A brown dwarf star, with a surface temperature equal to that of the North Pole, is the coldest such body ever discovered by astronomers. The newly-discovered star is also one of the closest, laying less than twice the distance to Alpha Centauri.
Kevin Luhman, an associate professor of astronomy and astrophysics at Penn State, discovered the frigid star using images from the WISE satellite and the Spitzer Space Telescope. The Wide-field Infrared Survey Explorer (WISE) observatory launched in 2009, and went into hibernation following a transmitter failure in 2011. Spitzer has been carrying out observations wince it reached orbit in 2003.
The star, given the designation WISE J085510.83-071442.5, is just 7.2 light years away from the sun, making it the fourth-closest stellar body to our home system.
"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," Luhman said.
The WISE observatory detected the star in infrared images taken of the region of sky where the star is located. All objects with temperatures from Arctic temperatures up to tens of thousands of degrees emit infrared radiation. The exact wavelength of this emission is dependent on its surface temperature. Measuring differences in these frequencies is the basis of many night-vision systems.
Despite the relative closeness of the brown dwarf to our own sun, the location is unlikely to become a tourist destination in a future when humans travel from star-to-star.
"Any planets that might orbit it would be much too cold to support life as we know it," Luhman said in a press release.
Surface temperatures on the star range from -54 to 9 degrees Fahrenheit. Before this discovery, the coldest brown dwarfs known were measured to have surfaces with room temperatures. It is believed to have a mass of between three and 10 times greater than Jupiter, making the object one of the smallest brown dwarfs ever discovered.
The failed star was seen to move a great deal in different images taken by WISE, telling Luhman the star was close to the sun.
"This [parallax] 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- and right-eye views," NASA officials wrote in a press release about the discovery.
This discovery led the astronomer to continue his study of WISE J085510.83-071442.5 by examining images taken by the Spitzer space telescope, as well as the Gemini South Telescope, located in Chile.
Brown dwarfs start to coalesce out of gas, like larger stars. But these bodies fail to gather enough material to ignite nuclear fusion. This keeps them from igniting with the light and heat of an ordinary star.
