'Coldest ever' star spotted just beyond our solar system - and it could be as frosty as Earth's North Pole
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A brown dwarf star that appears to be the coldest of its kind - as frosty as Earth's North Pole - has been spotted by an American astronomer.
The discovery was made using Nasa's Wide-field Infrared Survey Explorer (WISE) and the Spitzer Space Telescope.
Images from the space telescopes also pinpointed the object's distance at 7.2 light years away, making it the fourth closest system to our sun.
A star as cold as Earth's North Pole has been discovered 7.2 light years away. The chilly brown dwarf, which would be the fourth closest system to our sun, was spotted by Nasa's WISE telescope and the Spitzer Space Telescopes (artist's impression of the star shown)
'It is very exciting to discover a new neighbour of our solar system that is so close,' said Kevin Luhman, an associate professor of astronomy and astrophysics at Penn State and a researcher in the Penn State Center for Exoplanets and Habitable Worlds.
'In addition, its extreme temperature should tell us a lot about the atmospheres of planets, which often have similarly cold temperatures.'
Brown dwarfs start their lives like stars, as collapsing balls of gas, but they lack the mass to burn nuclear fuel and radiate starlight.
The newly-found brown dwarf, named Wise J085510.83-071442.5, is thought to have a chilly temperature between -48°C to -13°C (-54°F to 9°F).
Previous record holders for coldest brown dwarfs, also found by WISE and Spitzer, were about room temperature.
Although it is very close to our solar system, Wise J085510.83-071442.5 is not an appealing destination for human space travel in the distant future.
'Any planets that might orbit it would be much too cold to support life as we know it,' Luhman said.
'This object appeared to move really fast in the Wise data,' said Luhman.
'That told us it was something special.'
The closer a body, the more it appears to move in images taken months apart.
Above you can see how the star was tracked over two periods by the WISE and Spitzer telescopes
Airplanes are a good example of this effect: a closer, low-flying plane will appear to fly overhead more rapidly than a high-flying one.
WISE was able to spot the rare object 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 - even if feeble - stands out in infrared light.
After noticing the fast motion of Wise J085510.83-071442.5 in March, 2013, Luhman spent time analysing additional images taken with Spitzer and the Gemini South telescope on Cerro Pachon in Chile.
Spitzer's infrared observations helped to determine the frosty temperature of the brown dwarf.
THE SPITZER TELESCOPE
Spitzer is designed to detect infrared radiation, which is primarily heat radiation.
Its highly sensitive instruments allow scientists to peer into cosmic regions that are hidden from optical telescopes, including dusty stellar nurseries, the centres of galaxies and newly forming planetary systems.
The telescope's infrared 'eyes' also allows astronomers see cooler objects in space, like failed stars, extrasolar planets, giant molecular clouds and organic molecules that may hold the secret to life on other planets.
Spitzer was launched on August 25, 2003 and was designed to have a lifespan of at least two-and-a-half years.
Over the past decade Spitzer has taken over two million images of the Milky Way, which have now been stitched together to create the panorama.
It has spent 172 days or 4,142 hours taking pictures of the 'disk' or plane of the Milky Way in infrared light.
Wise J085510.83-071442.5 is estimated to be three to 10 times the mass of Jupiter.
With such a low mass, it could be a gas giant similar to Jupiter that was ejected from its star system.
But scientists estimate it is probably a brown dwarf rather than a planet since brown dwarfs are known to be fairly common.
Combined detections from WISE and Spitzer, taken from different positions around the sun, enabled the measurement of its distance through the parallax effect.
This is the same principle that explains why your finger, when held out right in front of you, appears to jump from side to side when you alternate left-eye and right-eye views.
Wise 0855 is the fourth closest stellar system to our sun, although it is not thought to either be habitable itself or able to host any habitable planets. However, its discovery suggests there could be more such 'hidden' brown dwarfs lurking near us that are waiting to be discovered
In March of 2013, Luhman's analysis of the images from WISE uncovered a pair of much warmer brown dwarfs at a distance of 6.5 light years, making that system the third closest to the Sun.
His search for rapidly moving bodies also demonstrated that the outer solar system probably does not contain a large, undiscovered planet, which has previously been referred to as 'Planet X' or 'Nemesis.'
'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 neighbors,' said Michael Werner, the project scientist for Spitzer at Nasa's Jet Propulsion Laboratory (JPL), which manages and operates Spitzer.
'This exciting new result demonstrates the power of exploring the universe using new tools, such as the infrared eyes of WISE and Spitzer.'
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