The SOCIETY for POPULAR ASTRONOMY Electronic News Bulletin No. 425 2016 July 3

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    The SOCIETY for POPULAR ASTRONOMY
    Electronic News Bulletin No. 425 2016 July 3

    SMALL ASTEROID IS THE EARTH'S CONSTANT COMPANION
    NAS
    A
    A small asteroid has been discovered in an orbit around the Sun that
    keeps it as a constant companion of the Earth, and it will remain so for
    centuries to come. As it orbits the Sun, the new-found asteroid,
    designated 2016 HO3, appears to circle around the Earth as well. It is
    too distant to be considered a true satellite of our planet, but it is
    the best and most stable example to date of a near-Earth companion.
    Since 2016 HO3 loops around our planet, but never ventures very far away
    as we both go round the Sun, we refer to it as a quasi-satellite of
    Earth. One other asteroid — 2003 YN107 — followed a similar orbital
    pattern for a while over 10 years ago, but it has since departed from
    our vicinity. The new asteroid is much more locked onto us. Calcula-
    tions indicate 2016 HO3 has been a stable quasi-satellite of the Earth
    for almost a century. In its yearly orbit round the Sun, the asteroid
    spends about half the time closer to the Sun than the Earth is, and
    passes ahead of our planet, and the other half of the time farther away,
    causing it to fall behind. Its orbit is also tilted a little, causing
    it to pass up and then down once each year through the Earth's orbital
    plane.
    The asteroid's orbit also undergoes a slow, back-and-forth twist over
    multiple decades. The asteroid's loops around the Earth drift a little
    ahead or behind from year to year, but when they drift too far forward
    or backward, the Earth's gravity is just strong enough to reverse the
    drift and hold onto the asteroid so that it never wanders farther away
    than about 100 times the distance of the Moon. The same effect also
    prevents it from ever approaching much closer than about 38 times the
    distance of the Moon. In effect, the small asteroid is caught in a
    little dance with the Earth. Asteroid 2016 HO3 was first observed on
    2016 April 27, by the Pan-STARRS 1 asteroid survey telescope in Hawaii.
    The size of the object has not yet been firmly established, but it is
    probably between 40 and 100 metres.

    EXTREME TRANS-NEPTUNIAN OBJECTS AND PLANET 9
    Plataforma SINC

    In an effort to discover a ninth planet in the Solar System (Pluto no
    longer having that distinction, being demoted), scientists in various
    countries have been trying to calculate its orbit from the paths
    followed by small bodies that move well beyond Neptune. Now,
    astronomers from Spain and Cambridge University have confirmed, with
    new calculations, that the orbits of the six extreme trans-Neptunian objects
    that served as a reference to announce the existence of Planet Nine are
    not as stable as it was thought. At the beginning of this year, astronomers
    announced that they had found evidence of the existence of a giant planet
    with a mass ten times larger than the Earth's in the confines of the Solar
    System. Moving in an unusually elongated orbit, the planet would take
    between 10,000 and 20,000 years to complete one revolution around the
    Sun. To arrive at that conclusion, the team ran computer simulations with
    input data based on the orbits of six extreme trans-Neptunian objects
    (ETNOs): Sedna, 2012 VP113, 2004 VN112, 2007TG422, 2013 RF98
    and 2010 GB174. Now, however, the team has considered the question
    the other way round: how would the orbits of those six ETNOs evolve if a
    Planet Nine, such as the one proposed, really did exist? With the orbit
    indicated by the Caltech astronomers for Planet Nine, calculations show
    that the six ETNOs would move in lengthy, unstable orbits. Those objects
    would escape from the Solar System in less than 1.5 billion years, and in
    the case of 2004 VN112, 2007 TG422 and 2013 RF98 they could
    abandon it in less than 300 million years; what is more important, their
    orbits would become unstable in just 10 million years, a really short time in
    astronomical terms.
    According to the new study, based on numerical (N-body) simulations, the
    orbit of the new planet would have to be modified slightly so that the
    orbits of the six ETNOs analysed would be really stable for a long time.
    Those results also lead to a new question: are the ETNOs a transient and
    unstable population or, on the contrary, are they permanent and stable?
    The behaviour of those objects in one way or the other affects the
    evolution of their orbits and also the numerical modelling. If the ETNOs
    are transient, they are being continuously ejected and must have a
    stable source located beyond 1,000 astronomical units (in the Oort
    cloud) where they come from. But if they are stable in the long term,
    then there could be many in similar orbits although we have not observed
    them yet. In any case, the statistical and numerical evidence obtained
    by the authors, both through this investigation and previous work, leads
    them to suggest that the most stable picture is one in which there is
    not just one planet, but rather several more beyond Pluto, in mutual
    resonance. The situation is reminiscent of the one leading to the
    discovery of Neptune, in which the French mathematician Urbain Le
    Verrier was the first to “discover” a new planet by means of laborious
    hand calculations based on the positions of Uranus, whereupon the German
    astronomer J. G Galle directly observed it. If Neptune was the first
    planet discovered by pen and paper, Planet Nine could be the first to
    be discovered entirely from computerized numerical calculations.

