Brown dwarf
Artist conception of WISE J085510.83-071442.5, the coldest known brown dwarf Penn State University/NASA/JPL-Caltech

Nasa has discovered what appears to be the coldest "brown dwarf" star-like body where temperatures fall to minus 48C - as cold as Earth's North Pole.

The Wide-field Infrared Survey Explorer (Wise) and Spitzer Space Telescopes discovered the dim object around 7.2 light-years away from Earth, earning it the title of the fourth closest system to our sun. The closest system, a trio of stars called Alpha Centauri, is approximately four light-years away.

"It's very exciting to discover a new neighbour of our solar system that is so close," said Kevin Luhman, an astronomer at Pennsylvania State University. "And given its extreme temperature, it should tell us a lot about the atmospheres of planets, which often have similarly cold temperatures."

The coldest brown dwarf is named Wise J085510.83-071442.5 and has a temperature ranging from minus 48 to minus 13C.

Brown dwarfs are substellar objects that begin their lives in the same way as stars, as collapsing balls of gas, but they lack the mass to burn nuclear fuel and radiate starlight.

The team said Wise was able to spot the star-like object because it surveyed the entire sky twice in infrared light. Cold objects such as brown dwarfs can be visible when viewed by visible-light telescopes, but their thermal glow - even if it is feeble - stands out in infrared.

"This object appeared to move really fast in the Wise data," said Luhman, as reported in the Tech Times. "That told us it was something special."

The fast motion of the brown dwarf attracted Luhman's attention in March 2013. Using Spitzer's infrared observations, he determined temperatures on the brown dwarf. The Gemini South Telescope in Chile was also used to study the object.

Combined detections from Wise and Spitzer, taken from different positions around the sun, enabled its distance to be measured through the parallax effect - the same phenomenon as making a finger "jump" if you hold it up to your face and look at it first with your left eye and then with your right.

"It is remarkable that even after many decades of studying the sky, we still do not have a complete inventory of the sun's nearest neighbours," said Michael Werner. Werner is the project scientist for Spitzer at Nasa's Jet Propulsion Laboratory, which manages and operates the telescope.

"This exciting new result demonstrates the power of exploring the universe using new tools, such as the infrared eyes of Wise and Spitzer," he added.

Wise J085510.83-071442.5 is estimated to be between three and 10 times the mass of Jupiter. With such a low mass, it could be a gas giant although scientists believe it is more likely to be a brown dwarf.

Werner told the Jaghran Post: "Despite its proximity to our solar system, the dwarf star is not an ideal destination for human space travel as any planets that might orbit it would be much too cold to support life as we know it."