Galaxies: the Star Cities of the Universe

Imagine looking down from an aeroplane at night and seeing thousands of lights: windows, car headlights and signs. That is what a large city looks like from above.

Stars also gather into enormous cities in space. Each of these “cities” is called a galaxy.

A single galaxy contains billions of stars.

Gravity binds all of them together.

Our galaxy is called the Milky Way. It looks like an enormous sparkling spiral. From Earth, we see only its edge: a hazy band of light stretching across the sky.

There are many other galaxies too.

Some galaxies even collide. Right now, somewhere in the Universe, two galaxies are slowly approaching each other. They do not smash apart; they pass through one another or merge into one enormous galaxy.

How Many Galaxies Are There?

Scientists counted for a long time and estimate that the Universe contains about two hundred billion galaxies: 200,000,000,000—far too many to count one by one.

If every galaxy is a star city containing billions of stars, imagine how many stars there are altogether. There may be more of them than grains of sand on all Earth’s beaches.

Now you can see just how vast space is—truly beyond measure.