    STAR MAY HOLD CLUES TO PLANET FORMATION
    NASA

    In 1936, the young star FU Orionis began devouring material from its
    surrounding disc of gas and dust with a sudden voracity. During a
    three-month binge, the star became 100 times brighter, heating the disc
    around it to temperatures of up to 7,000°K. FU Orionis is still
    devouring gas to this day, although not as quickly. Its brightening is
    the most extreme event of its kind that has been confirmed around a star
    the size of the Sun, and may have implications for how stars and planets
    form. The intense baking of the star's surrounding disc probably
    changed its chemistry, permanently altering material that could one day
    turn into planets. Our own Sun may have gone through a similar
    brightening, which would have been a crucial step in the formation of
    the Earth and other planets in the Solar System. Visible-light
    observations of FU Orionis, which is about 1,500 light-years distant,
    have shown astronomers that the star's extreme brightness began slowly
    fading after its initial 1936 outburst. But astronomers wanted to know
    more about the relationship between the star and surrounding disc. Is
    the star still gorging on it? Is its composition changing? When will
    its brightness return to pre-outburst levels? To answer those
    questions, scientists needed to observe the star's brightness at
    infrared wavelengths to provide temperature measurements. The team
    compared infrared data obtained with the Stratospheric Observatory for
    Infrared Astronomy (SOFIA) to observations made with the Spitzer space
    telescope. By combining data collected from the two telescopes over a
    12-year interval, scientists were able to gain a perspective on the
    star's behaviour over time. Using those observations and other
    historical data, researchers found that FU Orionis had continued its
    rapid accretion after the initial brightening event — it has accreted
    the equivalent of 18 Jupiters in the last 80 years.
    The recent measurements provided by SOFIA inform researchers that the
    total amount of visible and infrared light energy coming out of the
    FU Orionis system decreased by about 13% over the 12 years since the
    Spitzer observations. Researchers found that the decrease has been
    caused by dimming of the star at short infrared wavelengths, but not at
    longer wavelengths. That means up to 13% of the hottest material of the
    disc has disappeared, while the cooler material has remained intact. A
    decrease in the hottest gas means that the star is eating the innermost
    part of the disc, but the rest of the disc has essentially not changed
    in the last 12 years. That result is consistent with computer models,
    but for the first time we are able to confirm the theory with
    observations. Astronomers predict, partly on the basis of the new
    results, that FU Orionis will run out of hot material to consume within
    the next few hundred years. At that point, it will return to the state
    it was in before the dramatic 1936 brightening event. Scientists are
    unsure what the star was like before or what set off the feeding frenzy.
    The material falling into the star is like water from a hose that is
    slowly being pinched off, and eventually the water will stop. If the
    Sun ever had a brightening event like FU Orionis did in 1936, it could
    explain why certain elements are more abundant on Mars than on Earth. A
    sudden 100-fold brightening would have altered the chemical composition
    of material close to the star, but not as much farther from it. Because
    Mars formed farther from the Sun, its component material would not have
    been heated up as much as the Earth's was. At a few hundred thousand
    years old, FU Orionis is a newborn in relation to the typical lifespan
    of a star. The 80 years of brightening and fading since 1936 represent
    only a tiny fraction of the star's existence so far, but those changes
    have happened to occur at a time when astronomers exist and could
    observe. It is surprising that an entire protoplanetary disc can change
    on such a short time-scale, within a human lifetime.

