NASA’S Spitzer Spies Monster Galaxy Pileup
Four galaxies are slamming into each other and kicking up billions of stars in one of the largest cosmic smash-ups ever observed.

The clashing galaxies, spotted by NASA’s Spitzer Space Telescope, will eventually merge into a single, behemoth galaxy up to 10 times as massive as our own Milky Way. This rare sighting provides an unprecedented look at how the most massive galaxies in the universe form.

“Most of the galaxy mergers we already knew about are like compact cars crashing together,” said Kenneth Rines of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. “What we have here is like four sand trucks smashing together, flinging sand everywhere.” Rines is lead author of a new paper accepted for publication in Astrophysical Journal Letters.

Collisions, or mergers, between galaxies are common in the universe. Gravity causes some galaxies that are close together to tangle and ultimately unite over a period of millions of years. Though stars in merging galaxies are tossed around like sand, they have a lot of space between them and survive the ride. Our Milky Way galaxy will team up with the Andromeda galaxy in five billion years.