Astronomers Have Discovered A Star That's As Cold As Ice- Close To Our System

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Photo Credit: Robert Hurt/JPL, Janella Williams/Penn State University

Our sun has a new neighbor, one so faint we have not detected it earlier, although being the fourth neighboring system to our own Sun. In addition to its importance from being so close by, the new discovered object is also the coolest one of its group ever detected.

Brown dwarfs fill the space between the smallest stars and large planets. They start out disintegrating from patches of gas just as stars do, but they never get large enough to start fusion of normal hydrogen. Although they do produce a little heat from fusing small quantity of deuterium, and in some circumstances lithium, their key source of high temperature is from the gravitational collapse. This gradually expires away with time, and the deuterium burning also runs out in period measured in millions years, rather than billions of years.

Janella Williams, Penn State University. The four nearest star systems to our own, with the year in which their distance was first measured

A very weird object called WISE J085510.83-071442.5 lies just 7.2 light-years away from the earth. This object was discovered by the Wide-field Infrared Survey Explorer (WISE), it is technically one of those not-quite-planets-not-quite-stars identified as a brown dwarf.

Since they are so much minor and chiller than stars, brown dwarfs appear red and faint. But astronomer Kevin Luhman observed that WISE J085510.83-071442.5 was very faint and very red, partly because it is small, possibly only 2 to 10 times to the mass of Jupiter and partially because it is so cold. According to Luhman its temperature is only around 9° F (-13° C). That's well beneath the freezing point of water. So in other words, the brown dwarf is plainly ice cold. The statement that it is so cold is a sign to its age. If it started out at a few thousand degrees it would have taken anywhere among 1 and 10 billion years to have cooled to its current temperature.

This new sighting was made by Associate Professor Kevin Luhman of Penn State University, using the NASA's Wide-field Infrared Survey Explorer and declared in The Astrophysical Journal. Luham is examining images taken by WISE for objects that have relocated between observations. If an object is close it will seem to travel beside the background stars as the Earth moves from one side of the sun to the other, and is also possible to appear to be moving from year to year much quicker than something more distant.

WISE J085510.83-071442.5 has mass low enough to increase complicated questions of classification. Current approximations are 3-10 times the mass of Jupiter. Meanwhile some definitions hold that objects need be at least 10 Jupiter masses to get the label of Brown dwarf it may ultimately find itself downgraded in the records, just as Pluto was. Nonetheless, whereas it is imaginable this is a large planet that was expelled from its solar system at some point, it is considered more likely to have made on its own, sufficient to earn brown dwarf status on other definitions.

Observations of WISE J085510.83-071442.5 by the WISE and Spitzer telescopes expose the quick motion of the brown dwarf over the past four years. Photo by NASA/JPL-Caltech/Penn State]

It is only a year since the third nearby star system turned up 6.5 light years away, two brown dwarfs also discovered by Luhman, and currently dubbed Luhman 16. It is now well understood that our area of space is much more crowded than we recognized.

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