Coolest Star Ever Detected

The key to confirming that CFBDS0059 or any other cool brown dwarf is a Type Y would be the presence of ammonia in its atmosphere, Albert explained. To find that requires gathering lots of infrared light, splitting it into its spectrum and looking for telltale dark lines where ammonia gas is absorbing light.

"We are starting to see a little hint of ammonia absorption," Albert told Discovery News.

Other brown dwarf researchers are confident that ammonia is showing up, but are less sure it warrants a new class of dwarfs.

"It really depends on what is decided to define this class," said Adam Burgasser of the Massachusetts Institute of Technology.

The two verified classes of brown dwarfs, L and T dwarfs, are not subtle about their differences. L Dwarfs are much hotter, reaching between 2,200 and 3,600 degrees F (1,200 and 2,000 degrees C). T dwarfs are cooler than 2,190  degrees F (1,200 degrees C) and rich in methane.

It's likely, says Burgasser, that as more of these even cooler dwarfs are found, there likely will be some that are a couple of hundred degrees cooler than CFBDS0059. That means any water in there atmospheres will condense into droplets of water vapor, which would make these dwarfs dramatically different than their L and T dwarf brothers.

In brown dwarf atmospheres, water is generally in gaseous state, while in giant planets it condenses into water ice. So an even cooler dwarf would truly be on the verge of being more of a hot, giant Jupiter than a star.

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