How Many Galaxies Are There?

Scattered throughout the universe are vast islands of stars, called galaxies. Our sun is a star in the Milky Way galaxy. This is our galaxy, too, and it has billions of stars in it. It takes light about one hundred thousand years, to go from one end of our galaxy to the other (and light travels about six million million miles in one year !)

Astronomers have discovered through the use of telescopes that there are millions of galaxies beyond our own. There are basically three types of galaxies that we know about. Those that have a spiral shape (like our own Milky Way) are called spiral galaxies. The one nearest to us is about two million light-years away. It is the great spiral galaxy in the constellation Andromeda.

About 17 per cent of the brightest galaxies that have been ob­served are called elliptical galaxies. (An ellipse is like a stretched-out circle.) These galaxies contain mostly stars and seem to have little or no dust and gas.

Some galaxies are called irregular galaxies because they appear to have no special shape. These galaxies contain stars, dust, and gas. The two galaxies nearest the Milky Way are irregular galaxies.

There are also some small galaxies that are called dwarf galaxies. The smallest are only a few hundred light-years across and contain only a few thousand stars. There may be more dwarf galaxies in the universe than larger ones.

Galaxies are separated from one another by hundreds of thousands of light-years. They usually occur in groups or clusters containing from several tens to many thousands of galaxies.

The most distant clusters of galaxies so far observed lie billions of light-years from our Milky Way. And there are galaxies so far away. from us that it is almost impossible for us to imagine the vastness of the distance. So the answer to the question of how many galaxies there are in the universe will probably always remain a mystery.