Giant Galaxy Cluster, Blue Stars and Cosmic Explosions

BY Jenny Marder  January 12, 2012 at 5:15 PM EST

Scientists have found the biggest distant galaxy cluster ever seen, using NASA’s Chandra X-ray Observatory and the Atacama Cosmology Telescope in Chile. Image: X-ray: NASA/CXC/Rutgers/J.Hughes et al, Optical: ESO/VLT/Pontificia Universidad. Catolica de Chile/L.Infante & SOAR (MSU/NOAO/UNC/CNPq-Brazil)/Rutgers/F.Menanteau, IR: NASA/JPL/Rutgers/F.Menanteau.

In the far-flung distant universe, 7 billion light years away, a super galaxy cluster has been discovered by an international team of scientists. It’s so astonishingly enormous that it’s been dubbed El Gordo — Spanish for “the fat one.”

It is the most massive, hottest, brightest galaxy cluster ever seen. Its age is half that of the universe now, and much of its mass is made up of dark matter. And scientists have glimpsed it in the midst of a violent merger, with two separate clusters colliding at several million miles per hour, wrenching normal matter apart from the dark matter in the process.

The finding was released in the Astrophysical Journal and presented at the American Astronomical Society meeting this week. For more findings from the conference, view our slide show:

To put it in perspective, the clusters are roughly the size of 20,000 Milky Ways and two quadrillion times the mass of our sun. Scientists believe that inside the cluster are thousands of galaxies like ours, each with millions of stars, some of which may have planets that resemble our own, according to Felipe Menanteau, an astrophysicist at Rutgers and the study’s first author.

“The message I want you to take away is that we’ve discovered an exceptional galaxy cluster,” said study author Jack Hughes of Rutgers University, at a recent press conference.

The space between the galaxies in the clusters is full of hot gas, highly compressed due to gravity. That gas is made up of normal matter — protons, electrons and neutrons — the stuff that makes up the Earth and the sun and us.

“The Gordo cluster looks a little bit like a comet, because you can see how the gas is being streaked out from one of the components,” Menanteau said.

But most of the mass in the cluster is made of dark matter, an exotic matter that scientists are still trying to understand. Dark matter is collision-less, Hughes said. “It streams through each other — expands out, whereas gas interacts with other gas particles.”

Rich galaxy clusters such as this help to verify our understanding of the early universe and the nature of dark matter, said Larry David of Harvard University’s High Energy Astrophysics Division.

“Such objects — their formation and growth — are very sensitive probes for understanding the underlying cosmology of the universe and the basic constituents of the universe,” David said.

Scientists discovered the cluster using the Atacama Cosmology Telescope, located in a dry, high plain in Northern Chile. NASA’s Chandra telescope contributed data on the temperature and structure of the hot gas contained in the cluster.