Prominent constellation of the northern hemisphere, named after the mother of Andromeda (who was the wife of Perseus). It has a distinctive W-shape, and contains one of the most powerful radio sources in the sky, Cassiopeia A. This is the remains of a
supernova (star explosion) that occurred
c. AD 1702, too far away to be seen from Earth.
It was in Cassiopeia that Danish astronomer Tycho
Brahe observed a new star in 1572, probably a supernova, since it was visible in daylight and outshone
Venus for ten days.
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