Interstellar Clouds And Dark Nebulae

... Look for dark interstellar clouds blocking patches of Milky Way stars! What's up for July 2010: Dark Nebulae in the Milky Way Galaxy ... with Jane Houston Jones at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

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We live in the Milky Way Galaxy. If you were looking down on the Milky Way, it would look like a large pinwheel rotating in space. Our Galaxy is a spiral galaxy that formed approximately 14 billion years ago. Contained in the Milky Way are stars, clouds of dust and gas called nebulae, planets, and asteroids. Stars, dust, and gas fan out from the center of the Galaxy in long spiraling arms. The Milky Way is approximately 100,000 light-years in diameter. Our solar system is 26,000 light-years from the center of the Galaxy. All objects in the Galaxy revolve around the Galaxy's center. It takes 250 million years for our Sun (and the Earth with it) to make one revolution around the center of the Milky Way.

When you look up at the night sky, most of the stars you see are in one of the Milky Way arms. Before we had telescopes, people could not see many of the stars very clearly. They blurred together in a white streak across the sky. A myth by the ancient Greeks said this white streak was a "river of milk". The ancient Romans called it the Via Galactica, or "road made of milk". This is how our Galaxy became known as the Milky Way. It is interesting to note that astronomers capitalize the "G" in galaxy when talking about our Milky Way!

Today, astronomers have been able to observe the Milky Way in all regions of the electromagnetic spectrum. They have had to be clever in making the observations since they are having to look through the disk of the Galaxy from our location in one of the arms! Below, you can see that the Milky way looks very different in different wavelengths of light. You can read more about this at the Multiwavelength Milky Way Web site.

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