The Double Cluster in Perseus,
h and Chi Persei (Chi on the left), are young clusters
of stars only about 13 million years old
that are moving through space together.
At a distance of 7650 light years (accurate
to 2%), and dimmed by 1.8 magnitudes by absorption
of starlight by interstellar dust, they are just barely
visible to the naked eye to the east of the "W" of Cassiopeia. The clusters represent one
of the few cases where Greek letter names were applied
to astronomical objects other than specific stars. Chi
Persei is the cluster to the right. When Bayer ran out
of Greek letters, he used Roman letters; which are
only rarely now used.
Photo by Mark Killion.
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