El Gordo is biggest distant galaxy cluster found yet — and it’s still growing

May 13, 2017

By Jessica Phelan

This galaxy cluster, which has been nicknamed “El Gordo” for the “big” or “fat” one in Spanish, is a remarkable object. Found in the distant Universe by Chandra and the Atacama Cosmology Telescope, El Gordo appears to be the most massive, the hottest, and gives off the most X-rays of any known cluster at its distance or beyond.
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

El Gordo, the largest distant cluster of galaxies yet to be identified, has been spotted by astronomers in Chile.

It was discovered using NASA's Chandra X-ray Observatory in space and the Atacama Cosmology Telescope in Chile.

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Announcing the discovery at the 219th American Astronomical Society meeting in Austin, Texas, yesterday, US and Chilean researchers said the cluster lay more than 7 billion light-years away from Earth and has mass about 2 million billion times that of our Sun.

Its official name is ACT-CL J0102-4915, but it has been nicknamed El Gordo—Spanish for "the fat one"—because of its monster size, study co-author John P. Hughes of Rutgers University told Space.com.

And it's still growing: extremely hot gas, plus what appear to be two distinct, comet-like "tails," have led scientists to conclude that El Gordo is, in fact, the site of two galaxy clusters colliding with each other at several million miles per hour.

"We could extrapolate what its mass will be; unfortunately the models are uncertain, but it could become the most massive cluster known about, even when we count the nearby universe," Hughes told the BBC.

Because El Gordo is so far away from Earth, we are seeing it as it was more than 7 billion years ago, when the universe was only half its current age, Hughes explained.

Reseachers hope that studying its properties will lead to new clues about the formation of the universe and the unseen dark matter and dark energy believed to make it up.