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GALEX - Discovered Giant Rings of New Stars Around Ancient, Dead Galaxies"

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  • derhexerus
    Fascinating post from the Daily Galaxy. Stellar development goes on and on. Chris ____________________________________ From: vlandi@yahoo.com To:
    Message 1 of 1 , Jun 29, 2013
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      Fascinating post from the Daily Galaxy. Stellar development goes on and


      From: vlandi@...
      To: derhexer@...
      Sent: 6/29/2013 6:05:30 P.M. Eastern Daylight Time
      Subj: The Daily Galaxy: News from Planet Earth & Beyond

      _The Daily Galaxy: News from Planet Earth & Beyond_

      _NASA Turns Off Galaxy Evolution Explorer --"Discovered Giant Rings of New
      Stars Around Ancient, Dead Galaxies"_
      Posted: 29 Jun 2013 07:51 AM PDT


      NASA has turned off its _Galaxy Evolution Explorer_
      (http://www.galex.caltech.edu/) (GALEX) after a decaden of operations in which the venerable
      space telescope used its ultraviolet vision to study hundreds of millions of
      galaxies across 10 billion years of cosmic time. In the space telescope's
      last year, it scanned across large patches of sky, including the bustling,
      bright center of our Milky Way. The telescope spent time staring at certain
      areas of the sky, findingexploded stars, called supernovae, and monitoring
      how objects, such as the centers of active galaxies,change over time. GALEX
      also scanned the sky for massive, feeding black holes and shock waves from
      early supernova explosions."GALEX is a remarkable accomplishment," said
      Jeff Hayes, NASA's GALEX program executive inWashington. "This small Explorer
      mission has mapped and studied galaxies in the ultraviolet, lightwe cannot
      see with our own eyes, across most of the sky."
      In 2010, NASA astronomers have found mysterious, giant loops of
      ultraviolet light in aged, massive galaxies, which seem to have a second lease on
      life. Somehow these "over-the-hill galaxies" have been infused with fresh gas
      to form new stars that power these truly gargantuan rings, some of which
      could encircle several Milky Way galaxies.
      The discovery of these rings implies that bloated galaxies presumed
      "dead" and devoid of star-making can be reignited with star birth, and that
      galaxy evolution does not proceed straight from the cradle to the grave.
      "In a galaxy's lifetime, it must make the transition from an active,
      star-forming galaxy to a quiescent galaxy that does not form stars," said Samir
      Salim, lead author of a recent study and a research scientist in the
      department of astronomy at Indiana University, Bloomington. "But it is possible
      this process goes the other way, too, and that old galaxies can be
      The findings came courtesy of the Galaxy Evolution Explorer and _Hubble
      Space Telescope_ (http://hubble.nasa.gov/) . First, the Galaxy Evolution
      Explorer surveyed a vast region of the sky in ultraviolet light. The satellite
      picked out 30 elliptical and lens-shaped "early" galaxies with puzzlingly
      strong ultraviolet emissions but no signs of visible star formation.
      Early-type galaxies, so the scientists' thinking goes, have already made their
      stars and now lack the cold gas necessary to build new ones.
      The Galaxy Evolution Explorer could not discern the fine details of these
      large, rounded galaxies gleaming in the ultraviolet, so to get a closer
      look, researchers turned to the Hubble Space Telescope. What they saw shocked
      them: three-quarters of the galaxies were spanned by great, shining rings
      of ultraviolet light, with some ripples stretching 250,000 light-years. A
      few galaxies even had spiral-shaped ultraviolet features.
      "We haven't seen anything quite like these rings before," said Michael
      Rich, co-author of the paper and a research astronomer at UCLA. "These
      beautiful and very unusual objects might be telling us something very important
      about the evolution of galaxies."
      Astronomers can tell a galaxy's approximate age just by the color of its
      collective starlight. Lively, young galaxies look bluish to our eyes due to
      the energetic starlight of their new, massive stars. Elderly galaxies
      instead glow in the reddish hues of their ancient stars, appearing "old, red and
      dead," as astronomers bluntly say. Gauging by the redness of their
      constituent stars, the galaxies seen by the Galaxy Evolution Explorer and Hubble
      are geezers, with most stars around 10 billion years old.
      But relying on the spectrum of light visible to the human eye can be
      deceiving, as some of us have found out after spending a day under the sun's
      invisible ultraviolet rays and getting a sunburn. Sure enough, when viewed in
      the ultraviolet part of the spectrum, these galaxies clearly have more
      going on than meets the eye.
