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When Did the Cas A Supernova Occur?

-- | April 4, 2015

Question: There is a statement at the following link to the image archive that I do not understand: http://images.nrao.edu/Galactic_Sources/Supernova_Remnants/569. The text states that this supernova is 10,000 light years away, but that the supernova event happened 300 years ago. If that were the case, then surely we would not see it for another 9,700 years. Is the text misleading, or am I misunderstanding something? Thank you. — Jeremy

Answer: I believe what the text should say is that it is believed that the first light from the supernova reached Earth about 300 years ago, not that the supernova event happened 300 years ago. As you point out, the supernova event must have happened more than 11,000 years ago in order for light to have reached us.

Jeff Mangum

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