Galaxies in Collision

Here’s a depressing thought: before this solar system of ours ceases to be, the Milky Way in which we ride will collide with the Andromeda Galaxy, currently only 2.5 million light years away and closing fast.  And to make matters worse, our Sun, by then a very old star on its way to becoming a red giant and then dying out as a white dwarf, will be consigned to the edges of the newly meshed double galaxy. That’s the upshot of a paper from the Harvard-Smithsonian Center for Astrophysics, where T.J. Cox and Avi Loeb have done the math.  They predict that when the two galaxies have merged, the sun will be 100,000 light years from the center.  Today we’re about 25,000 light years from the center of the Milky Way–which gives science fiction writers plenty of ammo to write about how we’re a minor star off to one side of an unimportant galaxy. The good news is that this will only happen 5 billion years from now–by which time the Sun will have brightened and heated enough to boil away the Earth’s oceans. Cox and Loeb have sent their paper to Monthly Notices of the Royal Astronomical Society.  Loeb is quoted as joking, "This is the first paper in my publication record that has a chance of being cited five billion years from now." I know folks at the Center for Astrophysics.  They’re really very nice, upbeat people.
(Above: Composite image of Andromeda galaxy, from NASA’s Galaxy Evolution Explorer and the Spitzer Space Telescope.)