This composite image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520, formed from a violent collision of massive galaxy clusters.
The natural-color image of the galaxies was taken with NASA's Hubble Space Telescope and with the Canada-France-Hawaii Telescope in Hawaii. Superimposed on the image are "false-colored" maps showing the concentration of starlight, hot gas, and dark matter. Starlight from galaxies, derived from observations by the Canada-France-Hawaii Telescope, is colored orange. The green-tinted regions show hot gas, as detected by NASA's Chandra X-ray Observatory. The gas is evidence that a collision took place. The blue-colored areas pinpoint the location of most of the mass in the cluster, which is dominated by dark matter. Dark matter is an invisible substance that makes up most of the universe's mass. The dark-matter map was derived from the Hubble Wide Field Planetary Camera 2 observations by detecting how light from distant objects is distorted by the cluster of galaxies, an effect called gravitational lensing.
The blend of blue and green in the center of the image reveals that a clump of dark matter resides near most of the hot gas, where very few galaxies are found. This finding confirms previous observations of a dark-matter core in the cluster. The result could present a challenge to basic theories of dark matter, which predict that galaxies should be anchored to dark matter, even during the shock of a collision.
Abell 520 resides 2.4 billion light-years away.
Credits
NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University, California)| About The Object | |
|---|---|
| Object Name | Abell 520 |
| Object Description | Merging Galaxy Cluster |
| R.A. Position | 04h 54m 18.98s |
| Dec. Position | 02° 56' 48.8" |
| Constellation | Orion |
| Distance | 2.4 billion light-years (740 million parsecs) |
| About The Data | |
| Data Description | The image was created from Hubble data from proposal : J. Dalcanton (University of Washington, Seattle), A. Mahdavi (San Francisco State University), H. Hoekstra (Leiden Observatory), and A. Babul (University of Victoria, BC). The science paper is led by M.J. Jee (University of California, Davis). |
| Instrument | HST>WFPC2, CFHT, and Chandra |
| Exposure Dates | August 19-22, 2008, Exposure Time: 11 hours |
| Filters | CFHT (B), CFHT (V), HST/WFPC2 F814W (I), and CXO X-ray |
| About The Image | |
| Color Info | This image is a composite of separate exposures acquired by the HST/WFPC2 instrument, the Canada-France-Hawaii Telescope (CFHT), and the Chandra X-ray Observatory. Several filters were used to sample various wavelength and energy 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: White (visible): CFHT (B) + CFHT (V) + HST/WFPC2 F814W (I) Red (luminosity): CFHT Blue: HST/WFPC2 F814W (I) Green: CXO X-ray |
| Compass Image |  |
| About The Object | |
|---|---|
| Object Name | A name or catalog number that astronomers use to identify an astronomical object. |
| Object Description | The type of astronomical object. |
| R.A. Position | Right ascension – analogous to longitude – is one component of an object's position. |
| Dec. Position | Declination – analogous to latitude – is one component of an object's position. |
| Constellation | One of 88 recognized regions of the celestial sphere in which the object appears. |
| Distance | The 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. |
| Dimensions | The physical size of the object or the apparent angle it subtends on the sky. |
| About The Data | |
| Data Description |
|
| Instrument | The science instrument used to produce the data. |
| Exposure Dates | The date(s) that the telescope made its observations and the total exposure time. |
| Filters | The camera filters that were used in the science observations. |
| About The Image | |
| Image Credit | The primary individuals and institutions responsible for the content. |
| Publication Date | The date and time the release content became public. |
| Color Info | A brief description of the methods used to convert telescope data into the color image being presented. |
| Orientation | The rotation of the image on the sky with respect to the north pole of the celestial sphere. |