    MILKY WAY'S MISSING RED GIANTS
    Georgia Institute of Technology

    New computer simulations provide a conclusive test for a hypothesis of
    why the centre of the Milky Way appears to be filled with young stars
    but has very few old ones. According to the theory, the remnants of
    older, red-giant stars are still there, but they are not bright enough
    to be detected with telescopes. The simulations investigate the
    possibility that the red giants were dimmed after they were stripped of
    a large percentage of their mass millions of years ago during repeated
    collisions with an accretion disc at the Galactic Centre. The very
    existence of the young stars, seen in astronomical observations today,
    is an indication that such a gaseous accretion disc was present at the
    Galactic Centre, because the young stars are thought to have formed from
    it as recently as a few million years ago. The study is the first to
    run computer simulations on the theory, which was introduced in 2014.
    The team created models of red giants similar to those that are
    supposedly missing from the Galactic Centre — stars that are more than
    a billion years old and dozens of times larger in size than the Sun.
    They put them through a computerized version of a wind tunnel to
    simulate collisions with the gaseous disc that once occupied much of the
    space within half a parsec of the Galactic Centre. They varied orbital
    velocities and the disc's density to find the conditions required to
    cause significant damage to the red-giant stars.
    Red giants could have lost a significant portion of their mass only if
    the disc were very massive and dense. So dense that gravity would have
    already fragmented the disc on its own, helping to form massive clumps
    that became the building blocks of a new generation of stars. The
    simulations suggest that each of the red-giant stars orbited its way
    into and through the disc as many as dozens of times, sometimes taking
    as long as days to weeks to complete a single pass-through. Mass was
    stripped away with each collision as the star blistered the fragmenting
    disc's surface. It is a process that would have taken place 4 to 8
    million years ago, which is the same age as the young stars seen in the
    centre of the Milky Way today. The only way for that scenario to take
    place within that relatively short time frame would be if, to begin
    with, the disc that fragmented had a much larger mass than all the young
    stars that eventually formed from it — at least 100 to 1,000 times more
    mass. The impacts also probably lowered the kinetic energy of the red
    giant stars by at least 20–30%, shrinking their orbits and pulling them
    closer to the Milky Way's black hole. At the same time, the collisions
    may have torqued the surface and spun up the red giants, which are
    otherwise known to rotate relatively slowly in isolation.

    SMALL PLANETS HIDING IN GIANT CLOAKS
    RAS

    Hazes and clouds high up in the atmospheres of exo-planets may make
    them appear bigger than they really are, according to new research by
    astronomers at the Space Research Institute (IWF) of the Austrian
    Academy of Sciences. Since the first confirmed discovery in 1993,
    astronomers have found more than 3,000 planets in orbit around stars
    other than our Sun. A key goal now is to characterize known planets by
    mass, size and composition, in the effort to understand the evolution of
    planetary systems, and the prospects for 'Earthlike' planets that might
    support life. In 2014 the team used ESA's CoRoT space telescope to
    study the upper atmospheres of two low-mass planets that are regularly
    seen to transit in front of the star they orbit. The two planets orbit
    their star in 5 and 12 days, appear to be around 4 and 5 times the
    diameter of the Earth, and have respective masses of less than 6, and
    28, times that of the Earth. The outer, more massive planet, CoRoT-24c,
    is similar in mass to Neptune; the inner planet, CoRoT-24b, is less than
    a quarter as massive, but is similar in size, so seems to have a very
    low density. With orbits of such short periods, both planets must be
    close to the star and experience dramatic heating. The team modelled
    that, and found that the lower-mass planet would see its atmosphere
    evaporate within 100 million years, if it really is as big as is
    suggested. But the star is billions of years old, so the planet should
    have lost its atmosphere long ago. The solution seems to be that the
    planet is only about half as big as has been thought. It is suggested
    that an extended, very thin, atmosphere surrounds a relatively compact
    planet, but has high-altitude features that confuse observations. The
    radius is based on what we see when the planet makes its transit. The
    result is probably falsified by clouds and haze high in the atmosphere,
    in a region where the atmospheric pressure is very low. Such an effect
    needs to be considered by future exo-planet missions, like the ESA
    CHaracterising ExOPlanets Satellite (CHEOPS) mission that is due to be
    launched in late 2017. Results for some planets found by the Kepler
    observatory may also need to be re-evaluated. Since Kepler has also
    discovered several similar low-density and low-mass planets, it is very
    likely that the sizes measured for many of them also differ from the
    true values, so there could be a bias in the results. If the Austrian
    team is right, its conclusion has considerable implications, for example
    in the studies of planet populations and how the masses of planets
    relate to their sizes.

