XMM'S New Cluster
Credit: ESA/XMM-Newton Team

A Hidden Cluster Revealed

Clusters of galaxies are among the largest gravitationally bound entities in the Universe. In general it is difficult to hide something so large; however, near the plane of our own Milky Way Galaxy, thick clouds of gas and dust obscure our view of the rest of the Universe. Galaxy clusters are strong sources of X-rays (among the strongest known, in fact), and because X-rays can penetrate through the intervening "junk" in the plane of the Milky Way, astronomers hope that X-ray images of the plane of the Milky Way may reveal heretofore hidden objects in the distant Universe. On June 5, 2000, during a calibration observation of the plane of the Milky Way, the XMM-Newton X-ray observatory detected one such hidden object, a previously unknown cluster of galaxies. The image above shows the discovery, made by the XMM-Newton's EPIC camera; the unknown cluster of galaxies is visible as the extended red-colored source in the right middle of the false-color image. XMM-Newton was also able to measure the speed of the cluster, and showed that the cluster is receding from us due to the expansion of the universe. Using Hubble's Law the distance to the cluster is about 1 billion light years, so that XMM-Newton is observing the cluster as it was 1 billion years ago. Further studies by XMM-Newton (and other X-ray telescopes) of this cluster and others like it allow astronomers to understand how the Universe is structured, and how chemical elements are produced and distributed.

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Page Author: Dr. Michael F. Corcoran
Last modified June 28, 2000