We live in a nice neighborhood. Of the galaxy, that is. The sun is about halfway toward the outer edge of the Milky Way. But the sun may have migrated vast distances through the galaxy to wind up where we are today. That’s according to computer models published in the September 10th Astrophysical Journal Letters.

By about nine billion years ago, the material for the galactic disk had mostly come together, but the actual disk formation hadn’t started. Scientists simulated the formation and evolution of the galaxy from that point, using over 100,000 hours of time on a University of Texas supercomputer and a computer cluster at the University of Washington.

Turns out that while a star is orbiting around the center of the galaxy, a spiral arm can intercept the star and radically alter that orbit. Which would explain a long-standing problem—the stars in our region have a much more varied chemistry than would be expected. Stellar migrations could thus be responsible for making our neighborhood within the Milky Way a much more diverse and interesting place.

—Steve Mirsky 

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