"

189 A Spinning Spiral

The Milky Way Galaxy rotates, undergoing what is known as differential rotation: everything rotates at about the same speed. This type of rotation is different than a rotating tire. Our Sun and Solar System orbits around the Milky Way Galaxy once every 230 million years. Observing the Milky Way Galaxy’s rotation helps astronomers determine where the galaxy’s mass is located.Collision Alert!

Current observations show that the Andromeda Galaxy is approaching the Milky Way Galaxy at 100 to 140 kilometers/second. It appears as if a collision may occur in 3 to 4 billion years. If Andromeda Galaxy and Milky Way Galaxy collide, individual stars within the galaxies would not collide, but instead the two galaxies will merge to form a single elliptical galaxy over the course of about a billion years.

An artist’s illustration of the Milky Way Galaxy— elegant bluish spiral structure dominated by just two arms wrapping off the ends of a central bar of stars.
Public Domain | Image courtesy of NASA.

Consider this…

“A Descent into the Maelstrom”

I became possessed with the keenest curiosity about the whirl itself. I positively felt a wish to explore its depths, even at the sacrifice I was going to make; and my principal grief was that I should never be able to tell my old companion on the shore about the mysteries I should see.

—Edgar Allan Poe 1841

License

Icon for the Creative Commons Attribution 4.0 International License

Introduction to Astronomy Copyright © by Lumen Learning is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

Share This Book