NASA's Wise Mission Discovers Coolest Class of Stars

[NASA News <hqnews@xxxxxxxxxxxxxxxxxxxxxx>]

Aug. 23, 2011

Trent J. Perrotto 
Headquarters, Washington                                     
202-358-0321 
trent.j.perrotto@xxxxxxxx 

Whitney Clavin 
NASA's Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-4673 
whitney.clavin@xxxxxxxxxxxx 
RELEASE: 11-274

NASA'S WISE MISSION DISCOVERS COOLEST CLASS OF STARS

WASHINGTON - Scientists using data from NASA's Wide-field Infrared 
Survey Explorer (WISE) have discovered the coldest class of star-like 
bodies, with temperatures as cool as the human body. 

Astronomers hunted these dark orbs, termed Y dwarfs, 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 six 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," said Jon Morse, Astrophysics Division director at NASA 
Headquarters in Washington. "They are 5,000 times brighter at the 
longer infrared wavelengths WISE observed from space than those 
observable from the ground." 

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. 

Astronomers study brown dwarfs to better understand how stars form and 
understand the atmospheres of planets beyond our solar system. 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. More discoveries 
are expected as scientists continue to examine the enormous quantity 
of data from WISE. 

The telescope performed the most advanced survey of the sky at 
infrared wavelengths to date, from Jan. 2010 to Feb. 2011, scanning 
the entire sky about 1.5 times. 

Of the 100 brown dwarfs, 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). 

"The brown dwarfs we were turning up before this discovery were more 
like the temperature of your oven," said Davy Kirkpatrick, a WISE 
science team member at the Infrared Processing and Analysis Center at 
the California Institute of Technology in Pasadena, Calif. "With the 
discovery of Y dwarfs, we've moved out of the kitchen and into the 
cooler parts of the house." 

Kirkpatrick 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. 

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," Cushing said. 
"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 
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. 

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. For more information about WISE, visit: 



http://www.nasa.gov/wise 

	
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