NASA Hubble Team Finds Monster “El Gordo” Galaxy Cluster Bigger Than Thought
Image Credit: NASA, ESA, and J. Jee (University of California, Davis)
NASA’s Hubble Space Telescope has weighed the largest known galaxy cluster in the distant universe, catalogued as ACT-CL J0102-4915, and found it definitely lives up to its nickname — El Gordo (Spanish for “the fat one”).
By measuring how much the cluster’s gravity warps images of galaxies in the distant background, a team of astronomers has calculated the cluster’s mass to be as much as 3 million billion times the mass of our sun. Hubble data show the galaxy cluster, which is 9.7 billion light-years away from Earth, is roughly 43 percent more massive than earlier estimates.
The team used Hubble to measure how strongly the mass of the cluster warped space. Hubble’s high resolution allowed measurements of so-called “weak lensing,” where the cluster’s immense gravity subtly distorts space like a funhouse mirror and warps images of background galaxies. The greater the warping, the more mass is locked up in the cluster.
“What I did is basically look at the shapes of the background galaxies that are farther away than the cluster itself,” explained lead author James Jee of the University of California at Davis. “It’s given us an even stronger probability that this is really an amazing system very early in the universe.”
A fraction of this mass is locked up in several hundred galaxies that inhabit the cluster and a larger fraction is in hot gas that fills the entire volume of the cluster. The rest is tied up in dark matter, an invisible form of matter that makes up the bulk of the mass of the universe.
