Space.com - 5/27/13
The merger is occurring 11 billion light-years away, meaning that astronomers are seeing the two colliding galaxies as they were about 3 billion years after the Big Bang that created the universe. During this epoch, "red and dead" elliptical galaxies full of old stars were common.
Fu and his colleagues initially thought the two merging galaxies were a singleton, dubbed HXMM01, when they saw it with the European Space Agency's infrared Herschel space telescope.
But follow-up observations with a variety of other instruments, both on the ground and in space, revealed that HXMM01 is actually two galaxies on a collision course, separated by about 62,000 light-years at the moment.
The gas-rich two-galaxy system contains the stellar equivalent of about 400 billion suns and is churning out new stars at a fantastic clip — about 2,000 per year, researchers said. For comparison, just two to three new stars are born every year in our own Milky Way.
At this rate, the newly forming elliptical galaxy will exhaust its gas reservoirs and cease birthing stars in just 200 million years, going red and dead in what researchers describe as a surprisingly short period of time.
"The common thought was that massive galaxies form by accreting smaller galaxies and the growth, though rapid, would last more than 200 million years," co-author Asantha Cooray, also of UC-Irvine, told SPACE.com via email.
"And the formation was expected to not be as efficient as we have observed," Cooray added. "The 40 percent efficiency
of star formation, the efficiency at which gas is converted to stars in one rotation of the system, was unexpected."
Link: Space.com
