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Winter Milky Way III

February 17, 2012

Because we’re inside the disk of the Milky Way, we can’t see our home galaxy’s most beautiful features — its shimmering spiral arms. From outside, they’d make the Milky Way look like a swirling pinwheel, with great streamers of stars wrapping around a “bar” of stars in the middle.

The space between the spiral arms isn’t empty, though. Those regions also contain lots of stars. But the spiral arms are home to the brightest stars — vigorous youngsters that live short, radiant lives, then blow themselves to bits. They form as a wave races around the galaxy, squeezing vast clouds of gas and dust to give birth to new stars.

Some examples of these hot young stars are found in the spiral arm that’s outward from our own location in the galaxy. It’s known as the Orion Arm because it contains many of the brilliant stars of Orion, the hunter.

The brightest are Betelgeuse and Rigel — an orange supergiant and a blue supergiant. Both of them are several hundred light-years away, yet they produce so much light that they’re among the dozen brightest stars in the night sky. And the stars that line up between them — the three stars of Orion’s Belt — are just as impressive. Like Betelgeuse and Rigel, they’re doomed to explode as supernovae — briefly adding to the brilliance of the Orion Arm.

Orion is high in the south at nightfall. Betelgeuse and Rigel form opposite corners of a large rectangle, with Orion’s Belt at its center.


Script by Damond Benningfield, Copyright 2011


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