Extra-galactic Globular Clusters

Globular clusters are, as the name suggests, stars clustering together in a roughly spherical ensemble. Each cluster contains between a few tens of thousands and a few million stars. Our Milky Way galaxy has around a couple of hundred of them in orbit around it, which is a fairly typical number for a large spiral galaxy like ours. Some galaxies have very few, if any. Others possess thousands, well over ten thousand in the case of M87, which is a giant elliptical galaxy in the Virgo cluster of galaxies.

Many, many amateur astronomers have published pictures of globular clusters which belong to our galaxy and I've taken a few myself. Here is an example: M2 in Aquarius. Not many people go in search of globular clusters which orbit other galaxies. I started this project through incompetence. Soon after taking over Tacande Observatory, and still learning how to drive everything, I tried to point the telescope at a variable star, AE And in the Andromeda galaxy which is also known as Messier 31 or M31, but missed the target. Rather than discard the image, I examined it to see what it contained — I already knew what was not there. It showed eight globular clusters.

So far I've taken images which show globular clusters around three external galaxies: M31 (as mentioned above), M87 and M81 which is a spiral galaxy in the constellation Ursa Major and one of the closest outside the local group of galaxies.

A distant globular cluster, NGC 2419, in the constellation Lynx was long thought to be an extragalactic object but it is now known to be in orbit around the Milky Way. Nonetheless, it is included here because it is further away from us than are the Magellanic Clouds and they are undoubtedly extragalactic objects.