    DETECTION OF METHYL ALCOHOL IN PROTOPLANETARY DISC
    ESO

    The organic molecule methyl alcohol (methanol) has been found by the
    Atacama Large Millimetre/Submillimetre Array (ALMA) in the TW Hydrae
    protoplanetary disc. This is the first such detection of the compound
    in a young planet-forming disc. Methanol is the only complex organic
    molecule that unambiguously derives from an icy form and that has been
    detected in discs. Its detection helps astronomers to understand the
    chemical processes that occur during the formation of planetary systems
    and that ultimately lead to the creation of the ingredients for life.
    The protoplanetary disc around the young star TW Hydrae is the closest
    known example to Earth, at a distance of about 170 light-years. The
    system resembles what astronomers think the Solar System must have
    looked like during its formation more than four thousand million years
    ago. Furthermore, methanol is itself a building block for more complex
    compounds of pre-biotic importance, like amino-acid compounds. As a
    result, methanol plays a vital role in the creation of the rich organic
    chemistry needed for life. Gaseous methanol in a protoplanetary disc
    has a unique importance in astrochemistry. While other species detected
    in space are formed by gas-phase chemistry alone, or by a combination of
    both gas- and solid-phase generation, methanol is a complex organic
    compound which is formed solely in the ice phase via surface reactions
    on dust grains. The observation of methanol in the gas phase, combined
    with information about its distribution, implies that methanol formed on
    the disc's icy grains, and was subsequently released in gaseous form.
    This first observation helps to clarify the puzzle of the methanol
    ice–gas transition, and more generally the chemical processes in
    astrophysical environments.

    UNIVERSE'S FIRST LIFE BORN ON CARBON PLANETS?
    Harvard-Smithsonian Center for Astrophysics

    Our Earth consists of silicate rocks and an iron core with a thin veneer
    of water and life. But the first potentially habitable planets to form
    might have been very different. New research suggests that planet
    formation in the early Universe might have created carbon planets
    consisting of graphite, carbides, and diamond. Astronomers might find
    such diamond planets by searching a rare class of stars. The primordial
    Universe consisted mostly of hydrogen and helium, and lacked chemical
    elements like carbon and oxygen necessary for life as we know it. Only
    after the first stars exploded as supernovae and seeded the second
    generation did planet formation and life become possible. Astronomers
    examined a particular class of old stars known as carbon-enhanced
    metal-poor stars, or CEMP stars. Those anaemic stars contain only one
    hundred-thousandth as much iron as the Sun; evidently they formed before
    interstellar space had been widely seeded with heavy elements. Such
    stars are fossils from the young Universe. By studying them, we can
    look at how planets, and possibly life, got started. Although lacking
    in iron and other heavy elements compared to the Sun, CEMP stars have
    more carbon than would be expected given their age. That relative
    abundance would influence planet formation, as fluffy carbon dust grains
    clump together to form tar-black planets. From a distance, carbon
    planets would be difficult to tell apart from more Earth-like ones.
    Their masses and physical sizes would be similar. Astronomers would
    have to examine their atmospheres for signs of their true nature. Gases
    like carbon monoxide and methane would envelop those unusual planets.
    A dedicated search for planets around CEMP stars can be done by the
    transit technique.

