In the sky: the Double Cluster

If you’re in the Northern Hemisphere, as most of you are, then late autumn and early winter is a great time to see some of the most famous objects in the night sky, like the Pleiades, the Andromeda Galaxy, and one of my favorite objects: the Double Cluster. To find the Double Cluster, go outside after sunset and look to the northeast. You should see something like this:

The northeastern autumn sky from the Northern Hemisphere. Image generated by Celestia.

Take note of the yellow circle beneath the well known W-shape of Cassiopeia. You can find the spot in the real sky by following the line of the second and third stars of Cassiopeia. Look there from a dark place, and you can see there are two fuzzy spots side by side. If you look through binoculars, you can see that the spots are made of stars, something like this:

Credit: Chuck Jopson/The Etna Astros

The two spots are really two separate open star clusters together known as the Double Cluster. Open clusters are groups of young stars that formed together. These two clusters are among the youngest in the sky, so almost all of their stars are bright and blue. While they look like they’re close together, one is hundreds of light-years farther away than the other, and they formed about 2 million years apart in time.

The Double Cluster is one of those rare objects that looks good at almost any magnification. Through binoculars, it looks neat because you can see two clusters close together. If you look through a small telescope, it’s even better:

Credit: Andrew Cooper

But if you’re lucky enough to have access to a big telescope of 12 inches’ diameter or more (college astronomy departments and local astronomy clubs are a great place to ask), then the Double Cluster is absolutely stunning.

Okay, so you won’t see quite that many stars using your eyes instead of a camera, but that doesn’t diminish the experience. It’s still one of the most beautiful objects in the sky. Grab the viewing instrument of your choice, and go take a look.


About Alex R. Howe

I'm a full-time astrophysicist and a part-time science fiction writer.
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