OB association
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What Are Spiral Arms?
Probably the most spectacular feature of our Milky Way galaxy is its spiral arms. We can’t get a probe far enough out yet to take a galactic selfie, but astronomers are reasonably sure that we live in a spiral galaxy.…
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Observations of Star Birth
Astronomers have a pretty solid idea of how stars are born. They begin within the dense, cold dust of an interstellar cloud such as this one. They heat up and get more luminous as they contract, and then drop in…
