Discovered: Stars as Cool as the Human Body   
       
   August 24, 2011: Scientists using data from NASA's Wide-field Infrared Survey   
   Explorer (WISE) have discovered six "Y dwarfs"-- star-like bodies with   
   temperatures as cool as the human body.   
   [...]   
   This artist's conception illustrates what a "Y dwarf" might look like. Y   
   dwarfs are the coldest star-like bodies known, with temperatures that can be   
   even cooler than the human body. [more] Astronomers hunted these dark orbs for   
   more than a decade without success. When viewed with a visible-light   
   telescope, they are nearly impossible to see. WISE's infrared vision allowed   
   the telescope to finally spot the faint glow of a half dozen Y dwarfs   
   relatively close to our sun, within a distance of about 40 light-years.   
       
   "WISE scanned the entire sky for these and other objects, and was able to spot   
   their feeble light with its highly sensitive infrared vision," says Jon Morse,   
   Astrophysics Division director at NASA Headquarters in Washington.   
       
   The Y's are the coldest members of the brown dwarf family. Brown dwarfs are   
   sometimes referred to as "failed" stars. They are too low in mass to fuse   
   atoms at their cores and thus don't burn with the fires that keep stars like   
   our sun shining steadily for billions of years. Instead, these objects cool   
   and fade with time, until what little light they do emit is at infrared   
   wavelengths. The atmospheres of brown dwarfs are similar to those of gas giant   
   planets like Jupiter, but they are easier to observe because they are alone in   
   space, away from the blinding light of a parent star.   
       
   So far, WISE data have revealed 100 new brown dwarfs.  Of these, six are   
   classified as cool Y's. One of the Y dwarfs, called WISE 1828+2650, is the   
   record holder for the coldest brown dwarf with an estimated atmospheric   
   temperature cooler than room temperature, or less than 80 degrees Fahrenheit   
   (25 degrees Celsius).   
   [...]   
   WISE 1828+2650, the coldest brown dwarf known so far, is denoted by a green   
   dot in very center of this infrared image. The chilly star-like body isn't   
   even as warm as a human body, at less than about 80 degrees Fahrenheit. [more]   
       
   "The brown dwarfs we were turning up before this discovery were more like the   
   temperature of your oven," says Davy Kirkpatrick, a WISE science team member   
   at the Infrared Processing and Analysis Center at Caltech. "With the discovery   
   of Y dwarfs, we've moved out of the kitchen and into the cooler parts of the   
   house."   
       
   The Y dwarfs are in our sun's neighborhood, from approximately nine to 40   
   light-years away. The Y dwarf approximately nine light-years away, WISE   
   1541-2250, may become the seventh closest star system, bumping Ross 154 back   
   to eighth. By comparison, the star closest to our solar system, Proxima   
   Centauri, is about four light-years away.   
       
   "Finding brown dwarfs near our sun is like discovering there's a hidden house   
   on your block that you didn't know about," says Michael Cushing, a WISE team   
   member at JPL. "It's thrilling to me to know we've got neighbors out there yet   
   to be discovered. With WISE, we may even find a brown dwarf closer to us than   
   our closest known star."   
       
   Once the WISE team identified brown dwarf candidates, they turned to NASA's   
   Spitzer Space Telescope to narrow their list. To definitively confirm them,   
   the WISE team used some of the most powerful telescopes and spectrometers on   
   Earth to split apart the objects' light and look for telltale molecular   
   signatures of water, methane and possibly ammonia. For the very coldest of the   
   new Y dwarfs, the team used NASA's Hubble Space Telescope. The Y dwarfs were   
   identified based on a change in these spectral features compared to other   
   brown dwarfs, indicating they have a lower atmospheric temperature.   
       
   For more information about WISE, visit: http://www.nasa.gov/wise   
       
       
   Production Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   WISE -- mission home page   
       
   Credits:   
       
   Davy Kirkpatrick of Caltech is lead author of a paper appearing in the   
   Astrophysical Journal Supplement Series, describing the 100 confirmed brown   
   dwarfs.  Michael Cushing, a WISE team member at NASA's Jet Propulsion   
   Laboratory (JPL) in Pasadena, Calif., is lead author of a paper describing the   
   Y dwarfs in the Astrophysical Journal.   
       
   JPL manages WISE for NASA's Science Mission Directorate. The principal   
   investigator is Edward Wright at UCLA. The WISE satellite was decommissioned   
   in 2011 after completing its sky survey observations. The mission was selected   
   under NASA's Explorers Program managed by the Goddard Space Flight Center in   
   Greenbelt, Md. The science instrument was built by the Space Dynamics   
   Laboratory in Logan, Utah, and the spacecraft by Ball Aerospace and   
   Technologies Corp., in Boulder, Colo. Science operations and data processing   
   are at the Infrared Processing and Analysis Center at the California Institute   
   of Technology.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.64   
    * Origin: NCS BBS (1:3828/7)