    NAMES PROPOSED FOR NEW ELEMENTS
    BBC News

    Names have now been proposed for the four new chemical elements
    added to the periodic table in January. They are nihonium (with the
    symbol Nh), moscovium (Mc), tennessine (Ts), and oganesson (Og). Until
    now, the quartet has been referred to simply by the number of protons in
    each atom – 113, 115, 117 and 118, respectively. The elements are the
    first to be added to the famous table since 2011, and complete its seventh
    row. The names must go out to consultation for five months, but if
    there are no objections their confirmation should be a formality. That
    will come from the International Union of Pure and Applied Physics and
    the International Union of Pure and Applied Chemistry. All four
    elements are extreme — the synthetic creations of scientists. None of
    them exists outside the lab; they were made by bombarding two smaller
    (albeit still very large) atomic nuclei together. Theory predicts that
    there are 'islands of stability' in the high reaches of the periodic
    table where certain combinations should stick and hold together — but
    even then that state is usually only fleeting.
    Uranium (92 protons) is the heaviest naturally occurring element on
    Earth in any significant abundance. Nonetheless, the exercise does
    provide scientists with valuable insights into the structure of atomic
    nuclei and the properties that stem from it. As is customary, the
    discoverers of the new elements had the right to suggest a name. The
    rules state that that can reflect a mythological concept, a mineral, a
    place or country, a property or a scientist. The name also has to be
    unique and maintain 'historical and chemical consistency'. That
    explains why there is a lot of '-iums' in the table. Nihonium refers
    to the Japanese name for Japan. The atom was discovered at the RIKEN
    Nishina Centre for Accelerator Science. Moscovium was named after
    the Moscow region, the location of the Joint Institute for Nuclear
    Research in Dubna. Tennessine recognises the US state of Tennessee
    and the local contributions made to the discovery by the Oak Ridge
    National Laboratory and Vanderbilt University. Oganesson honours the
    nuclear physicist Yuri Oganessian, who has played a leading role in the
    search for new elements including the one that will now bear his name.

    OBSERVATION OF MOST DISTANT OXYGEN
    ESO

    A team of astronomers has used the Atacama Large Millimetre/submilli-
    metre Array (ALMA) to detect glowing oxygen in a distant galaxy seen
    just 700 million years after the Big Bang. That is the most distant
    galaxy in which oxygen has ever been unambiguously detected, and it is
    most likely being ionized by powerful radiation from young giant stars.
    That galaxy could be an example of one type of source responsible for
    cosmic reionization in the early history of the Universe. The galaxy,
    SXDF-NB1006-2, lies at a redshift of 7.2. The team was hoping to find
    out about the heavy chemical elements present in that galaxy, as they
    can tell us about the level of star formation, and hence provide clues
    about the period in the history of the Universe known as cosmic
    reionization. In the time before objects formed in it, the Universe was
    filled with electrically neutral gas. But when the first objects began
    to shine, a few hundred million years after the Big Bang, they emitted
    powerful radiation that started to break up those neutral atoms and
    ionize the gas. During that phase, known as cosmic reionization, the
    whole Universe changed dramatically. But there is much debate about
    what kinds of objects caused the reionization. Studying the conditions
    in very distant galaxies may help to answer that question.
    Before observing the distant galaxy, the researchers performed computer
    simulations to predict how easily they could expect to see evidence of
    ionized oxygen with ALMA. They also considered observations of similar
    galaxies that are much closer to the Earth, and concluded that the
    oxygen emission should be detectable, even at vast distances. They then
    carried out high-sensitivity observations with ALMA and found light from
    ionized oxygen in SXDF-NB1006-2, making that the most distant
    unambiguous detection of oxygen ever obtained. It is firm evidence for
    the presence of oxygen in the early Universe, only 700 million years
    after the Big Bang. Oxygen in SXDF-NB1006-2 was found to be ten times
    less abundant than it is in the Sun. The small abundance is expected
    because the Universe was still young and had a short history of star
    formation at that time. The team was unable to detect any emission from
    carbon in the galaxy, suggesting that that young galaxy contains very
    little un-ionized hydrogen gas, and also found that it contains only a
    small amount of dust, which is made up of heavy elements. The detection
    of ionized oxygen indicates that many very brilliant stars, several
    dozen times more massive than the Sun, have formed in the galaxy and
    are emitting the intense ultraviolet light needed to ionize the oxygen
    atoms. The lack of dust in the galaxy allows the intense ultraviolet
    light to escape and ionize vast amounts of gas outside the galaxy.
    SXDF-NB1006-2 must be an example of the type of light sources
    responsible for the cosmic reionization.

