Messier 54

For two centuries, astronomers thought Messier 54 (M54) belonged to our galaxy. Although relatively close to the Milky Way galaxy, Messier 54 actually belongs to another galaxy—the Sagittarius Dwarf Elliptical Galaxy. Nevertheless, it is destined to become part of our galaxy as the gravity from the 400 billion stars draws it in along with its dwarf galaxy.

In 2009, scientists uncovered evidence of the first intermediate-mass black hole ever found in a globular cluster. It is estimated to have a mass of 9,400 suns.

Globular clusters are ancient collections of stars that are gravitationally bound together in a spheroidal shape. Some are almost as old as the universe itself. They can contain anywhere from tens of thousands of stars to millions of stars. The stars they house 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.

M54 Facts

Distance: 90,000 light years

Number of stars: 1,000,000+

Diameter: 306 light years

Age: 13 billion years