The giant galaxy cluster Abell 2744, nicknamed Pandora's Cluster, appears to be the result of a simultaneous pile-up of at least four separate, smaller galaxy clusters. The crash took place over a span of 350 million years.
The galaxies in the cluster make up less than five percent of its mass. The gas (around 20 percent) is so hot that it shines only in X-rays (colored red in this image). The distribution of invisible dark matter (making up around 75 percent of the cluster's mass) is colored here in blue.
Dark matter does not emit, absorb, or reflect light, but it makes itself apparent through its gravitational attraction. To pinpoint the location of this elusive substance the team exploited a phenomenon known as gravitational lensing. This is the bending of light rays from distant galaxies as they pass through the gravitational field created by the cluster. The result is a series of telltale distortions in the images of galaxies in the background of the Hubble and VLT observations. By carefully analyzing the way that these images are distorted, it is possible to accurately map where the dark matter lies.
Chandra mapped the distribution of hot gas in the cluster.
The data suggest that the complex collision has separated out some of the hot gas (which interacts upon collision) and the dark matter (which does not) so that they now lie apart from each other, and from the visible galaxies. Near the core of the cluster there is a "bullet" shape where the gas of one cluster collided with that of another to create a shock wave. The dark matter passed through the collision unaffected.
In another part of the cluster, galaxies and dark matter can be found, but no hot gas. The gas may have been stripped away during the collision, leaving behind no more than a faint trail.
Credits
NASA, ESA, J. Merten (Institute for Theoretical Astrophysics, Heidelberg/Astronomical Observatory of Bologna), and D. Coe (STScI)| About The Object | |
|---|---|
| Object Name | Pandora's Cluster, Abell 2744 |
| Object Description | Galaxy Cluster with Gravitational Lensing |
| R.A. Position | 00h 14m 19.5s |
| Dec. Position | -30° 23' 19.18" |
| Constellation | Sculptor |
| Distance | Redshift: z=0.308 |
| About The Data | |
| Data Description | The image was created from Hubble data from proposal : R. Dupke (University of Michigan), N. Benitez (Astrophysical Institute of Andalucía, Spain), J. Krick (California Institute of Technology), B. Bregman (University of Michigan), D. Coe (STScI), L. Sodre (University of Sao Paulo), T. Broadhurst (Tel Aviv University, Wise Observatory), and R. Bernstein (University of California, Santa Cruz). The science team is led by J. Merten (Institute for Theoretical Astrophysics, Heidelberg/Astronomical Observatory of Bologna). |
| Instrument | HST>ACS/WFC, ESO>VLT, and CXO |
| Exposure Dates | October 27-30, 2009, Exposure Time: 12 hours |
| Filters | ACS/WFC: F438W (B), F606W (V), and F814W (I) VLT: B, R, I Chandra X-ray |
| About The Image | |
| Color Info | The image is a composite of separate exposures made by Hubble Space Telescope ACS detectors, the ESO's Very Large Telescope (VLT), and the Chandra ACIS detector. Hubble provides the central, most detailed part of the image, while the VLT, which has a wider field of view, provides the outer parts of the image. A map of the cluster's dark matter distribution has also been applied to the image. The color results from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are: Blue: Dark Matter Map + F438W (B) + VLT B Green: F606W (V) + VLT R Red: Chandra X-ray data + F814W(I) + VLT I |
| 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. |
