Cassiopeia A: supernova remnant, shell type (optical view) 19/08/1999
Click to return to main Cassiopeia A page Cas A is the remnant of a star that exploded about 300 years ago. The X-ray image shows an expanding shell of hot gas produced by the explosion. This gaseous shell is about 10 light years in diameter, and has a temperature of about 50 million degrees.

X-ray view
Infrared view
Radio view

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Image Credit: MDM Observatory.  
Two shock waves are visible: a fast outer shock and a slower inner shock. The inner shock wave is believed to be due to the collision of the ejecta from the supernova explosion with a circumstellar shell of material, heating it to a temperature of ten million degrees. The outer shock wave is analogous to an awesome sonic boom resulting from this collision. The optical image of Cas A shows matter with a temperature of about ten thousand degrees. Some of these wisps contain high concentrations of heavy elements and are thought to be dense clumps of ejected stellar material.  
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