On A Clear Night

How far can the unaided eye see? On a clear night, about 2.5 million light years. That's the distance to the Andromeda Galaxy, the farthest object in space that can be seen without artificial means. 

It's easiest to see Andromeda later this summer, when it rises earlier in the night. Remind me to point it out so that you can find it. The bulge of the galaxy covers a spot in the sky the size of the full moon. The entire galaxy—if we could see it all with just our eyes—would cover the sky the length of eight full moons. But the apparent light is so faint that all we can observe unaided is the central bulge. Because of its size, binoculars are a great way to view Andromeda. It will look like a large fuzzy snowball, faint and gray. 

Remember, you will never witness any view with or without a telescope like the fantastic images you've seen everywhere. That's because the human eye only sees in "real time;" we cannot store information like a computer or film and allow it to accumulate. Because machines can do that, they give us a far more detailed picture, aided by false color assignments to designate certain wavelengths of elements present.

In the photo below, every point of light is a star in our own galaxy. (In fact, all stars we see in visible light are in our galaxy. It takes a different kind of 'scope to "see" distant stars in extreme wavelengths.) The two small fuzzy ovals are satellite galaxies, performing a slow-motion dance of collision with Andromeda. This photo comes courtesy of Astronomy Picture of the Day, and this is today's picture. Happy Mother's Day!