Counting Clouds

StarDate: August 9, 2010

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One of the highlights of the summer sky is the Milky Way -- the glowing band of light that outlines the disk of our home galaxy. Under a dark sky, it arcs high across the east as darkness falls tonight, from W-shaped Cassiopeia in the north to teapot-shaped Sagittarius in the south.

As you watch the Milky Way, you'll notice that it isn't even and smooth. Instead, its edges are irregular, and it's strewn with dark patches. These patches are giant clouds of gas and dust that absorb the light of more-distant stars. Some of them may someday give birth to new stars.

Such stellar nurseries are sprinkled throughout the galaxy. In fact, a recent survey found dozens that had never been seen before. Some are at the galaxy's edge, while others are at the edge of the giant bar of stars at the Milky Way's center.

Astronomers used radio telescopes to find giant clouds of hydrogen gas that have given birth to hot, heavy stars. Such stars produce a lot of radiation. The energy strips electrons from the surrounding hydrogen atoms, causing them to produce radio waves.

Such gas clouds probably aren't through giving birth to stars. Some of them have enough gas to spawn dozens of stars as massive as the Sun.

The researchers are mapping other regions of the galaxy, and expect to find hundreds more big clouds -- clouds that are adding to the Milky Way's already hefty population of stars.

More about the Milky Way's gas clouds tomorrow.

Script by Damond Benningfield, Copyright 2010

For more skywatching tips, astronomy news, and much more, read StarDate magazine.

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