Creation of One of the Largest Galaxies in the Universe — Six Times Size of the Milky Way

In a galactic replay of merging of the Earth's tectonic plates into a massive supercontinent known as Pangea 250 million years ago, the Spitzer Space Telescope caught images of four massive galaxies slamming into each other and kicking up billions of stars like grains of sand! As the largest galactic pileup in the known universe, it will produce a huge offspring.

The massive collision will eventually cause the four galaxies to become a single behemoth galaxy that will be about 10 times bigger than our Milky Way. From a scientific perspective, this rare sighting provide and unprecedented look at how the most massive galaxies form.

The new quadruple merger was discovered serendipitously during a Spitzer survey of a distant cluster of galaxies, called CL0958+4702, located nearly five billion light-years away. The infrared telescope first spotted an unusually large fan-shaped plume of light coming out of a gathering of four blob-shaped, or elliptical, galaxies. Three of the galaxies are about the size of the Milky Way, while the fourth is three times as big.

"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."

Some of the stars tossed outward in the monstrous merger will orbit in isolated areas outside the borders of any of the galaxies. Such abandoned stars would have planets with night-time views strikingly different from our own. Rather than seeing many individual stars, there would be more visible galaxies adorning the night sky.

Collisions between galaxies are believed to be a major force in shaping our universe. Our own galaxy cannibalizes on smaller galaxies that come to close and are sucked in, as it has for millions of years. Though stars in merging galaxies are tossed around like grains of sand, the shear quantity of space between objects ultimately allows the galaxies to survive the ride. Our Milky Way galaxy is due to collide with a much bigger “sister” spiral galaxy, Andromeda, in about five billion years.

While mergers between pairs of galaxies that are similar, or one big galaxy and several smaller ones, has already been documented—no major mergers between multiple hefty “big rig” galaxies have ever been seen until now. Three of the galaxies are the size of the Milky Way, while the fourth is three times as big. Rines says the size of the completely merged galaxy will be impressive indeed.

"When this merger is complete, this will be one of the biggest galaxies in the universe."

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