Dust-shrouded Milky Way star cluster may be nearly as old as the universe

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Astronomers have determined that VVV CL001, a metal-poor globular cluster near the center of the Milky Way, is about 13.4 billion years old, making it one of the oldest known star clusters in our galaxy. The cluster lies behind thick clouds of interstellar dust, which made its distance and age difficult to establish.

The paper, outlining the methodology for estimating its age and distance, was posted to the arXiv preprint server on Oct. 20. It has been accepted for publication by Astronomy & Astrophysics. Globular clusters are some of the oldest members of the Milky Way and hold clues to how our galaxy first formed.

These star clusters are home to stars that are 10 billion to 13 billion years old, which preserve fossil records of the conditions under which our galaxy first assembled. A cluster's age and chemical properties can be used to put a limit on our galaxy's age. Because older clusters generally have low metal content, astronomers study metal-poor globular clusters to determine their precise ages.

One such metal-poor globular cluster, called VVV CL001, was discovered by the VISTA Variables in the Vía Láctea Survey (VVV) in 2010. "It was observed as a low-mass, low-luminosity stellar group in the inner bulge region…," researchers write in the paper. It was confirmed as a cluster in 2019.

Interestingly, this star cluster appears very close to the galaxy's center. But researchers found that it is moving toward us at a very different speed than other stars in that area and thought that it might not really belong there. To find out where it came from, researchers examined its path around the galaxy.

Since its orbit depends on how far away the cluster is, different studies assumed different distances and got different paths. The main culprit turned out to be the uncertainty in measuring the actual distance. Measuring the cluster's distance is tricky because it sits in a crowded region where dust dims starlight.