Intergalactic Wanderer

The population of our home galaxy, the Milky Way, includes about 150 globular clusters. And for a long time, astronomers thought all of these giant balls of stars were pretty much alike. But in the last couple of decades, they’ve discovered that each one is unique.

One example is NGC 2419. It’s about 300,000 light-years away, making it one of the galaxy’s most remote globulars. When its distance was first measured, in fact, astronomers thought the cluster was too far to be tied to the Milky Way. So they called it the Intergalactic Wanderer. But it really is part of the Milky Way — far beyond the galaxy’s disk, in a region known as the halo.

The stars in most globulars were all born at the same time. But NGC 2419 has two different populations of stars. The stars in one group have a lot more helium and a few other elements than those in the other. The helium-rich stars are clumped in the cluster’s core.

So far, astronomers aren’t sure what that means. There doesn’t seem to be a way to make two separate groups of stars in a globular. That could mean that NGC 2419 formed in a different way from other globulars — a unique formula for a big star cluster.

NGC 2419 is in the constellation Lynx, which is in the northeast as night falls. The cluster is close to the upper left of Castor and Pollux, the twin stars of Gemini. Despite its distance, it’s an easy target for small telescopes.

Script by Damond Benningfield