How Far can you See?

But if you look up, you can see for about 150 million kilometers! That's how far away the Sun is. If you wait a few hours for nightfall, you'll see a lot farther. Saturn, the farthest planet from the Earth easily visible to the unaided eye, is about a billion kilometers away on average. But even that is closeby compared to the stars. The nearest star is 4 light years, or 40 trillion kilometers away. Betelgeuse, the bright red star that marks Orion's shoulder, is about 400 light years, or 4 quadrillion kilometers away (that's a 4 followed by 15 zeroes!).

But even that is small change. The Andromeda Galaxy, a collection of billions of stars much like our own Milky Way Galaxy, is not hard to see with the naked eye from a dark spot on a winter night, and it is 2.9 million light years away. That's about 20 million million million kilometers away, or a 2 followed by 19 zeroes!

So on a clear day, you can see quite a ways, but on a clear night, you almost can see forever.

Thanks to Bitesize Reader Troy Hoffman for pointing out I had written `miles' at one point on this page instead of `kilometers'. Also, thanks to regular Bad Reader Russ Bogel for pointing out that I had an old distance to the Andromeda Galaxy listed. The new distance of 2.9 million light years came out after the Hipparcos satellite made better distance measurements to nearby stars.