‘El Gordo’ Largest Galaxy Cluster Bigger Than Previously Thought: NASA

A distant massive galaxy cluster 'El Gordo' ( the fat one ) lives up to its nick name as new calculations reveal that the cluster is three million billion times the mass of our Sun.

The ancient 'El Gordo' galaxy cluster officially called ACT-CL J0102-415 is known to be the hottest and biggest cluster of galaxies ever identified in the early universe.  Located some 9.7 billion light years away from Earth, El Gordo (the fat one in Spanish) is a cosmological rarity. Astronomers at the space agency using Hubble Space Telescope reweighed this massive body and come up with a new calculation.

New calculations reveal that the the El Gordo galaxy cluster is much bigger than what the astronomers had earlier estimated. The cluster's mass is a whopping 3 million billion times the mass of our Sun, i.e. the cluster is approximately 43 percent more massive than what previous calculations showed, which were made using X-ray and dynamic studies.

"We were in dire need for an independent and more robust mass estimate given how extreme this cluster is and how rare its existence is in the current cosmological model. There was all this kinematic energy that could be unaccounted for and could potentially suggests that we were actually underestimating the mass," Felipe Menanteau of the University of Illinois at Urbana-Champaign, said in a statement.

A fraction of El Gordo's mass is trapped in several hundred galaxies that inhabit the cluster and a much larger fraction of the mass is in the hot gas that fills the cluster. The remaining mass can be accounted as the invisible dark matter that makes the bulk of the mass of the universe.

Though other massive galaxy clusters have been identified such as the Bullet Cluster, no other cluster matches the size of the El Gordo. The immense size of El Grodo was initially reported in 2012.  The previous estimates were based on the motion of the galaxies within the cluster and the high temperatures of hot gas between the galaxies.

But the astronomers noticed that El Gordo appeared as if it was a result of a collision between a pair of galaxy clusters.  

"We wondered what happens when you catch a cluster in the midst of a major merger and how the merger process influences both the X-ray gas and the motion of the galaxies," explained John Hughes of Rutgers University. "So the bottom line is that because of the complicated merger state, it left some questions about the reliability of the mass estimates we were making."

It is then the astronomers turned to data gathered by Hubble. Using this data they measured the mass of the cluster. The team could also measure the weak lensing ( a gravitational lens that is formed by the gravities of galaxies, which  combine and form such a huge force that they warp the surrounding space).

James Jee, of the University of California at Davis, the principle investigator of the El Gordo study said, "What I did is basically look at the shapes of the background galaxies that are farther away than the cluster itself. It's given us an even stronger probability that this is really an amazing system very early in the universe."

The team now plans to get a large mosaic image of the cluster.  But the cluster is so massive that they are doubtful on whether it fits into Hubble field of view. This way they will view the giant from its side. In order to get a complete picture of El Gordo they have to have a larger field of view.