ScienceMag.org - 6/6/13,
Building a planet seems straightforward enough: Just take a disk of dust swirling around a young star, and let it sit. Micron-sized dust particles will collide and clump together, growing in size, until eventually, voilà! One planet. There's a problem, however: Astrophysicists have calculated that once clumps have reached a certain size, collisions with other clumps should smash them to smithereens. Or they should start drifting inward toward the star, where they can't grow further. How then can planets even form?
Astronomers who've imaged the dust disk spinning around a young star 390 light-years from Earth may have found an answer. Viewing the star using the newly unveiled Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile, the researchers observed a crescent-shaped vortex of gas in the disk that appears to provide a safe haven in which a planetary seed can continue to grow. The vortex essentially creates a dust trap within which large clumps can get larger while avoiding drifting inward long enough to form the rocky core of a planet.
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