A computer simulation could be the key to understanding how spiral galaxies, including the Milky Way, get and maintain their unique arms. The spiral arms, long believed to be a fleeting feature, are actually "self-perpetuating, persistent, and surprisingly long lived," said Mark Vogelsberger, from the Harvard-Smithsonian Center for Astrophysics. Researchers say their findings suggest that large molecular clouds help form the spiral arms. Once formed, the galaxy is capable of maintaining them indefinitely.
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