A galaxy is a huge mass of stars. The smallest galaxies contain about 100,000 stars the largest contain up to 3 billion stars.
There are three main types of galaxies according to what the shape of the galaxy looks like: Elliptical, which are oval shape; spiral, which have arms spiraling outward from a central bulge; and an Irregular, which have no organized shape. Sometimes, the shape of the of a galaxy is destroyed by a collision with another galaxy.
Ordinary galaxies are about 10 billion light years away. You can never see a galaxy, because they are too far away to see without a telescope.Think about it, you can't even see the planets, they're only a couple hundred thousand or even million miles away.
As far as galaxies go, M83 is a lot like the Milky Way. Like our home galaxy, it's about 100,000 light years in diameter, it shines at approximately the same brightness , and it's a spiral galaxy. So you could say that looking at M83's is a lot like looking at the Milky Way.
For more information visit the following sites:
http://school.discovery.com/schooladventures/universe/
