Abell 2142, also called A2142 and located in the constellation Corona Borealis, is an X-ray luminous galaxy cluster. Its creation is due to the merger between two galaxy clusters. It is one of the largest objects in the universe and is six million light years across. It holds hundreds of galaxies and enough gas to make a thousand more.
The pressure fronts in the system have been traced in detail and are relatively cool 50 million degree Celsius. The central region is embedded in large elongated cloud of 70 million degree Celsius gas. All of that is within a “atmosphere” at a temperature of 100 million degree Celsius.
The Abell catalogue of rich clusters of galaxies, originally published by UCLA astronomer George Ogden Abell (1927-1983) in 1958, includes Abell 2142. At 1.2 billion light years away, Abell 2142 continues to move away from us with a heliocentric redshift of .0909. It has a visual magnitude of 16.0.
Previously, due to lack of technology, we were unable to get an accurate temperature map of subclusters; however, with Chandra and XMM-Newton (two current X-ray observatories) we are able to get a more accurate reading and therefore can tell more about the stage, geometry and velocity of the merger. This has cause a attention to be poured on A2142 due to its ability to shed light on the dynamics of mergers between galaxies.
The X-ray emissions from A2142 show are mostly smooth and symmetric, suggesting it is a result of a galaxy cluster merge 1-2 billion years after the initial core crossing. In the early stages of a merger one would expect uneven X-ray emissions and shock fronts. Markevitch et al. have proposed that the central galaxy (designated G1) of a more massive cluster has merged with the former central galaxy (G2) of the less massive cluster. The central area being relatively cool suggests that the heating caused by earlier shock fronts missed the central core, instead it interacted with the surrounding gas.