Enjoy These Five Brilliant Star Clusters

What do you call a bunch of stars in the same place? No, not the Oscars — we’re talking about star clusters, groupings of hundreds to millions of stars bound together by gravity.

Star clusters come in two varieties: open clusters and globular clusters. Open clusters form when clouds of dust and gas collapse, creating perhaps a few hundred stars. They’re smaller and less dense than globular clusters, and their members are typically younger and brighter. Around 4.6 billion years ago, our Sun was born within an open cluster. Since then, its stellar companions have scattered across the Milky Way.

The formation of globular clusters, on the other hand, is less clear. They can have more than a million stars packed into an area of as little as ten light-years. In comparison, there are only about twelve stars within ten light-years of the Sun. The stars are usually older and dimmer, though the cluster as a whole can be quite luminous. Although a few globular clusters can be seen with the naked eye, you’ll need a telescope to peer within their starry depths.

Here’s five star clusters, open and globular, to observe this week.

Image captured by Unistellar eVscope user John Pickering (New Zealand)

Omega Centauri

The Milky Way’s largest known globular cluster, Omega Centauri (NGC 5139), is thought to be the remnant of a formerly independent dwarf galaxy swallowed by our own. An estimated 10 million stars circulate within the cluster.

Wild Duck Cluster

Named because its shape resembles the flying V of migrating waterfowl, the Wild Duck Cluster is one of the largest open clusters. Also called Messier 11, this star cluster is found in the constellation Scutum.

Image captured by Unistellar eVscope user John Pickering (New Zealand)

Great Pegasus Cluster

Old, bright and packed tight, this globular cluster in the constellation Pegasus sits some 33,000 light-years from Earth. The Great Pegasus Cluster (Messier 15) has undergone what’s called core collapse, where its central stars condense even more tightly together.

Image captured by Unistellar eVscope user Gerd Waloszek (Germany)

Messier 71

This small star cluster was thought to be an open cluster for many years. But further observations revealed Messier 71 to be a young, relatively loosely-packed globular cluster.

Image captured by Unistellar eVscope user David Rowe (United Kingdom)

NGC 188

This open cluster’s extreme age is unusual. Like school friends losing touch, most open clusters drift apart as their stars migrate away from where they were born. However, NGC 188 (also known as Caldwell 1) orbits high above our galactic plane, letting it remain together for some seven billion years.

We encourage you to share your observations and join the conversation through our Facebook, Instagram and Twitter pages using the hashtag #UnistellarChallenge!

If you’d like to send us your observations by email, send them to [email protected].

Clear skies! 🔭