Stellar Extremophiles   
       
   Nov. 7, 2011: Back in the 1970s, biologists were amazed to discover a form of   
   life they never expected.  Tiny microorganisms with ancient DNA were living in   
   the hot springs of Yellowstone National Park.  Instead of dissolving in the   
   boiling waters, the microbes were thriving, ringing the springs with vibrant   
   color.   
       
   Scientists coined the term extremophile, which means "extreme-loving", to   
   describe the creatures--and the hunt was on for more.  Soon, extremophiles   
   were found living in deep Antarctic ice, the cores of nuclear reactors, and   
   other unexpected places.  Biology hasn't been the same since.   
       
   Could astronomy be on the verge of a similar transformation?   
       
   Researchers using a NASA space telescope named GALEX have discovered a new   
   kind of extremophile: extreme-loving stars.   
       
   "We're finding stars in extreme galactic environments where star formation   
   isn't supposed to happen," explains GALEX project scientist Susan Neff of the   
   Goddard Space Flight Center. "This is a very surprising development."   
       
   This composite (radio+UV) image shows long octopus-like arms of star formation   
   stretching far away from the main disk of spiral galaxy M83. [more] [video]   
       
   http://www.youtube.com/watch?v=2k-XgLi1KgA   
       
   GALEX, which stands for "Galaxy Evolution Explorer," is an ultraviolet space   
   telescope with a special ability: It is super-sensitive to the kind of UV rays   
   emitted by the youngest stars.  This means the observatory can detect stars   
   being born at very great distances from Earth, more than halfway across the   
   Universe.  The observatory was launched in 2003 on a mission to study how   
   galaxies change and evolve as new stars coalesce inside them.   
       
   GALEX accomplished that mission-and more.   
       
   "In some GALEX images, we see stars forming outside of galaxiesin places where   
   we thought the gas density would be too low for star birth to occur," says   
   GALEX team member Don Neil of Caltech.   
       
   Stars are born when interstellar clouds of gas collapse and contract under the   
   pull of their own gravity.  If a cloud gets dense and hot enough as it   
   collapses, nuclear fusion will kick in and-voila!--a star is born.   
       
   The spiral arms of the Milky Way are a "goldilocks zone" for this process.   
   "Here in the Milky Way we have plenty of gas.  It's a cozy place for stars to   
   form," says Neil.   
       
   But when GALEX looks at other more distant spiral galaxies, it sees stars   
   forming far outside the gassy spiral disk.   
       
   "I was dumbfounded," he says. "These stars are truly 'living on the edge.'"   
       
   Spirals aren't the only galaxies with stellar extremophiles. The observatory   
   has also found stars being born   
       
   --in elliptical and irregular galaxies thought to be gas-poor (e.g., 1, 2)   
       
   --in the gaseous debris of colliding galaxies (1, 2)   
       
   --in vast "comet-like" tails that trail behind some fast-moving galaxies (1, 2)   
       
   --in cold primordial gas clouds, which are small and barely massive enough to   
   hang together   
       
   So much for the Goldilocks Zone.  According to GALEX, stellar extremophiles   
   populate just about every nook and cranny of the cosmos where a wisp of gas   
   can get together to make a new sun.   
       
   "This could be telling us something profound about the star-forming process,"   
   says Neff.  "There could be ways to make stars in extreme environments that we   
   haven't even thought of yet."   
       
   Will extremophiles transform astronomy as they did biology?  It's too soon to   
   say, insist the researchers. But GALEX has definitely given them something to   
   think about.   
       
       
   Author:Dr. Tony Phillips| Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
   More Information   
   GALEX -- home page   
   http://www.galex.caltech.edu/   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.64   
    * Origin: NCS BBS (1:3828/7)