This is an artist rendition showing a cold brown dwarf, a small faint star-like object.
Credit: Penn State University/NASA/JPL-Caltech/J Williams

Brown dwarfs are dim relatively cool star-like objects, whose sizes and masses are intermediate between those of the smallest stars and the largest planets. Interestingly, they are described to be failed stars, as their masses are too low to ignite the nuclear fusion reactions, which transform hydrogen into helium, producing the enormous radiation of the stars. Also, brown dwarfs are typically reddish or magenta in color.

Two sophisticated spacecraft of the US space agency, NASA, recently discovered what appears to be the coldest known brown dwarf, which  is amazingly as cold as Earth's North Pole. These two space probes are the Wide-field Infrared Survey Explorer (WISE) and the Spitzer Space Telescope (SST), space-based observatories that explore the universe in infrared light.

The cold brown dwarf, technically known as WISE J085510.83-071442.5, lies 7.2 light-years away from our solar system, as estimated from WISE and SST images. This makes it the fourth closest system to the Sun. For comparison, the closest stellar system, known as Alpha Centauri, is about 4 light-years distant, and consists of three stars, orbiting each other.

WISE J085510.83-071442.5 has a frigid temperature between -48 to -13 degrees Celsius. Previous record holders for the coldest brown dwarf, also detected by WISE and SST, are much warmer, glowing at about room temperature.

Cool objects, such as brown dwarfs, may be too dim to be detected by optical telescopes, but they are bright in infrared images. Also, due to its nearness, the cold failed star appears to move rapidly across the sky.

While brown dwarfs are typically about 70 times more massive than Jupiter, the largest planet, WISE J085510.83-071442.5 is estimated to be only 3 to 10 times Jupiter’s mass. With such a low mass, it could be a Jupiter-like giant gaseous planet that drifts solitarily in space, probably after being ejected from a system of planets around a star. However, scientists estimate it is more likely a brown dwarf, since brown dwarfs are known to be fairly common in our Galaxy, the Milky Way. If so, it is also one of the least massive brown dwarfs known.

References
NASA
www.nasa.gov/ 
WISE Website
http://www.nasa.gov/wise
 
Aymen Mohamed Ibrahem
Senior Astronomy Specialist