How Big Is the Milky Way Galaxy?

The distance our solar system travels to complete one lap around the Milky Way galaxy is nearly 2 billion times the distance the Earth travels around the Sun. Wow!

Jason Marshall, PhD,
January 10, 2012

This week’s number, 1.608x1018 km, is a big number. Which makes perfect sense since this week's Math Dude article is about how to read and write big numbers using scientific notation.

If you need a scientific notation refresher, I encourage you to check out that article. But all you really need to know to appreciate the immensity of this number is that:

1.608x1018 km = 1,608,000,000,000,000,000 km

Which, obviously, is a lot of kilometers! What exactly is this distance? It’s the distance that the Solar System (within which we happily reside) travels as it completes one lap around the Milky Way galaxy.

That's right—just as the Earth travels around the Sun, the Solar System travels around and around the galaxy…and it travels a long way in doing so. For comparison, this distance is nearly 2 billion times further than the distance that Earth travels around the Sun each year.

Moving at the rather impressive speed of ~220 km/s, it takes the Solar System a total of about 225 million years—or 2.25x108 years in scientific notation—to complete its orbit. That's both a long way and a long time. So enjoy the ride!

Image courtesy of Shutterstock