| ACT-CL J0102-4915 | |
|---|---|
 El Gordo consists of two separate galaxy subclusters colliding at several million kilometres per hour. | |
| Observation data (EpochJ2000.0[1]) | |
| Constellation(s) | Phoenix |
| Right ascension | 01h 02m 52.50s[1] |
| Declination | −49° 14′ 58.0″[1] |
| Redshift | 0.87[1] |
| Other designations | |
| El Gordo,[1]ACT-CL J0102-4915,[2]SPT-CL J0102-4915[2] | |
El Gordo (lit.The Fat One) (ACT-CL J0102-4915 orSPT-CL J0102-4915) is the largest distantgalaxy cluster observed at its distance or beyond, as of 2011. As of 2014, it held the record for being the largest distant galaxy cluster to have been discovered with a mass of slightly less than three quadrillionsolar masses[3][4][5][6] although later its mass was reduced to about2.1×1015 (2.1 quadrillion) solar masses with a 10% uncertainty.[7] It was found byNASA'sChandra X-ray Observatory, theAtacama Cosmology Telescope (funded by theNational Science Foundation) and theEuropean Southern Observatory'sVery Large Telescope.[8]
This galaxy cluster, officially named as, 'ACT-CL J0102-4915', has been given a 'nickname' by the researchers as 'El Gordo', which stands for "the Fat One" or "the Big One" inSpanish. It is located more than 7 billionlight-years fromEarth.[9]
Findings and results on 'El Gordo' were announced at the 219th meeting ofAmerican Astronomical Society in Austin, Texas.[10]
Findings from the European Southern Observatory'sVery Large Telescope and theChandra X-ray Observatory show that El Gordo is composed of two separategalaxy subclusters, colliding at several million kilometers per hour.[11] These observations (using X-ray data and other characteristics) suggest that El Gordo most probably formed in the same manner as theBullet Cluster (which is located 4 billion light-years fromEarth).[12][13][14][15]
It was claimed that this interacting cluster presents problems for the conventionalLambda-CDM model of cosmology because it is hard to reconcile ΛCDM's model of galaxy formation with the combination of how early El Gordo is observed in cosmic history, its large mass, and its high collision velocity.[16] It was argued that later more accurate measurements have rejected this claim and led to a smaller mass estimate fully consistent with the ΛCDM cosmology.[7] However, the claims of consistency with ΛCDM were shown to be due to the assumption of a very low collision velocity that is not supported by any hydrodynamical simulations, not because of the slightly reduced mass estimate, which by itself does not solve the problem.[17]
![Galaxy cluster ACT-CL J0102-4915 contains the mass of about two million billion suns.[18]](/mt/?noimg=&dark=on&url=https%3a%2f%2fwikipedia.org%2fwiki%2fFile%3aA_gargantuan_collision_ACT-CL_J0102-4915.jpg)
![Hubble image of ACT-CL J0102-4915[19]](/mt/?noimg=&dark=on&url=https%3a%2f%2fwikipedia.org%2fwiki%2fFile%3aGalaxy_Cluster_%2527El_Gordo%2527_with_Mass_Map.jpg)
_(elgordo1).jpg)