      Some ultraviolet starlight in a few of the observed galaxies might just be
      left over from an initial burst of star formation. But in most cases, new
      episodes of star birth must be behind the resplendent rings, meaning that
      fresh gas has somehow been introduced to these apparently ancient galaxies.
      Other telltale signs of ongoing star formation, such as blazing hydrogen
      gas clouds, might be on the scene as well, but have so far escaped detection.
      Just where the gas for this galactic resurrection came from and how it has
      created rings remains somewhat perplexing. A merging with a smaller galaxy
      would bring in fresh gas to spawn hordes of new stars, and could in rare
      instances give rise to the ring structures as well.
      But the researchers have their doubts about this origin scenario. "To
      create a density shock wave that forms rings like those we've seen, a small
      galaxy has to hit a larger galaxy pretty much straight in the center," said
      Salim. "You have to have a dead-on collision, and that's very uncommon."
      Rather, the rejuvenating spark more likely came from a gradual sopping-up
      of the gas in the so-called intergalactic medium, the thin soup of material
      between galaxies. This external gas could generate these rings, especially
      in the presence of bar-like structures that span some galaxies' centers.
      Ultimately, more observations will be needed to show how these galaxies
      began growing younger and lit up with humongous halos. Salim and Rich plan to
      search for more evidence of bars, as well as faint structures that might
      be the remnants of stellar blooms that occurred in the galaxies' pasts.
      Rather like recurring seasons, it may be that galaxies stirred from winter can
      breed stars again and then bask in another vibrant, ultraviolet-soaked
      Operators at _Orbital Sciences Corporation_ (http://www.orbital.com/) in
      Dulles, Va., sent the signal to decommission GALEX at12:09 p.m. PDT (3:09
      p.m. EDT) Friday, June 28. The spacecraft will remain in orbit for at least
      65 years,then fall to Earth and burn up upon re-entering the atmosphere.
      GALEX met its prime objectives and themission was extended three times before
      being cancelled.
      In addition to finding giant rings of new stars around old, dead galaxies,
      hghlights from the mission's decade of sky scans include: discovering a
      gargantuan, comet-like tail behind a speeding star called Mira; catching a
      black hole "red-handed" as it munched on a star; independently confirming the
      nature of dark energy; and discovering a missing link in galaxy evolution
      -- the teenage galaxies transitioning from young to old.
      The mission also captured a dazzling collection of snapshots, showing
      everything from ghostly
      nebulas to a spiral galaxy with huge, spidery arms.
      In a first-of-a-kind move for NASA, the agency in May 2012 loaned GALEX to
      the California
      Institute of Technology in Pasadena, which used private funds to continue
      operating the satellite
      while NASA retained ownership. Since then, investigators from around the
      world have used GALEX
      to study everything from stars in our own Milky Way galaxy to hundreds of
      thousands of galaxies 5
      billion light-years away.
      "In the last few years, GALEX studied objects we never thought we'd be
      able to observe, from the
      _Magellanic Clouds_ (http://en.wikipedia.org/wiki/Magellanic_Clouds) to
      bright nebulae and supernova remnants in the galactic plane," said David
      Schiminovich of _Columbia University_
      (Columbia%20University)&t=h) , N.Y., N.Y, a longtime GALEX team member who led science
      operations over the past year. "Some of its most beautiful and
      scientifically compelling images are
      part of this last observation cycle."
      Data from the last year of the mission will be made public in the coming
      "GALEX, the mission, may be over, but its science discoveries will keep on
      going," said Kerry
      Erickson, the mission's project manager at NASA's _Jet Propulsion
      Laboratory_ (http://maps.google.com/maps?ll=34.20
      16944444,-118.171666667&spn=0.01,0.01&q=34.2016944444,-118.171666667 (Jet%20Propulsion%20Laboratory)&t=h) in
      Pasadena, Calif.
      A slideshow showing some of the popular GALEX images is online at:
      Graphics and additional information about the Galaxy Evolution Explorer
      are online at:
      http://www.nasa.gov/galex Related articles

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      (http://www.dailygalaxy.com/my_weblog/2013/05/galaxy-evolution-fueled-by-giant-cosmic-webs.html) _Galaxy Evolution Fueled By Giant Cosmic Webs_

      (http://www.dailygalaxy.com/my_weblog/2013/05/massive-missing-link-galaxy-discovered-10-times-size-of-milky-way.html) _Massive "Missing-Link" Galaxy
      Discovered --10 Times Size of Milky Way_


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