Scientists using data from NASA's Wide Field Infrared Survey Explorer (WISE) spacecraft have discovered the coldest class of star-like objects, brown dwarfs with temperatures as cool as the human body. Brown dwarfs are small faint objects, known as failed stars, since they do not evolve into normal stars. Stars shine by burning hydrogen within their cores, through nuclear fusion reactions, while brown dwarfs have masses that are too low to sustain these reactions.
Astronomers have searched for these feeble brown dwarfs, termed Y dwarfs, for more than a decade, without success. When observed with a visual-light telescope, they are almost invisible. However, WISE's infrared detectors allowed to finally spot the dim glow of six Y dwarfs, within a distance of about 40 light-years from the Sun. The Y dwarfs are the coldest brown dwarfs, which cool and fade with time, eventually emitting infrared mostly.
"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.
The atmospheres of brown dwarfs are similar to the atmosphere Jupiter, a gas-giant planet. Astronomers study brown dwarfs for a better understanding of star formation, and the processes occurring in the atmospheres of giant planets, orbiting beyond our Solar System.
One of the newly identified Y dwarfs, termed WISE 1828+2650, is the record holder for the coldest brown dwarf, with an estimated atmospheric temperature cooler than room temperature, or less than about 25 degrees Celsius.
So far, WISE data have uncovered 100 new brown dwarfs. More discoveries are expected, as scientists continue to examine WISE’s treasures of data. The spacecraft conducted the most advanced ever survey of the sky at infrared, between January 2010 and February 2011.
References and Further Reading
http://www.nasa.gov/wise
http://wise.astro.ucla.edu
http://jpl.nasa.gov/wise
Wikipedia