Quad Galaxy Collision

One of the biggest galaxy collisions ever observed is taking place at the centre of this image from Spitzer.
The four white blobs in the middle are large galaxies that have begun to tangle and ultimately merge into a single gargantuan galaxy.


The whitish cloud around the colliding galaxies contains billions of stars tossed out during the messy encounter. Other galaxies and stars appear in yellow, orange and red hues. Blue shows hot gas that permeates this distant region of tightly packed galaxies.

NASA's Spitzer Space Telescope serendipitously spotted the quadruple merger during a routine survey of a distant galaxy cluster, called CL0958+4702, located nearly 5 billion light years away.

Spitzer's infrared eyes observed an unusually large fan-shaped plume of light emerging from a gathering of four elliptical galaxies. Three of the galaxies are about the size of the Milky Way, while the fourth is three times as large.
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The plume turned out to be billions of elderly stars ejected and abandoned during the clash. About half of the stars in the plume will later fall back into the galaxies.

Spitzer observations also show that, unlike most known mergers, the galaxies involved in the quadruple collision are bereft of gas, the source material that fuels star birth. As a result, astronomers predict relatively few new stars will be born in the new, combined galaxy.


Artist's concept showing what the night sky might look like from a hypothetical planet around a star tossed out of an ongoing four-way collision between big galaxies.

Credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA

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