Galaxy Clusters

Galaxy clusters are large accumulations of galaxies, which are moving in the common gravitational field. The biggest galaxy clusters contain up to 3000 galaxies (spiral, elliptical, dwarf galaxies). The nearest large galaxy cluster is the so-called Virgo Cluster in the constellation of Virgo. It is about 60 million light years distant, and it extends over some 15 million light years. Other examples are the Perseus Cluster (240 Mio. light years), the Coma Cluster (300 million light years distant) and the Heckules Cluster (500 million light years distant).

Central region of the Virgo Cluster with the two bright elliptical galaxies M 84 (NGC 4374) and M 86 (NGC 4406).
Maksutov-Newton, Canon 1100Da, 13.5 hours

In the centre of the Virgo Cluster in the constellation of Virgo one can see a multitude of galaxies, foremost the elliptical galaxies M 84 and M 86, as well as a number of spiral galaxies and smaller ellipticals, which are all moving in the strong gravitational field of the Virgo Cluster. Some galaxies are strongly perturbed during their close passages of others. This can be best seen in the galaxy NGC 4388 in the east, which has been disrupted to some extent by a nearby elliptical galaxy. There are some salient dark regions a little bit west of the centre of NGC 4388: what we see here are giant complexes of molecular clouds, which were formed by the tidal forces imposed by the neighbouring galaxy.

Central region of the Virgo Cluster with the giant Elliptical Galaxy NGC 4486 (M 87)
Maksutov-Newton, Canon 1100Da, 23.9 hours

Close to the centre of the Virgo Cluster a large number of smaller elliptical galaxies can be seen. There are hardly any spiral galaxies because they have been swallowed by the giant galaxy M 87 by gravitational merging. M 87 consists of about 2.5 thousand billion (!) stars. Its centre hosts the biggest known black hole, with a mass of ca. 6.5 billion solar masses. Jets of high-energy particles are ejected from its immediate surroundings. These emit synchrotron radiation producing spectacular structures at radio frequencies (see Galaxy Overlays).

Central region of the Virgo Cluster of Galaxies

Maksutov-Newton, Canon 1100Da, 11.5 hrs.

We see the so-called Markarian Chain with the prominent elliptical galaxies M 84 and M 86, and the central elliptical galaxy M 87.

Perseus Cluster of Galaxies
Maksutov-Newton, Canon 1100Da, 15.5 hours

The Perseus Cluster of Galaxies is about 240 Millionen ly distant and contains more than 1000 galaxies. It is not relaxed, i.e. its galaxy distribution is still far from being spherical (as is e.g. the case in globular clusters). This will take a few more billions of years. The image exhibits a multitude of more yellowish galaxies, mostly ellipticals, which have finished their evolution. They formed via gravitational merging of smaller galaxies to larger and larger ones. The galaxies are moving in the cluster with very high speeds (600 - 1000 km/s).

Same image with annotation, in which both, the astronomical coordinates (right ascension and declination) and the optical identifications of all detected galaxies are overlayed. The image contains a total of 23 galaxies from the NGC catalogue, 6 galaxies from the IC catalogue, and 193 galaxies from the PGC catalogue.

Coma Cluster of Galaxies
ED-Refractor, Canon 1100Da, 11.2 hours

The Coma Cluster (Abell 1656) with more than 1000 galaxies is about 300 million ly distant. Its diameter is about 20 million ly. It consists of the main cluster, with a subcluster falling in at a speed of about 2000 km/s from the south-west. The above image exhibits a multitude of elliptical galaxies with their characteristic yellowish colour. The colour arises beause they only contain old and cool stars. Their evolution via gravitational merging of many smaller galaxies is largely finished. The image contains a total of 60 galaxies from the NGC catalogue, 33 galaxies from the IC catalogue, and 827 galaxies from the PGC catalogue.

Hercules Cluster of Galaxies
Maksutov-Newton, Canon 1100Da, 13.7 hours

The Hercules Cluster (Abell 2151) with about 200 galaxies is about 500 million ly distant. Its diameter is about 8 million ly. Most of its galaxies are spirals, implying that its evolution by gravitational merging of galaxies has not proceeded very far yet. The image contains a total of 14 galaxies from the NGC catalogue, 20 galaxies from the IC catalogue, and 256 galaxies from the PGC catalogue.