One of the biggest, baddest stars in our region of the galaxy is Antares. It's well to the left of the Moon at nightfall, and it shows a distinctly orange color. It's classified as a red supergiant -- a star that's much bigger and heavier than the Sun, and one that's doomed to blow itself apart as a supernova. There's only one other prominent red supergiant in our sky: Betelgeuse, which adorns winter nights.
To the northeast of Antares, though, in the nearby constellation Scutum, are two star clusters that together contain about 40 red supergiants. That's about one-fifth of the known red supergiants in the entire Milky Way galaxy.
The clusters are only a few hundred light-years apart, which may be a clue to why they contain so many supergiants. The clusters are near the edge of a fat "bar" of stars in the heart of the Milky Way. As the bar rotates, its gravity may squeeze big clouds of gas and dust outside the bar. The clouds collapse to form clusters of thousands of stars -- including the supergiants.
Both clusters are about 20,000 light-years from Earth. They're hidden behind vast clouds of dust, so they're not visible to the human eye. Astronomers discovered them through their infrared energy, which shines through the dust.
Red supergiants live no more than 10 million to 20 million years, then explode as supernovae. So like Antares, the stars in these clusters are doomed to blast themselves to bits.
Script by Damond Benningfield, Copyright 2008
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