Part of the myth of Perseus played out across the northern sky, the tragic figure
of Cassiopeia was the wife of Cepheus and the mother of Andromeda. Her
prominent W-shaped constellation is one of the most immediately recognisable
in the entire sky.
Cassiopeia includes a number of open clusters, but none of these is visible to the
naked eye. Particularly notable are two Messier objects, M52 and, close to Ruchbah in the
sky, M103. Another cluster, the Owl Cluster, can be found near the distant star Phi Cassiopeiae.
All of these clusters are young (no more than 35 million years old), and their distances
range between five and ten thousand light years, in the direction of the Galaxy's rim.
Cassiopeia has been the site of two supernovae in historical times. The first occurred
in 1572, and reached a maximum magnitude of roughly -4, making it brighter than Venus in
the sky. The second took place nearly a century later, leaving a shattered region that
is still detectable today, especially by radio telescopes, and is designated Cassiopeia A.
These stellar explosions took place about 10,000 light years away.