How Many Galaxies Are Believed to Exist?

Size

• According to Universe Today, in 2009 the best estimate of the number of galaxies is 100 to 500 billion.

Estimates

• From the Earth, we cannot see all of the universe. Therefore, to estimate the number of galaxies, astronomers look at a portion of the sky, estimate the number of galaxies in that portion, and then multiply by the inverse of the proportion examined. For example, if astronomers look at 1 percent of the sky, and find 2 billion galaxies, then they would multiply 2 billion by 100 to get 200 billion.

Theories/Speculation

• The estimates vary for a number of reasons. First, we have only examined a tiny portion of the sky. Second, as we examine each portion more closely, we find more galaxies. Third, most of the galaxies in the universe are tiny and may be hard to observe at the vast distances involved.