Abell 2151 Galaxy Cluster

Copyright  Mark Hanson

Description by Sakib Rasool

Abell 2151 is a mighty cluster of galaxies with a surplus of beautiful interacting galaxies. Interestingly its distribution is quite chaotic and lacks the typical central elliptical galaxy that is a common feature of most galaxy clusters. However the brightest galaxy is the elliptical NGC 6041.

In the grand scheme of the universe, Abell 2151 (also known as the Hercules Galaxy Cluster) is located 500 million light years away and covers an area of 6 million light years with about 200 galaxies. It is part of the Hercules Supercluster, which is part of an even larger extragalactic structure simply known as the Great Wall. This has a huge span of 500 million light years and was discovered in the 1980's by Margaret Geller and John Huchra.

One aspect of Abell 2151 that is immediately apparent is the abundance of peculiar and interacting galaxies. In fact, there are so many that a record number of four were included in the Arp Atlas, the most for any galaxy cluster. These include Arp 71 (NGC 6045), Arp 122 (NGC 6040), Arp 172 (IC 1178/81) and Arp 272 (NGC 6050/IC 1179).

NGC 6040 is an interesting pair of galaxies interacting with each other and in the process of being absorbed into the galaxy cluster, its neutral hydrogen gas has been removed through ram pressure stripping, a phenomenon that has been observed in other galaxy clusters. NGC 6050 and IC 1179 represent a titanic collision between two behemoths that have been observed with the Hubble Space Telescope, which appears to show a third member in this system.

Arguably the most distinguished member of Abell 2151 is IC 1182, a strange chaotic wreck of a galaxy that was somehow overlooked by Halton Arp. Although it is tempting to perceive the elongated blue structure as a jet launched from its core, it is in fact a tidal tail with a weaker second one near the opposing side. Another famous example of tidal tails being misconstrued as jets are the ones associated with the southern galaxy NGC 1097. In IC 1182, the longer tidal tail has a length of 205,000 light years while the smaller one is 88,000 light years long. It is very llkely its unique morphology is the result of an ongoing merger between two galaxies. Another interesting conclusion drawn from professional studies is that some of the blue knots in the large tidal tail might be in the process of forming tidal dwarf galaxies!

"Stellar Winds Observatory" a/k/a Stan Watson Observatory at Dark Sky New Mexico

 Planewave 17" LRGB 500,280,280,280