Trumpler 1, Open Star Cluster
The star cluster "Trumpler 1" is located at a distance of about 8,200 light-years in the constellation Cassiopeia, just 40' away from "Messier 103".
With an apparent size of 4.5' its true diameter is calculated to be 10 light-years. It is classified as II2p, which means that it contains less
than 50 stars. The brightest of them reach the 10th magnitude. This corresponds to an absolute brightness of M=-2.2mag and a luminosity of 600
suns. The second brightest star in "Trumpler 1" is a double star named "WDS 01356+6117". The two 10.7mag and 10.9mag bright components
are currently (2006) 1.2 arcseconds apart. The distance between the two stars appears to be slowly increasing over the years.
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Even in my 20 inch telescope "Trumpler 1" is not a spectacular sight. Since the star cluster is not very large, you can easily magnify to 270x. The
first thing that catches your eye is a straight line formed by four equidistant stars. This line dominates the appearance of the cluster. On of the stars
is a very close double star, but at 270x it can be separated without problems. There are about 15 to 20 more fainter stars visible.
If you are observing Messier 103, a short detour to Trumpler 1 is still worthwhile.
