Messier 72

One of the more distant globular clusters, Messier 72 (M72) lies 53,000 light years away in the Aquarius constellation. It is one of the least dense globular clusters in orbit around our galaxy.

It does, however, contain a significant population of Cepheid variable stars with an estimated 43 such stars. Cepheid variables are stars that vary in brightness in a regular, predictable way. This makes it possible for scientists determine the distance to them.

Globular clusters are ancient. They are many billions of years old—usually 10 to 13 billion years old—almost as old as the universe itself. The stars they contain tend to be very old as well, because star formation inside the cluster has largely ceased. The formation of globular clusters is not well understood. Current research leans toward the idea that they formed from very dense molecular clouds in the early universe. Some larger globular clusters may once have been dwarf galaxies whose larger star populations were stripped away from the core by larger galaxies.

M72

Distance: 53,000 light years

Number of stars: 168,000

Diameter: 106 light years

Age: 9.5 billion years