Face the northwestern horizon this evening – above and to the right of the place where the sun set on the western horizon – but mid- to late evening. Here you can find the Double Cluster in the constellation Perseus. These are two open stars clusters, known as “H” and “Chi” Persei (also called NGC 884 and 869).
How to find them? First, you need a dark sky. As you work your way up from the northwest horizon you’ll see the famous constellation Cassiopeia forming a backwards “3,” or perhaps the letter “M” or “W” turned on its side. Just above Cassiopeia, assuming your sky is dark enough, you’ll see a somewhat large fuzzy patch. This is the Double Cluster.
These two open star clusters are an estimated 7,400 light years away. Each contains 300 to 400 stars. These stars are thought to be approximately three million years old … babies in star time! The stellar gas and background stars that compose the flat disk of our Milky Way galaxy lie behind the clusters. Thus (again, if your sky is dark enough), you’ll see the hazy pathway of the winter Milky Way crossing this part of the sky.
The Double Cluster was charted by skywatchers as early 150 B.C. Hipparchus saw it, and Ptolemy named it as one of seven “nebulosities” in the Almagest, an ancient astronomy text used for over a millennium. The Double Cluster is a favorite amongst stargazers. It is a marvelous place to scan with binoculars.
Written by Deborah ByrdPrint This Post