It’s a pity we won’t be around when the Milky Way crashes into the Andromeda Galaxy five billion years from now. But if we were to catch the action, here’s what the smashup might look like. The simulation of the two colliding galaxies was created by Patrik Jonsson, Greg Novak and Joel Primack from the University of California, Santa Cruz. It got a semifinalist award at the 2008 NSF Science & Engineering Visualization Challenge.
Each spiral will sweep around the other, dragging out clouds of gases and dust to form prominent tidal tails. Reaching out to one another a second time, they’d trigger the formation of an intergalactic bridge. During each pass, colliding gases would spawn new stars. In the end, the combatants would collide outright, losing their separate identities and birthing a new galactic system.How do we know all this? By imaging other galactic pairs that are, right now in deep space, slamming into one another and creating messy crash scenes. These images are being taken with NASA’s Spitzer Space Telescope and Galaxy Evolution Explorer. GALEX’s ultraviolet views reveal concentrations of hot young stars, while Spitzer’s infrared images show clouds of warm dust in the galaxies.
Now researchers led by Lauranne Lanz (Harvard Smithsonian Center for Astrophysics) have combined the data from these telescopes to produce an atlas of galactic “train wrecks” — 50 colliding systems involving 111 galaxies.Each of these collisions takes at least a few million years to play out, making it impossible for humans to ever witness a galactic-scale smashup from start to finish. But every image in the Spitzer-GALEX compilation portrays a different phase of the collision, making it possible to get a good sense of how these gargantuan encounters might play out.
“The atlas is the first step in reading the story of how galaxies form, grow, and evolve,” said Lanz, who presented her findings at last week’s American Astronomical Society conference in Boston. Her team’s images will be used to generate computer simulations of these collisions. That’s something worth waiting for.