Astronomer Explains Consequences of a More Massive Milky Way

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The Milky Way galaxy, Earth's ride through space, is more mini-van than mini-Cooper, report scientists at the American Astronomical Society meeting this week. New technology allowing them to make high-precision measurements showed that not only is the Milky Way moving 100,000 miles per hour faster than previously thought, it is also 50 percent larger.

To make sense of the news, I spoke with Mark Reid, an astronomer at the Harvard-Smithsonian Center for Astrophysics who contributed to this research.

Q: What does the new calculation of a faster spinning galaxy mean for us?

A: Nothing. We wouldn't notice the difference at all. If we lived billions of years, then we would certainly see that all the constellations and the patterns in the Milky Way would change a little faster but we're not going to notice that.

Q: How does it impact us then?

The Milky Way galaxy now has the same rotation speed with the Andromeda Galaxy, our neighbor. That means it's as massive as the Andromeda Galaxy and there's a lot of ramifications for the evolution of the galaxies around us. For example, the Milky Way and Andromeda are the two biggest galaxies in what we call the Local Group, this little neck of the woods of the universe. There's a good chance that these two galaxies will hit each other in about five billion years or so. Now, by realizing that there's more mass in the Milky Way than we thought, makes this more likely and that it will happen a bit sooner because there's more gravity pulling them together.

Q: What happens when two galaxies collide?

A: If you're sitting here on the Earth, you would never know it because there's so much empty space between all the stars. If we have two populations of stars merging through each other, they won't collide or things like that. But what will happen is the Milky Way and the other galaxy Andromeda will change dramatically. They might merge into one galaxy for example. So over very long time periods the entire sky would change. In fact, it's possible that the sun and Earth could get ejected out of the galaxy in such a collision. That's a distinct possibility. It wouldn't affect life here, but it would certainly affect what we see when we look out into the universe.

For more on this story, see reporting done by The New York Times, Wired, and Discover.

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