U.S. astronomer using NASA’s Wide-field Infrared Survey Explorer and Spitzer Space Telescope has discovered WISE J085510.83-071442.5 (WISE 0855-0714 for short) – the fourth closest system to our Sun and the coldest brown dwarf yet seen in the known Universe.

WISE 0855-0714 is estimated to be 3 to 10 times the mass of Jupiter and has a chilly temperature between minus 48 to minus 13 degrees Celsius.

With such a low mass, the object could be a gas giant that was ejected from its star system. But astronomers estimate WISE 0855-0714 is probably a brown dwarf rather than a planet since brown dwarfs are known to be fairly common.

At a distance of about 7.2 light-years away from Earth, this object is the fourth closest system to us, after Alpha Centauri AB – Proxima Centauri, Barnard’s Star and WISE 1049-5319 (also known as Luhman 16AB).

“It is very exciting to discover a new neighbor of our Solar System that is so close. In addition, its extreme temperature should tell us a lot about the atmospheres of planets, which often have similarly cold temperatures,” said Dr Kevin Luhman from the Pennsylvania State University, the author of a paper published in the Astrophysical Journal Letters (arXiv.org version).

“This object appeared to move really fast in the data from NASA’s Wide-field Infrared Survey Explorer (WISE). That told us it was something special.”

WISE was able to spot WISE 0855-0714 because it surveyed the entire sky twice in infrared light, observing some areas up to three times. Cool objects like brown dwarfs can be invisible when viewed by visible-light telescopes, but their thermal glow stands out in infrared light.

After noticing the fast motion of WISE 0855-0714 in March, 2013, Dr Luhman spent time analyzing additional images taken with Spitzer and the Gemini South telescope in Chile.

Spitzer’s infrared observations helped to determine its temperature. Combined detections from WISE and Spitzer, taken from different positions around the Sun, enabled the measurement of its distance through the parallax effect.

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K.L. Luhman. 2014. Discovery of a ~250 K Brown Dwarf at 2 pc from the Sun. ApJ 786, L18; doi: 10.1088/2041-8205/786/2/L18