Examples of Open Clusters
The best known open cluster is the group known as the Pleiades, or M45, in the constellation Taurus.
This cluster lies about 120 parsecs from Earth, and occupies a volume
of space about 4 parsecs across. There are some 3000 stars in the Pleiades. Six are
bright enough to be visible without a telescope.
This is a moderately young cluster, about 100 million years
old. To set that in perspective, this is about 50 times younger than our Sun.
Long exposure images of the Pleiades show considerable nebulosity (fuzziness caused by surrounding gas
and dust), as can be seen in the image shown here. These are
reflection nebulae (clouds of gas and dust that shine by reflected light)
that are being illuminated by the bright stars of the cluster.
