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Galaxy Cluster ‘El Gordo’ with Mass Map

This is a Hubble Space Telescope image of the most massive cluster of galaxies ever seen to exist when the universe was just half of its current age of 13.8 billion years. The cluster, catalogued as ACT-CL J0102-4915, contains several hundred galaxies swarming around under the collective gravitational pull. The total mass of the cluster, as refined in new Hubble measurements, is estimated to weigh as much as 3 million billion stars like our Sun (about 3,000 times as massive as our own Milky Way galaxy) – though most of the mass is hidden away as dark matter. The location of the dark matter is mapped out in the blue overlay. Because dark matter doesn't emit any radiation, Hubble astronomers instead precisely measure how its gravity warps the images of far background galaxies like a funhouse mirror. This allowed them to come up with a mass estimate for the cluster. The cluster was nicknamed El Gordo (Spanish for "the fat one") in 2012 when X-ray observations and kinematic studies first suggested it was unusually massive for the time in the early universe when it existed. The Hubble data have confirmed that the cluster is undergoing a violent merger between two smaller clusters.

About the Object

R.A. Position
R.A. PositionRight ascension – analogous to longitude – is one component of an object's position.
01h 2m 52.99s
Dec. Position
Dec. PositionDeclination – analogous to latitude – is one component of an object's position.
-49° 15' 19.01"
Constellation
ConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.
Phoenix
Distance
DistanceThe physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.
9.7 billion light-years (3 billion parsecs)

About the Data

Data Description
Data DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.
The Hubble data are from proposal 12755: J. Hughes (Rutgers University), F. Menanteau (Rutgers University/University of Illinois, Urbana-Champaign), L. Infante and L.F. Barrientos (Ponticia Universidad Catolica de Chile), and R. Mandelbaum (Carnegie Mellon University), and archival data from proposal 12477: F. High (University of Chicago) et al.
Instrument
InstrumentThe science instrument used to produce the data.
HST>ACS/WFC
Exposure Dates
Exposure DatesThe date(s) that the telescope made its observations and the total exposure time.
September - October, 2012
Filters
FiltersThe camera filters that were used in the science observations.
F606W ((V), F625W (r), F775W (i), F814W (I), and F850LP (z)

Object Name
Object NameA name or catalog number that astronomers use to identify an astronomical object.
El Gordo, ACT-CL J0102-4915
Object Description
Object DescriptionThe type of astronomical object.
Galaxy Cluster
Release Date
April 3, 2014
Science Release
Hubble Finds That Monster ‘El Gordo’ Galaxy Cluster Is Bigger Than Thought
Read the release
Credit
NASA, ESA, and J. Jee (University of California, Davis)

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This composite image includes exposures acquired by the ACS instruments on the Hubble Space Telescope. Several filters were used to sample broad wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are: Blue: F625W (r) Green: F775W (i) Red: F850LP (z) Cyan: Derived Mass

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