Break out the cigars! Astronomers using the Spitzer Space Telescope have caught the first evidence that many—possibly most—binary stars hatch from the same cloud of dust, just as identical twins on Earth split from a single embryo. It turns out that some protostellar clouds, as they are called, often form irregular, elongated shapes instead of remaining spherical. Once that happens, it's much easier for the dust in the cloud to condense into two stars instead of one (six binary star systems in the making are shown above). Astronomers using Spitzer, whose infrared sensitivity can pierce the veil of dust and probe the starmaking process inside, found that 17 of the 20 protostellar clouds they peered into were considerably elongated. In addition, the other three clouds weren't quite spherical, either. And that may explain why most star systems in the Milky Way are binaries.
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