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Sunday, April 11, 2010

Seeing the backside of a supernova

Chandra X-ray Observatory image of the supernova remnant Cassiopeia A.The red, green, and blue regions in this image show where the intensity of low, medium, and high-energy X-rays, respectively, is greatest.

Credit: NASA/CXC/MIT/UMass Amherst/M.D.Stage et al.

When cosmologists study the skies, they can only do so from the vantage point of the solar system. But a new detection method developed by Armin Rest of Harvard University and his colleagues have allowed scientists to see the back side of cosmic events.

The team has been studying a supernova called Cassiopeia A. Most of the observable light from that event went straight toward the solar system 330 years ago. However, a small amount of light first bounced off some clouds of interstellar dust, and then rebounded towards us. In other words, the dust clouds acted like giant mirrors, reflecting the back or sides of the supernova back towards us.

The researchers have already discovered that the different sides of the supernova explosion were not symmetrical. Gas from the explosion is zooming away in one particular direction much faster than in any other way. Meanwhile, the neutron star that resulted from the collapse of the star’s core is careening away in the direction opposite this gaseous surge.

By combining this new light-echo data with X-ray data, the cosmologists have been able to construct a 3D computer model of the supernova. You can watch a simulation here.