A MEETING WITH THE UNIVERSE

Chapter 4



X-ray type photo of a supernova remnant

BEYOND THE SOLAR SYSTEM

David Gilman

Blast from an unseen explosion.
Here, photographed in X-rays by the HEAO-2 satellite, supernova remnant Cassiopeia A is the expanding blast from a star that exploded in the late seventeenth century. Historical records suggest that astronomers of the time missed the event, although one observer may have seen a faint star at the location of the explosion. Cassiopeia A is one of the most conspicuous objects found with X-ray telescopes, although only very dim nondescript wisps ofgas are seen on visible-light photographs.



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