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When you look at the night sky, all the stars you see are a small part of our own Milky Way galaxy. The Milky Way is a spiral galaxy, and the sun is located about 30,000 light-years from the Milky Way’s nucleus on the Orion arm. If you see a creamy strip across the sky on a moonless night, you’re looking out at the outer edge of the Milky Way. (If you lived in the southern hemisphere, you’d be looking into the center of the Milky Way.)
Like all galaxies, the Milky Way is held together by gravity. This gravity also holds the stars, gas, and dust in orbit around the center of the galaxy. Just as the planets orbit around the sun, the sun orbits around the center of the Milky Way. Of course, it’s a long trip around—about 225 million years!
Answers From the Expert
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Frank Summers, American Museum of Natural History
Questions:
• What is happening in the center of the Milky Way?
