How Many Stars are in Galaxies? | Universe Today

Written by Fraser Cain

As you probably know, galaxies aren't individual objects, but vast groupings of stars. In fact, "vast" isn't a big enough word to describe how many stars there are in galaxies. So, how many stars are in galaxies?

Well, that question depends on the type of the galaxy. The smallest galaxies are called dwarf galaxies. They're too small to form the vast spiral shape that we see in galaxies like the Milky Way and Andromeda. A dwarf galaxy can have as few as 10 million stars. These dwarf galaxies are constantly being absorbed into larger and larger galaxies.

Our own Milky Way is a spiral galaxy. These are much more massive than the relatively tiny dwarf galaxies, and contain hundreds of billions of stars. For example, the Milky Way contains 200 billion stars – 200,000,000,000 stars. The nearby Andromeda galaxy is much more massive than the Milky Way and contains 1 trillion stars; 5 times as many stars as the Milky Way.

The largest galaxies in the Universe are known as ellipticals. These enormous galaxies have lost their spiral shape through many interactions between large galaxies. They're found at the cores of the largest galaxy clusters. The biggest galaxy ever discovered is inside the Abell 2029 cluster and contains 100 trillion stars. That's 100,000,000,000,000 stars.

And just think, there are 100 billion galaxies in the observable Universe. When you put those numbers together, you get an estimate of 10²⁴ stars in the entire Universe. Or a 1 followed by 24 zeroes. That's 1,000,000,000,000,000,000,000,000 stars.

We have written many articles about stars on Universe Today. Here's an article about how many stars there are in the Milky Way. And here's an article about the largest structure in the Universe.

Want more information on stars? Here's NASA's World Book on Stars, and more information from NASA's imagine the Universe.

We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

Filed under: Astronomy