Brown Dwarf Desert

StarDate: March 31, 2009

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The objects known as brown dwarfs have been described as a "missing link." They're big balls of gas that are heavier than planets, but not heavy enough to shine as stars. But their mass is enough to squeeze them tightly, heating them up and causing them to shine dull red.

But it turns out that these missing links are -- well, missing. Astronomers call this dearth of brown dwarfs the "brown dwarf desert."

Astronomers discovered the first brown dwarfs more than a decade ago, and they expected to find a lot more. But survey after survey has failed to turn up more than a handful of them. In fact, while astronomers have discovered more than 300 stars within about 30 light-years of Earth, they've found only a dozen brown dwarfs in that same volume of space.

Almost all of the brown dwarfs found so far are in binary systems -- they're gravitationally bound to a true star. Astronomers recently searched the most common types of stars -- the little cosmic embers known as red dwarfs -- for evidence of brown-dwarf companions. But a search of 233 stars revealed only two brown dwarfs -- and both of those were in a single star system.

The lack of brown dwarfs may mean that the universe simply doesn't like to make these in-between objects -- for whatever reason, it prefers to make either stars or planets. If that's the case, then no matter where we search, the missing links known as brown dwarfs will remain missing.

Script by Damond Benningfield, Copyright 2009

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