for National Geographic News
Four galaxies are crashing into each other in one of the largest collisions ever seen, scientists say.
The galactic crash was spotted by astronomers using NASA's Spitzer Space Telescope, which detected a fan-shaped plume coming from a cluster of galaxies nearly five billion light-years away.
When fully merged, the new galaxy will be up to ten times as large as the Milky Way, astronomers said.
"Most galaxy mergers are like small pickup trucks filled with sand colliding," explained Kenneth Rines, an astronomer at the Harvard-Smithsonian Center for Astrophysics.
"This big merger is like two big rigs full of sand colliding and flinging sand everywhere. In this case, the sand represents stars."
Common Occurrence Made Unique
Galactic mergers are fairly common, Rines explained. (Read related story: "Earth Likely to Relocate in Galactic Collision" [May 16, 2007].)
Most cosmic crashes involve two galaxies of similar size or smaller galaxies coalescing into a larger one.
What makes this event unique is the sheer size and number of galaxies involved, Rines said.
"This is a very unusual case," Rines said. "It's a first to have four galaxies merging."
Three of the star systems are about the size of the Milky Way, and the fourth is about three times as large.
(Download a wallpaper photo of the Milky Way.)
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