Published:  January 11th, 2007 07:20 EST
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Older galaxy pair has surprisingly youthful glow
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A pair of interacting galaxies might be experiencing the galactic equivalent of a mid-life crisis. For some reason, the pair, called Arp 82 (see photo), didn`t make their stars early on as is typical of most galaxies. Instead, they got a second wind later in life " about 2 billion years ago " and started pumping out waves of new stars as if they were young again. The new observations are from NASA`s Galaxy Evolution Explorer, NASA`s Spitzer Space Telescope and the Southeastern Association for Research in Astronomy Observatory at Kitt Peak, Ariz. Arp 82 is an interacting pair of galaxies with a strong bridge and a long tail. NGC 2535 is the big galaxy and NGC 2536 is its smaller companion. The disk of the main galaxy looks like an eye, with a bright pupil " in the center and oval-shaped eyelids. " Dramatic beads on a string " features are visible as chains of evenly spaced star-formation complexes along the eyelids. These are presumably the result of large-scale gaseous shocks from a grazing encounter. The colors of this galaxy indicate that the observed stars are young to intermediate in age, around 2 million to 2 billion years old, much less than the age of the universe (13.7 billion years). The pair first burst with new star formation about 2 billion years ago after swinging by each other. A second close passage more recently resulted in yet another batch of star formation. The puzzle is: why didn`t Arp 82 form many stars earlier, like most galaxies of that mass range? Scientifically, it is an oddball and provides a relatively nearby lab for studying the age of intermediate-mass galaxies. In more popular terms, think of this as an example of arrested development. For some reason, it took a kick-in-the-pants to get the stars forming recently, whereas most other galaxies of that mass range formed their stars much earlier (between 4 and 8 billion years ago). A journal article with a detailed analysis of these data has been accepted by the Astronomical Journal. This research has been sponsored by NASA. Contact: Mark Hancock, East Tennessee State University, Department of Physics, Astronomy, and Geology, (423) 439-5607, hancockm@etsu.edu. PHOTO CREDIT: NASA/JPL-Caltech/M. Hancock, B.J. Smith, C. Struck, M.L. Giroux, P.N. Appleton, V. Charmandaris and W.T. Reach. Graphics and additional information about the Galaxy Evolution Explorer is online at www.nasa.gov/galex/. More information about Spitzer is online at www.spitzer.caltech.edu/spitzer. The California Institute of Technology in Pasadena, Calif., leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA`s Jet Propulsion Laboratory, also in Pasadena, manages the mission and built the science instrument. The mission was developed under NASA`s Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. Researchers sponsored by Yonsei University in South Korea and the Centre National d`Etudes Spatiales (CNES) in France collaborated on this mission. JPL manages the Spitzer Space Telescope mission for NASA`s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Caltech manages JPL for NASA. East Tennessee State University
Box 70267
Johnson City, TN 37614-1700
(423) 439-1000 Source:JPL
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