Have you ever seen a galaxy? You can! Just look up on a moonless night. All the stars you see are part of the Milky Way galaxy. We live in the “suburbs,” or outskirts, of this galaxy, which is made up of about 200 billion stars. The Milky Way’s central core looks like a creamy stream across the black sky. (Galaxias is the Greek word for “milky.”) That “creamy stream” is really billions of stars.
A galaxy is a huge swarm of stars, gas, dust, and dark matter held together by gravity. Stars revolve around the center of a galaxy. The galaxy’s gravity holds them in their orbits. A galaxy’s center is packed with older stars. The distance between stars is enormous, however. Proxima Centauri, the nearest star to our Sun, is about 25 trillion miles away! Powerful telescopes show us there are billions of galaxies in the universe, with the largest holding thousands of billions of stars. What other bodies “swim” in galaxies? How do galaxies form? New technology is helping astronomers find answers and raise questions about our universe.
