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  • richardmitnick 7:29 am on September 11, 2017 Permalink | Reply
    Tags: , , , , , , SAO, Super-Earths a juicy target for new space telescope   

    From SAO via Cosmos: “Super-Earths a juicy target for new space telescope” 

    Smithsonian Astrophysical Observatory
    Smithsonian Astrophysical Observatory

    COSMOS

    11 September 2017
    Andrew Masterson

    NASA/ESA/CSA Webb Telescope annotated

    The discovery of three “super-Earth” planets orbiting a dwarf star roughly 97 light years away provides a juicy target for the James Webb Space Telescope to be launched later this year, say US astronomers.

    In a paper posted on the pre-print science platform arXiv, a team of scientists led by Joseph Rodriguez from the Harvard-Smithsonian Centre for Astrophysics in Massachusetts, US, say the discovery affords a rare opportunity to investigate the dividing line between smaller rocky planets and larger gaseous ones.

    The planets, dubbed GJ 9827-b, -c, and –d, all orbit a K-type dwarf star, and do so rapidly, with orbits that range between 1.2 and 6.2 Earth-days. The frequency of their orbit means that the new space telescope – a joint venture between NASA and the European and Canadian space agencies – will be able to monitor them many times as they move in front of their host star, potentially revealing a wide array of valuable information.

    Rodriguez and colleagues are particularly excited about the discovery because two of them fall within a size range that so far seems rare – or at least elusive.

    To date, more than 3000 exoplanets have been identified, with the Kepler mission adding at least another 4500 candidates to the list.

    The California Kepler Survey, operated by NASA, has so far logged precise radii for 2000 identified planets and produced a surprising result. Almost all of them fall in a range that tops out at one-and-a-half times the radius of Earth, or starts at two.

    This has led to the observation that so far all exoplanets seem to be either super-Earths or mini-Neptunes.

    2
    PLANETARY COUSINS Planets may be lumped into two groups: smaller and rocky like Kepler-452b (left), or bigger and gassy like Kepler-22b (right). W. Stenzel/NASA Ames. Science News.

    The key difference, of course, is that those on the Earth-side of the divide are rocky, and those on the Neptune side are gaseous.

    One theory for the puzzling lack of intermediates is that the rocky “sub-Neptune” planets recorded so far orbit comparatively close to their host stars. This may mean that solar radiation burns off the thick gaseous envelopes that cloak their more distant neighbours, leaving only small rocky cores.

    GJ 9827-b, at 1.64 Earth radii, and GJ 9827-d, at 2.08, fall between the two divisions, potentially affording strong opportunities to study the transitional zone between rocky Earths and gassy Neptunes. GJ 9827-c has a radius of 1.29 Earth equivalents, and should therefore be simply rocky.

    The short orbit periods of the three planets, the researchers note, will enable repeated observations over a limited timespan.

    “The planets span the transition from rocky to gaseous planets, so the characteristics of their atmospheres and interior structures may illuminate how the structure and composition of small planets change with radius,” the scientists write.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    About CfA

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy. The long relationship between the two organizations, which began when the SAO moved its headquarters to Cambridge in 1955, was formalized by the establishment of a joint center in 1973. The CfA’s history of accomplishments in astronomy and astrophysics is reflected in a wide range of awards and prizes received by individual CfA scientists.

    Today, some 300 Smithsonian and Harvard scientists cooperate in broad programs of astrophysical research supported by Federal appropriations and University funds as well as contracts and grants from government agencies. These scientific investigations, touching on almost all major topics in astronomy, are organized into the following divisions, scientific departments and service groups.

     
  • richardmitnick 9:55 pm on October 12, 2016 Permalink | Reply
    Tags: , , , SAO   

    From SAO: “Millisecond Pulsars” 

    Smithsonian Astrophysical Observatory
    Smithsonian Astrophysical Observatory

    September 30, 2016 [This never came to social media.]

    1
    An artist’s impression of a millisecond pulsar and its companion. The pulsar (seen in blue with two radiation beams) is accreting material from its bloated red companion star and increasing its rotation rate. Astronomers have measured the orbital parameters of four millisecond pulsars in the globular cluster 47 Tuc and modeled their possible formation and evolution paths. European Space Agency & Francesco Ferraro (Bologna Astronomical Observatory)

    When a star with a mass of roughly ten solar masses finishes its life, it explodes as a supernova, leaving behind a neutron star as remnant “ash.” Neutron stars have masses of one-to-several suns but they are tiny in diameter, only tens of kilometers. They spin rapidly, and when they have associated magnetic fields, charged particles caught in them emit electromagnetic radiation in a lighthouse-like beam that can sweep past the Earth with great regularity every few seconds or less. These kinds of neutron stars are called pulsars, and they are dramatic, powerful probes of supernovae, their progenitor stars, and the properties of nuclear matter under the extreme conditions that exist in these stars.

    Millisecond pulsars are ones that spin particularly rapidly, hundreds of times per second. Astronomers have concluded that these objects must be increasing their rotation rates through the accretion of material from a nearby companion star. There are nearly 3000 known millisecond pulsars. About five percent of them are found in globular clusters — gravitationally bound, roughly spherical ensembles of stars containing as many as a million stars, with sizes as small as only tens of light-years in diameter. Their crowded environments provide ideal conditions for forming binary stars, and nearly eighty percent of the pulsars in globular clusters are millisecond pulsars. The globular cluster 47 Tucanae (47 Tuc) has twenty-five of them.

    CfA astronomer Maureen van den Berg was part of a team of astronomers that studied four unusual millisecond binary pulsars in 47 Tuc whose orbital parameters were unknown. Orbits are key to understanding the origin and evolution of pulsars, their mass transfer and speed-up rates, and even the precise masses of the stars. The scientists analyzed data from 519 radio observations of 47 Tuc assembled over sixteen years. The most shortest period pulsar in the set has a period of only 0.15 days. The longest one is 10.9 days (by the way, both are known to nine decimal places) and has an orbit that is even more circular than the Earth’s — in fact, it is the most circular system ever found in a globular cluster. The astronomers estimate that this binary pulsar probably formed when a neutron star encountered a binary star, captured its companion from the binary, and then began accreting material from it to become a pulsar. (A second, less likely scenario is also possible in which the binary pair formed and also evolved together.) The scientists completed similar analyses for the other three objects. The results, the first in a series of papers on the millisecond pulsars in 47 Tuc, characterize for the first time four of its pulsars including one of its most unusual ones, and provide new insights into how these objects formed and the environmental conditions within a globular cluster.

    Reference(s):

    Long-term Observations of the Pulsars in 47 Tucanae – I. A Study of Four Elusive Binary Systems, A. Ridolfi, P. C. C. Freire, P. Torne, C. O. Heinke, M. van den Berg, C. Jordan, M. Kramer, C. G. Bassa, J. Sarkissian, N. D’Amico, D. Lorimer, F. Camilo, R. N. Manchester and A. Lyne, MNRAS 462, 2918, 2016.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    About CfA

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy. The long relationship between the two organizations, which began when the SAO moved its headquarters to Cambridge in 1955, was formalized by the establishment of a joint center in 1973. The CfA’s history of accomplishments in astronomy and astrophysics is reflected in a wide range of awards and prizes received by individual CfA scientists.

    Today, some 300 Smithsonian and Harvard scientists cooperate in broad programs of astrophysical research supported by Federal appropriations and University funds as well as contracts and grants from government agencies. These scientific investigations, touching on almost all major topics in astronomy, are organized into the following divisions, scientific departments and service groups.

     
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