Abell 901/902
Credit: ESO
This deep-field image shows what is known as a supercluster of
galaxies — a giant group of galaxy clusters which are themselves
clustered together. This one, known as Abell 901/902, comprises three
separate main clusters and a number of filaments of galaxies, typical of
such super-structures. One cluster, Abell 901a, can be seen above and
just to the right of the prominent red foreground star near the middle
of the image. Another, Abell 901b, is further to the right of Abell
901a, and slightly lower. Finally, the cluster Abell 902 is directly
below the red star, towards the bottom of the image.
The Abell 901/902 supercluster is located a little over two billion
light-years from Earth, and contains hundreds of galaxies in a region
about 16 million light-years across. For comparison, the Local Group of
galaxies — which contains our Milky Way among more than 50 others —
measures roughly ten million light-years across.
This image was taken by the Wide Field Imager (WFI) camera on the MPG/ESO 2.2-metre telescope, located at the La Silla Observatory in Chile. Using data from the WFI and from the NASA/ESA Hubble Space Telescope, in 2008 astronomers were able to precisely map the distribution of dark matter in the supercluster,
showing that the clusters and individual galaxies which comprise the
super-structure reside within vast clumps of dark matter. To do this,
astronomers looked at how the light from 60 000 faraway galaxies located
behind the supercluster was being distorted by the gravitational
influence of the dark matter it contains, thus revealing its
distribution. The mass of the four main dark matter clumps of Abell
901/902 is thought to be around ten trillion times that of the Sun.
The observations shown here are part of the COMBO-17 survey, a survey
of the sky undertaken in 17 different optical filters using the WFI
camera. The COMBO-17 project has so far found over 25 000 galaxies.
Links
- The COMBO-17 survey at the Max-Planck-Institut für Astronomie, Heidelberg
- A wider-field view of the area around the Abell 901/902 supercluster
Source: ESO
