New cool stars

NASA announced last week the discovery of 14 of the coldest stars yet found. The “brown dwarfs” were discovered by the infrared space telescope Spitzer. (Incidentally yesterday marked the 2,500th day of the satellite’s mission.)

The stars represent bodies of gas that lack the mass to aggregate into nuclear furnaces. The newly discovered objects are between 450 Kelvin to 600 Kelvin (350 to 620 degrees Fahrenheit). This is the temperature of some planets.

NASA’s Wide-field Infrared Survey Explorer is now scanning a section of space 40 times larger than that analyzed by Spritzer, and by this means they are expecting to find numerous other similar bodies. NASA has even developed an artistic rendering with the simulated data of the predicted hundreds of failed stars.

“WISE is looking everywhere, so the coolest brown dwarfs are going to pop up all around us,” said Peter Eisenhardt, the WISE project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and lead author of a recent paper in the Astronomical Journal on the Spitzer discoveries. “We might even find a cool brown dwarf that is closer to us than Proxima Centauri, the closest known star.” (JPL Press Release, 6/24/10.)

According to the NASA press release:

Brown dwarfs form like stars out of collapsing balls of gas and dust, but they are puny in comparison, never collecting enough mass to ignite nuclear fusion and shine with starlight. The smallest known brown dwarfs are about 5 to 10 times the mass of our planet Jupiter — that’s as massive as some known gas-giant planets around other stars. Brown dwarfs start out with a bit of internal heat left over from their formation, but with age, they cool down. The first confirmed brown dwarf was announced in 1995.

“Brown dwarfs are like planets in some ways, but they are in isolation,” said astronomer Daniel Stern, co-author of the Spitzer paper at JPL. “This makes them exciting for astronomers — they are the perfect laboratories to study bodies with planetary masses.”

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