    between them and the Earth. The intervening objects act as lenses,
    creating arcs and 'Einstein rings' of light. The rings are
    comparatively rare and usually appear as small features in the sky.
    That makes them hard to see clearly, and most are observed with radio
    telescopes, or with the Hubble telescope. Their rarity derives from
    the huge distances involved, and the low probability of our Galaxy,
    the lens galaxy and the distant galaxy being almost exactly in line.

    The newly discovered ring lies in the direction of the constellation
    Sculptor in the southern sky. It was found in archived images from
    the Dark Energy Camera mounted on the Blanco 4-m telescope at CTIO in
    Chile. The team named the ring 'Canarias', in homage to the work
    carried out by astronomers on La Palma and Tenerife. Light arriving
    at the Earth today left the Einstein ring 8 billion years ago, so we
    see the ring as it was 5 billion years after the Big Bang. Despite
    its small apparent size (4.5 arcseconds), it is larger than most of
    the other rings found to date. Follow-up observations with the 10.4-m
    Gran Telescopio Canarias confirms its distance and shows that the
    intervening lens galaxy has a mass equivalent to about a million
    million Suns.


    Dark matter is a mysterious substance composing most of the material
    Universe, now widely thought to be some form of massive exotic
    particle. An intriguing alternative view is that dark matter is made
    of black holes formed during the first second of the Universe's
    existence, known as primordial black holes. Now a scientist suggests
    that that interpretation aligns with our knowledge of cosmic infrared
    and X-ray background glows and may explain the unexpectedly high
    masses of merging black holes detected last year. The study is an
    effort to bring together a broad set of ideas and observations to test
    how well they fit, and the fit is surprisingly good. If it is correct, then all
    galaxies, including our own, are embedded within a vast sphere of black
    holes each about 30 times the Sun's mass. In 2005, astronomers used
    the Spitzer space telescope to explore the background glow of infrared
    light in one part of the sky. They reported excessive patchiness in the
    glow and concluded that it was probably caused by the aggregate light of
    the first sources to illuminate the Universe, more than 13 billion years
    ago. Follow-up studies confirmed that that cosmic infrared background
    (CIB) showed similar unexpected structure in other parts of the sky. In
    2013, another study compared how the cosmic X-ray background (CXB)
    detected by the Chandra X-ray observatory compared to the CIB in the
    same area of the sky. The first stars emitted mainly optical and ultraviolet
    light, which today is stretched into the infrared by the expansion of
    space, so they should not contribute significantly to the CXB.
    Yet the irregular glow of low-energy X-rays in the CXB matched the
    patchiness of the CIB quite well. The only object we know of that can
    be sufficiently luminous across such a wide an energy range is a black
    hole. The research team concluded that primordial black holes must
    have been abundant among the earliest stars, making up at least about
    one out of every five of the sources contributing to the CIB. The
    nature of dark matter remains one of the most important unresolved
    issues in astrophysics. Scientists currently favour theoretical
    models that explain dark matter as an exotic massive particle, but so
    far searches have failed to turn up evidence that those hypothetical
    particles actually exist. NASA is currently investigating that issue
    as part of its Alpha magnetic spectrometer and Fermi gamma-ray space
    telescope missions. Those studies are providing increasingly
    sensitive results, slowly shrinking the box of parameters where dark
    matter particles can hide. The failure to find them has led to
    renewed interest in studying how well primordial black holes could
    work as dark matter. Physicists have outlined several ways in which
    the hot, rapidly expanding Universe could produce primordial black
    holes in the first thousandths of a second after the Big Bang. The
    older the Universe is when those mechanisms take hold, the larger the
    black holes can be. And because the window for creating them lasts
    only a tiny fraction of the first second, scientists expect that
    primordial black holes would exhibit a narrow range of masses. On
    Sept. 14, gravitational waves produced by a pair of merging black
    holes 1.3 billion light-years away were captured by the Laser
    Interferometer Gravitational-Wave Observatory (LIGO) facilities in
    Washington and Louisiana. That event marked the first-ever detection
    of gravitational waves. The signal provided LIGO scientists with
    information about the masses of the individual black holes, which were
    29 and 36 times the Sun's mass, plus or minus about four solar masses.
    Those values were both unexpectedly large and surprisingly similar.
    Depending on the mechanism at work, primordial black holes could have
    properties very similar to those that LIGO detected. If we assume
    that that is the case — that LIGO caught a merger of black holes
    formed in the early Universe — we can look at the consequences that
    that has on our understanding of how the cosmos ultimately evolved.
    New research analyzes what might have happened if dark matter
    consisted of a population of black holes similar to those detected by
    LIGO. The black holes distort the distribution of mass in the early
    Universe, adding a small fluctuation that has consequences hundreds of
    millions of years later, when the first stars begin to form. For much
    of the Universe's first 500 million years, normal matter remained too
    hot to coalesce into the first stars. Dark matter was unaffected by
    the high temperature because, whatever its nature, it primarily
    interacts through gravity. Aggregating by mutual attraction, dark
    matter first collapsed into clumps called mini-haloes, which provided
    a gravitational seed enabling normal matter to accumulate. Hot gas
    collapsed towards the mini-haloes, resulting in pockets of gas dense
    enough to collapse further on their own into the first stars. It can
    be shown that if black holes play the part of dark matter, that
    process occurs more rapidly and easily produces the lumpiness of the
    CIB detected in Spitzer data even if only a small fraction of
    mini-haloes manages to produce stars. As cosmic gas fell into the
    mini-haloes, their constituent black holes would naturally capture
    some of it too. Matter falling towards a black hole heats up and
    ultimately produces X-rays. Together, infrared light from the first
    stars and X-rays from gas falling into dark-matter black holes can
    account for the observed agreement between the patchiness of the CIB
    and the CXB. Occasionally, some primordial black holes will pass
    close enough to be gravitationally captured into binary systems.
    The black holes in each of those binaries will, over aeons, emit
    gravitational radiation, lose orbital energy and spiral inwards,
    ultimately merging into a larger black hole like the event LIGO
    observed. Future LIGO observing runs may tell us more about the
    Universe's population of black holes, so it may not be long before
    we know whether the scenario outlined here is supported or rejected.

