* Astronomy

Evidence for an awesome upheaval in a massive galaxy cluster was discovered in an image made by NASA's Chandra X-ray Observatory. The origin of a bright arc of ferociously hot gas extending over two million light years requires one of the most energetic events ever detected.
The cluster of galaxies is filled with tenuous gas at 170 million degree Celsius that is bound by the mass equivalent of a quadrillion, or 1,000 trillion, suns. The temperature and mass make this cluster a giant among giants.

"The huge feature detected in the cluster, combined with the high temperature, points to an exceptionally dramatic event in the nearby Universe.  While we're not sure what caused it, we've narrowed it down to a couple of exciting possibilities" - Ralph Kraft of the Harvard-Smithsonian Centre for Astrophysics (CfA) in Cambridge, Mass., and leader of a team of astronomers involved in this research.

The favoured explanation for the bright X-ray arc is that two massive galaxy clusters are undergoing a collision at about 4 million miles per hour. Shock waves generated by the violent encounter of the clusters' hot gas clouds could produce a sharp change in pressure along the boundary where the collision is occurring, giving rise to the observed arc-shaped structure which resembles a titanic weather front.

"Although this would be an extreme collision, one of the most powerful ever seen, we think this may be what is going on" - Martin Hardcastle, University of Hertfordshire, United Kingdom.

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