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  • richardmitnick 12:36 pm on July 9, 2014 Permalink | Reply
    Tags: , , , , Smithsonian Astrophysical Observatory   

    From CfA: “Gemini Reveals a Gravitational Wave Source in Hiding” 

    Smithsonian Astrophysical Observatory
    Smithsonian Astrophysical Observatory

    July 9, 2014
    No Writer credit

    [Albert] Einstein’s Theory of General Relativity predicts that accelerated masses emit gravitational waves, or ripples in space-time. Even though gravitational waves have yet to be detected directly, we expect that there are more than hundred million gravitational wave sources in our own galaxy. However, as of today, we know of only a few such sources.

    A team of researchers, led by Dr. Mukremin Kilic of the University of Oklahoma and Dr. Warren Brown of the Smithsonian Astrophysical Observatory, have recently identified one of the best (and perhaps the most powerful) gravitational wave sources currently known using the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North telescope and the Blue Channel spectrograph on the 6.5-meter MMT Telescope. Known as WD 0931+444, the object was first identified in 1982, and classified as a white dwarf with a low-mass M-dwarf [red dwarf] stellar companion.

    Gemini North telescope
    Gemini North Telescope

    MMT Telescope
    MMT telescope

    This new data from Gemini and MMT reveal that the white dwarf in this system is not in a binary with the M dwarf. Instead, it is orbiting another invisible white dwarf every 20 minutes. Thanks to the large collecting area of the Gemini and MMT telescopes, the team was able to obtain high quality optical spectroscopy of this system every 2 minutes and resolve the 20 minute orbital period.

    The orbital separation of the two stars is only 20 percent of the size of the Sun. These two stars will lose angular momentum through gravitational wave radiation and merge in less than nine Million years. Depending on the inclination angle (which is currently unknown) the pair may merge even faster, in only a few million years. This previously unknown source is believed to be stretching everything around us (due to gravity waves) by a factor of 10-22 (or more) every 10 minutes!

    The discovery of the true nature of WD 0931+444 indicates that there are likely many other strong gravitational wave sources hiding in plain sight. Some of these hidden sources can be identified through further optical follow-up observations as in this work. However, the direct detection of gravitational waves from these sources has to wait for a space-based gravitational wave mission like the evolved Laser Interferometer Space Antenna, which will likely not be operational until 2034 as currently envisioned.”

    ESA LISA Pathfinder
    ESA/LISA

    The paper can be accessed at: http://arxiv.org/abs/1406.3346

    See the full article here.
    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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  • richardmitnick 1:01 pm on May 9, 2014 Permalink | Reply
    Tags: , , , , Smithsonian Astrophysical Observatory   

    From CFA: “Clusters of Massive New Stars” 

    Smithsonian Astrophysical Observatory

    Smithsonian Astrophysical Observatory

    May 9, 2014
    No Writer Credit

    Over ninety percent of the stars in our galaxy were born in stellar nurseries, clusters of stars nestled deep within clouds of dust and molecular gas. These young natal environments are key targets for astronomers who study star formation because they retain imprints of the initial conditions that produced the stars and the dynamical environments under which they evolved. Clusters with massive stars (stars more than a few solar masses in size) are of particular interest since both the formation of massive stars and their impact on other cluster members are poorly understood, for several fundamental reasons. Massive stars begin hydrogen burning while they are still growing and hence quickly develop strong winds and ultraviolet radiation that inhibit their further growth while at the same time disrupting the nursery with shock waves and ionizing light. Moreover, because massive stars evolve quickly they do not linger in any particular stage of development long enough for easy study, and they remain obscured by the not-yet-disbursed natal dust. None of these issues applies to the formation of lower mass stars.

    clusters
    A Spitzer three-color infrared image of the massive star-forming cluster in the W5-East molecular cloud. CfA astronomers have used the infrared images to survey the populations of embedded young stars in this and four other regions. The contours show the extent of ionizing radiation from embedded stars; white arrows show radiation from external, hot stars. The scale marker indicates a length of 6.58 light-years.

    CfA astronomers Luis Chavarria, Joe Hora, Gus Muench, and Giovanni Fazio and two colleagues undertook a study of massive stellar clusters with the Spitzer Space Telescope, whose infrared camera can peer inside dusty regions. They chose five massive clusters relatively nearby (about six thousand light-years) and performed a detailed census of their populations using the infrared colors of the individual stars to characterize the clusters’ sizes and stages of development.

    NASA Spitzer Telescope
    NASA/Spitzer

    The astronomers report finding 3021 young stars in their set of five clusters, a large enough sample to draw significant conclusions. The youngest group of these stars, a subset of 539, are found in regions where the cloud material is densest, supporting the general picture of cluster formation. The scientists also find that massive young stars form preferentially in filamentary (rather than spherical) structures that subsequently fragment, probably due to turbulence effects.

    See the full article here.
    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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  • richardmitnick 11:32 am on February 28, 2014 Permalink | Reply
    Tags: , , , , Smithsonian Astrophysical Observatory, VERITAS Gamma Ray Telescope   

    From S.A.O. : “An Extended Gamma-Ray Source with No Known Counterpart” 

    Smithsonian Astrophysical Observatory

    February 28, 2014
    No Writer Credit

    A look at CfA discoveries from recent journals

    Gamma-rays are the most energetic known form of electromagnetic radiation, with each gamma ray being at least one hundred thousand times more energetic than an optical light photon. The most potent gamma rays, the so-called VHE (very high energy) gamma rays, pack energies a billion times this amount, or even more. Astronomers think that VHE gamma rays are produced in the environment of the winds or jets of the compact, ultra-dense remnant ashes of massive stars left behind from supernova explosions.

    There are two kinds of compact objects produced in supernovae: black holes and neutron stars (stars made up predominantly of neutrons, having densities equivalent to the mass of the Sun packed into a volume about 10 kilometers in radius). The winds or jets from the environments of such objects, including the kind called pulsars, can accelerate charged particles to very close to the speed of light. When light scatters off such energetic particles it becomes energized as well, sometimes turning into VHE gamma rays. At least this is the most popular current theory. One of the first known VHE sources was spotted about fifteen years ago in the direction of the constellation of Cygnus. It was unusual because, unlike most other known VHE sources which had counterparts seen at optical, radio, or other wavelengths, this new source had no known counterpart. With no other information available, its exact nature was mysterious.

    Recently a pulsar was discovered in the general vicinity, renewing interest in the source. CfA astronomers Wystan Benbow, Matteo Cerruti, Pascal Fortin, Nicola Galante, Emmet Thomas, and Trevor Weekes along with a large team of colleagues tackled the puzzle using the VERITAS gamma-ray telescope at the Fred L. Whipple Observatory in Arizona. They obtained very long, sensitive observations of the VHE source in Cygnus, and for the first time were able to refine the location and to determine that the emission was not point-like but slightly extended and asymmetric in shape. The astronomers conclude for several reasons that the newly found pulsar is probably not the origin of the VHE emission.

    Veritas Telescope
    VERITAS

    Remarkably, even with the refined location, images at other wavelengths reveal no point sources. In the infrared images, however, the region can be characterized by the fact that it lacks any dust emission and so appears dark while its surroundings glow with cool dust emission. The dark region is very nearly the same shape as the gamma-ray region, making the source even more mysterious than before. However, if the object were a faint pulsar whose wind produced VHE gamma-rays, it might, in some scenarios, also have blown away all the local dust to clear a void like the one seen in the infrared. More work is needed to understand this intriguing object but the current work, with its sensitivity and spatial resolution results, represents an important advance in the field of gamma-ray astronomy.

    See the full article here.
    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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