We have found two brown dwarf-sized masses around an ordinary star, which is very rare," said Alex Wolszczan, Evan Pugh professor of astronomy and astrophysics, Penn State and lead scientist on the project. The star, BD +20 2457, is a K2 giant -- an old bloated star nearing the end of its life. Seeing a pair of brown dwarfs around a K-type giant is a first for astronomers and offers a unique window into how they can be produced. The researchers from the ToruĊ Center for Astronomy, Poland and the Center for Exoplanets and Habitable Worlds, Penn State report their findings in the current issue of the Astrophysical Journal.
Brown dwarfs are dim, elusive objects that straddle the dividing line between planets and stars. They are too massive to be planets, but not massive enough to generate the fusion-powered energy of a star. These stellar cousins represent a kind of "missing link" between planets and stars, but little is known about how they are made.
"If we find one brown dwarf, we are not sure where it came from," Wolszczan explained. "It could be either from the process of planet formation or it could be a direct product of star formation."
Seeing two of them around a parent star means they must have originally formed from the enormous supply of raw materials that surrounded the star when it was young. Astronomers call this thick, solar system-sized pancake of gas and dust the "circumstellar disk."
"If that is the case," he continued, "then if we add up the minimum masses of these two objects, we know the disk had to be extremely massive."
by science daily
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