Cool Star is a Gem of a Find

Feature Nov. 09, 2010

Cool Star is a Gem of a Find

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-377&cid=release_2010-377

NASA's Wide-field Infrared Survey Explorer, or WISE, has eyed its first cool brown
dwarf: a tiny, ultra-cold star floating all alone in space.

WISE is scanning the whole sky in infrared light, picking up the glow of not just brown
dwarfs but also asteroids, stars and galaxies. It has sent millions of images down to Earth,
in which infrared light of different wavelengths is color-coded in the images.

"The brown dwarfs jump out at you like big, fat, green emeralds," said Amy Mainzer, the
deputy project scientist of WISE at NASA's Jet Propulsion Laboratory in Pasadena,
Calif. Mainzer, who makes jewelry in her spare time, explained that the brown dwarfs
appear like green gems in WISE images because the methane in their atmospheres absorbs
the infrared light that has been coded blue, and because they are too faint to give off the
infrared light that is color-coded red. The only color left is green.

Like Jupiter, brown dwarfs are made up of gas -- a lot of it in the form of methane,
hydrogen sulfide, and ammonia. These gases would be deadly to humans at the
concentrations found around brown dwarfs. And they wouldn't exactly smell pretty.

"If you could bottle up a gallon of this object's atmosphere and bring it back to Earth,
smelling it wouldn't kill you, but it would stink pretty badly -- like rotten eggs with a hint
of ammonia," said Mainzer.

Mainzer and other members of the WISE team are already accumulating a quarry of
brown dwarf candidates similar to this one. Brown dwarfs have masses somewhere
between those of a star and a planet. They start out like stars as collapsing balls of gas,
but they lack the mass to fuse atoms together at their core and shine with starlight. As
time goes on, these lightweights cool off, until they can only be seen in infrared light.

There could be many such objects lurking in the neighborhood of our sun, but
astronomers know of only a handful so far. WISE is expected to find hundreds, including
the coolest and closest of all.

To scientists, brown dwarfs represent the perfect laboratories for studying planet-like
atmospheres.

"They're a great test of our understanding of atmospheric physics of planets, since they
don't have solid surfaces, and there's no big, bright sun to get in the way," said co-author
Michael Cushing, a postdoctoral fellow at JPL.

WISE's new brown dwarf is named WISEPC J045853.90+643451.9 for its location in
the sky. It is estimated to be 18 to 30 light-years away and is one of the coolest brown
dwarfs known, with a temperature of about 600 Kelvin, or 620 degrees Fahrenheit. That's
downright chilly as far as stars go. The fact that this brown dwarf jumped out of the data
so easily and so quickly -- it was spotted 57 days into the survey mission -- indicates that
WISE will discover many, many more. The discovery was confirmed by follow-up
observations at the University of Virginia's Fan Mountain telescope, the Large Binocular
Telescope in southeastern Arizona, and NASA's Infrared Telescope Facility on Mauna
Kea, Hawaii. The results are in press at the Astrophysical Journal.

Read more about how NASA's Spitzer Space Telescope and WISE are hunting down the
coldest brown dwarfs here http://www.jpl.nasa.gov/news/news.cfm?release=2010-210 .

JPL manages the Wide-field Infrared Survey Explorer for NASA's Science Mission
Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The
mission was competitively selected under NASA's Explorers Program managed by the
Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the
Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball
Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing
take place at the Infrared Processing and Analysis Center at the California Institute of
Technology in Pasadena. Caltech manages JPL for NASA. More information is online at
http://www.nasa.gov/wise and http://wise.astro.ucla.edu .

-end-

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
Whitney.clavin@jpl.nasa.gov

To remove yourself from this mailing, please go to http://www.kintera.org/TR.asp?a=hhKNI2OKLiIPKaJ&s=dnIOLMOlG9JAILPrEnF&m=9gJQIYPzFkITJaL

To remove yourself from all mailings from NASA Jet Propulsion Laboratory, please go to http://www.kintera.org/TR.asp?a=kuITJbPWKlLWIkI&s=dnIOLMOlG9JAILPrEnF&m=9gJQIYPzFkITJaL