    CHIRAL MOLECULE DETECTED IN INTERSTELLAR SPACE
    National Radio Astronomy Observatory

    Like a pair of human hands, certain organic molecules have mirror-image
    versions of themselves, a chemical property known as chirality. Those
    so-called 'handed' molecules are essential for biology and have
    intriguingly been found in meteorites on Earth and comets in the Solar
    System. None, however, has been detected in interstellar space, until
    now. The molecule, propylene oxide (CH3CHOCH2), was found near the
    centre of the Galaxy in an enormous star-forming cloud of dust and gas
    known as Sagittarius B2 (Sgr B2). The research was undertaken primarily
    with the Green Bank Telescope (GBT) in West Virginia as part of the
    'Prebiotic Interstellar Molecular Survey'. Additional supporting
    observations were taken with the Parkes radio telescope in Australia.
    This is the first molecule detected in interstellar space that has the
    property of chirality, making it an advance in our understanding of how
    prebiotic molecules are made in the Universe and the effects they may
    have on the origins of life. Propylene oxide is among the most complex
    and structurally intricate molecules detected so far in space. Detect-
    ing that molecule opens the door for further experiments determining how
    and where molecular handedness emerges and why one form may be slightly
    more abundant than the other. Complex organic molecules form in inter-
    stellar clouds like Sgr B2 in several ways. The most basic pathway is
    through gas-phase chemistry, in which particles collide and merge to
    produce ever more complex molecules. Once organic compounds as
    large as methanol (CH3OH) are produced, however, the process
    becomes much less efficient.
    Astronomers believe that to form more complex molecules, like propylene
    oxide, thin mantles of ice on dust grains help link small molecules into
    longer and larger structures. Those molecules can then evaporate from
    the surface of the grains and further react in the gas of the surround-
    ing cloud. To date, more than 180 different molecules have been detected
    in space. Each molecule, as it naturally tumbles and vibrates in the
    near-vacuum interstellar medium, gives off a distinctive signature, a
    series of telltale spikes that appear in the radio spectrum. Larger and
    more complex molecules have correspondingly more complex signatures,
    making them harder to detect. To claim a definitive detection,
    scientists must observe multiple spectral lines associated with the same
    molecule. In the case of propylene oxide, the research team detected
    two such lines with the GBT. The third was at a frequency difficult to
    observe from the northern hemisphere owing to satellite radio
    interference. Scientists used the Parkes telescope to tease out the
    final spectral line needed to verify their results. The current data,
    however, do not distinguish between the left- and right-handed versions
    of the molecule. In addition to the same chemical composition, chiral
    molecules have the same melting, boiling, and freezing points, and the
    same spectra. Those spectra are like your hands' shadows. It is
    impossible to tell if a right hand or a left hand is casting the shadow.
    That presents a challenge to researchers trying to determine if one
    version of propylene oxide is more abundant than the other. Every
    living thing on Earth uses one, and only one, handedness of many types
    of chiral molecules. That trait, called homochirality, is critical for
    life and has important implications for many biological structures,
    including DNA's double helix. Scientists do not yet understand how
    biology came to rely on one handedness and not the other. The answer,
    the researchers speculate, may be found in the way these molecules
    naturally form in space before being incorporated into asteroids and
    comets and later deposited on young planets. The researchers believe
    that it may eventually be possible to determine if there is an excess of
    one handedness of propylene oxide over the other by examining how
    polarized light interacts with the molecules in space.

    Bulletin compiled by Clive Down

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