Globular clusters are simultaneously one of the most consistently boring-looking objects in the sky and one of the most scientifically useful. You can use them to understand our galaxy’s history, and now, thanks to giant telescopes, they can also be used to understand the evolution of other galaxies. 

These spherical collections of stars seem to form in a single burst of star formation under very specific conditions, such as in the shocked gas of merging galaxies. Large galaxies like our own have clusters that may have formed in situ and clusters that definitely formed elsewhere and were then stolen.

A new survey of the giant, active galaxy Centaurus A documents the locations of 40,000 globular cluster candidates and recommends studying nearly 2,000 of the best ones. These clusters are within roughly 500 thousand lightyears of the galaxy center, and this is the first time a survey has looked to this great a distance.

By confirming clusters, researchers will be able to better understand the merger history of this clearly disrupted system. As explained by Allison Hughes, the first author of an Astrophysical Journal paper on these results: Globular clusters are interesting because they can be used as tracers of structures and processes in other galaxies where we can’t resolve individual stars. They hold on to chemical signatures, such as the elemental composition of their individual stars, so they tell us something about the environment in which they formed. 

She goes on to further explain: If you see a line of these globular clusters that all have similar metallicity (chemical composition) and move with similar radial velocity, we know they must have come from the same dwarf galaxy or some similar object that collided with Centaurus A and is now in the process of being assimilated.

It’s a galaxy-eat-galaxy universe out there.

Let’s be honest. It’s a galaxy-eat-galaxy, protoplanet-hit-protoplanet, and randomly rearranging solar system out there.

More Information

The University of Arizona press release

“NGC 5128 Globular Cluster Candidates Out to 150 kpc: A Comprehensive Catalog from Gaia and Ground-based Data,” Allison K. Hughes et al., 2021 June 9, The Astrophysical Journal