Astronomers find humongous galaxy cluster, thanks to gravitational lensing

Using NASA's Huble Space Telescope, astronomers have detected a huge cluster of galaxies some?10 billion light-years away. The cluster is so massive that it?distorts light that passes near it.?

By SPACE.com Staff,?SPACE.com / June 26, 2012

A diagram (not to scale) of how gravitational lensing works.

NASA, ESA & L. Cal?ada

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The most massive faraway cluster of galaxies has been found, thanks to a fortuitous astrophysical alignment that helped astronomers detect the mammoth grouping.

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The galaxy cluster, named IDCS J1426.5+3508, is located a staggering 10 billion light-years away from Earth, and researchers spotted the behemoth because its gravitational field is so strong that it is warping the light coming from a galaxy behind it. Galaxy clusters are the most massive structures in our universe, and are made up of hundreds to thousands of galaxies that are bound together by gravity.

"When I first saw it, I kept staring at it, thinking it would go away," study lead author Anthony Gonzalez, an astronomer at the University of Florida in Gainesville, said in a statement. "The galaxy behind the cluster is a typical run-of-the-mill galaxy with a lot of young stars, but the galaxy cluster in front of it is a whopper for that range. However, it's really the way that the two systems are lined up that makes the occurrence truly remarkable."

This fluke alignment created what's called a gravitational lens, which occurs when a massive object, such as a black hole or galaxy cluster, lies directly between an observer (or telescope), and a more distant target in the background.

The powerful gravitational force of the object in the foreground warps the light being emitted by the more distant target, bending and twisting it on its path to the telescope.

Gravitational lensing from the faraway galaxy has never been observed behind a cluster at such an enormous distance, the researchers said.

Since this galaxy cluster is so distant ? 10 billion light-years away ? it existed when the universe was only one-quarter of its present age. The universe is estimated to be roughly 13.7 billion years old. Current theories for how the universe evolved suggest that relatively few of these galaxy clusters were present when the universe was in its infancy, the researchers said. [The Universe: Big Bang to Now in 10 Easy Steps]

Still, finding this galaxy cluster represents a serendipitous astrophysical discovery in itself, since the astronomers were scanning only a small 9-square degree section of the sky. For comparison, if you extend your arm in front of you and hold up your index finger, you will be covering approximately 1 square degree of the sky with your finger, Gonzalez explained.

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