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  • richardmitnick 5:44 pm on October 31, 2013 Permalink | Reply
    Tags: , , , , NASA Galex,   

    From NASA/JPL at Caltech: “Galaxy Growth Examined Like Rings of a Tree” 

    October 31, 2013
    Whitney Clavin 818-354-4673
    Jet Propulsion Laboratory, Pasadena, Calif.
    whitney.clavin@jpl.nasa.gov

    – Like tree rings, inner and outer portions of a galaxy’s disk are a historical record
    — Two NASA missions find evidence that star formation bursts started in galaxy centers and spread outward
    — Unexplained ultraviolet light might come from a late phase in the lives of older stars

    gg

    Watching a tree grow might be more frustrating than waiting for a pot to boil, but luckily for biologists, there are tree rings. Beginning at a tree trunk’s dense core and moving out to the soft bark, the passage of time is marked by concentric rings, revealing chapters of the tree’s history.

    Galaxies outlive trees by billions of years, making their growth impossible to see. But like biologists, astronomers can read the rings in a galaxy’s disk to unravel its past. Using data from NASA’s Wide-field Infrared Survey Explorer (WISE) and Galaxy Evolution Explorer (GALEX), scientists have acquired more evidence for the “inside-out” theory of galaxy growth, showing that bursts of star formation in central regions were followed one to two billion years later by star birth in the outer fringes.

    “Initially, a rapid star-forming period formed the mass at the center of these galaxies, followed later by a star-forming phase in the outer regions. Eventually, the galaxies stop making stars and become quiescent,” said Sara Petty of Virginia Tech, Blacksburg, Va., lead author of a paper appearing in the October 2013 issue of the Astronomical Journal. “This later star-forming phase could have been caused by minor mergers with gas-rich neighbors, which provide the fuel for new stars.”

    The discovery may also solve a mystery of elderly galaxies. The galaxies in the study, known as “red and dead” for their red color and lack of new star births, have a surprising amount of ultraviolet light emanating from the outer regions. Often, ultraviolet light is generated by hot, young stars, but these galaxies were considered too old to host such a young population.

    The solution to the puzzle is likely hot, old stars. Petty and colleagues used a new multi-wavelength approach to show that the unexplained ultraviolet light appears to be coming from a late phase in the lives of older stars, when they blow off their outer layers and heat up.

    GALEX and WISE turned out to be the ideal duo for the study. GALEX was sensitive to the ultraviolet light, whereas WISE sees the infrared light coming from older stars. GALEX is no longer operating, but WISE was recently reactivated to hunt asteroids, a project called NEOWISE (see http://www.jpl.nasa.gov/news/news.php?release=2013-257 ). Both telescopes have large fields of view, allowing them to easily capture images of entire galaxies.

    “The synergy between GALEX and WISE produces a very sensitive measurement of where the hot, older stars reside in these red-and-dead galaxies,” said Don Neill, co-author of the paper from the California Institute of Technology, Pasadena. “This allows us to map the progress of star formation within each galaxy.”

    Ned Wright of UCLA, a co-author of the study and the principal investigator of WISE before it was reactivated, compares the multi-wavelength range of the two telescopes to musical notes, “WISE itself covers the equivalent of a three-octave range, while WISE and GALEX together cover a seven-octave range.”

    See the full article here.

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

    Caltech Logo
    jpl


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  • richardmitnick 9:21 pm on January 10, 2013 Permalink | Reply
    Tags: , , , , , NASA Galex   

    From NASA Galex: “NASA’s GALEX Reveals the Largest-Known Spiral Galaxy 

    NASA Galex Banner

    NASA Galex telescope

    Galaxy Evolution Explorer (Galex)

    This composite of the giant barred spiral galaxy NGC 6872 combines visible light images from the European Southern Observatory’s Very Large Telescope with far-ultraviolet (1,528 angstroms) data from NASA’s GALEX and 3.6-micron infrared data acquired by NASA’s Spitzer Space Telescope. A previously unsuspected tidal dwarf galaxy candidate (circled) appears only in the ultraviolet, indicating the presence of many hot young stars. IC 4970, the small disk galaxy interacting with NGC 6872, is located above the spiral’s central region. The spiral is 522,000 light-years across from the tip of one outstretched arm to the tip of the other, which makes it about 5 times the size of our home galaxy, the Milky Way. Images of lower resolution from the Digital Sky Survey were used to fill in marginal areas not covered by the other data.

    galaxy
    Credit: NASA’s Goddard Space Flight Center/ESO/JPL-Caltech/DSS

    The spectacular barred spiral galaxy NGC 6872 has ranked among the biggest stellar systems for decades. Now a team of astronomers from the United States, Chile and Brazil has crowned it the largest-known spiral, based on archival data from NASA’s Galaxy Evolution Explorer (GALEX) mission, which has since been loaned to the California Institute of Technology, Pasadena, Calif.

    Measuring tip-to-tip across its two outsized spiral arms, NGC 6872 spans more than 522,000 light-years, making it more than five times the size of our Milky Way galaxy.

    ‘Without GALEX’s ability to detect the ultraviolet light of the youngest, hottest stars, we would never have recognized the full extent of this intriguing system,’ said lead scientist Rafael Eufrasio, a research assistant at NASA’s Goddard Space Flight Center in Greenbelt, Md., and a doctoral student at Catholic University of America in Washington. He presented the findings Thursday at the American Astronomical Society meeting in Long Beach, Calif.”

    See the full article here.

    NASA Goddard

    The Galaxy Evolution Explorer (GALEX) is an orbiting ultraviolet space telescope launched on April 28, 2003. NASA cut off financial support for operations of GALEX in early February 2011 as it was ranked lower than other projects which were seeking a limited supply of funding. The California Institute of Technology negotiated to transfer control of GALEX and its associated ground control equipment to the California Institute of Technology in keeping with the Stevenson-Wydler Technology Innovation Act. Under this Act, excess research equipment owned by the US government can be transferred to educational institutions and non-profit organizations.[3] In May 2012, GALEX operations were transferred to Caltech.

    Caltech Logo

     
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