    Space Telescope Science Institute (STScI)

    Astronomers using the Hubble space telescope have discovered that the
    Universe is expanding 5% to 9% faster than expected. That surprising
    finding may be an important clue to understanding those mysterious
    parts of the Universe that are said to make up 95% of everything and
    do not emit light, such as 'dark energy', dark matter, and 'dark
    radiation'. The team made the discovery by refining the Universe's
    current expansion rate to unprecedented accuracy, reducing the formal
    uncertainty to only 2.4%. It made the refinements by developing
    innovative techniques that improved the precision of distance
    measurements to far-away galaxies. Researchers looked for galaxies
    containing both Cepheid variable stars and Type Ia supernovae.
    Cepheid stars pulsate at rates that correspond to their true
    brightnesses, which can be compared with their apparent brightnesses
    as seen from here to determine their distances. Type Ia supernovae,
    another commonly used cosmic yardstick, are exploding stars that flare
    with the same brightness and are brilliant enough to be seen from very
    long distances. By measuring about 2,400 Cepheid stars in 19 galaxies
    and comparing the observed brightness of both types of stars, the
    Hubble users determined their true brightness and calculated distances
    to roughly 300 Type Ia supernovae in far-flung galaxies. The team
    compared those distances with the expansion of space as measured by
    the stretching of light from receding galaxies. Then the team used
    the two values to calculate how fast the Universe expands with time,
    or the Hubble constant.

    Bulletin compiled by Clive Down
    (c) 2016 The Society for Popular Astronomy

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