Crash will determine solar system’s fate

Ready for a change of scene? The solar system already lies in the suburbs of the Milky Way, but the sun and its planets will be yanked even farther away—to the galactic equivalent of Siberia—about 5 billion years from now, according to computer simulations by Thomas J. Cox and Avi Loeb of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

That’s when the Milky Way and its sister galaxy, Andromeda, long known to be on a collision course, will finally merge, the calculations indicate. The collision will happen before the sun becomes a burned-out cinder, Cox and Loeb say.

The pair’s simulations, recently posted online (, indicate that Andromeda and our galaxy will have their first close encounter about 2 billion years from now and will then swing around each other several times before combining to form a single, football-shaped galaxy. Our solar system will probably reside 100,000 light-years from the new galaxy’s center, about four times farther than its current distance from the Milky Way’s core.

“To my knowledge, nobody [had] specifically studied where the sun might end up” after the galaxies merge, comments theorist Greg Laughlin of the University of California, Santa Cruz.

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