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Stars gone wild

C. Wilson / McMaster U. / NASA / ESA
The galaxy Arp 220 is actually the result of a collision between two separate galaxies. The blue points in this Hubble image represent massive star clusters.

Galactic smash-ups are always good places to look for brilliant bursts of starbirth, and the Hubble Space Telescope has found a real doozy: a mashed-up merger of two galaxies, containing more than 200 mammoth star clusters. Astronomers say the biggest of those clusters contains enough material to make 10 million suns - which makes it twice as massive as any comparable star cluster in the Milky Way.

In today's image advisory, the Space Telescope Science Institute says the galaxy Arp 220, which is 250 million light-years from Earth in the constellation Serpens, is giving scientists a good idea of what the earliest galaxies in the universe could have looked like.

"This is starbirth in the extreme," astronomer Christine Wilson of McMaster University, the leader of the Arp 220 research team, was quoted as saying. "Our result implies that very high star-formation rates are required to form supermassive star clusters. This is a nearby look at a phenomenon that was common in the early universe, when many galaxies were merging."

The two galaxies that merged to form Arp 220 began running into each other about 700 million years ago. Based on an analysis of 14 clusters, Wilson's team says there has been at least two waves of starbirth: one long blast that has produced stars between 500 million and 70 million years ago, and another baby boom 10 million years ago.

Of course, all this is based on a timeline that ends with our current view of the galaxy. If we could magically suspend the special theory of relativity and see the galaxy up-close as it is "today," we would have a very different view of things. In fact, based on the current view, scientists say Arp 220 has enough gas to keep manufacturing star clusters for another 40 million years. Thus, if we could instantaneously travel through a wormhole into the galaxy itself, we would see that the fireworks have settled down by now.

Wilson and her team based their findings on observations made in 2002 by Hubble's Advanced Camera for Surveys, as well as earlier data from the Near Infrared Camera and Multi-Object Spectrometer. Their study was published in the April 20 issue of the Astrophysical Journal.

This view shows Arp 220 in visible light, but astronomers say the galaxy shines brightest in infrared light. In fact, Arp 220 is a classic ultra-luminous infrared galaxy, or ULIRG. Within such galaxies, new stars turn up the heat on the dust that surrounds them, causing the galaxies to glow brilliantly in the infrared spectrum.

Check out this story from earlier in the week for more about those intriguing ULIRGs - and if you're hankering for more galactic gems, click on over to our gallery of greatest hits from space.