Massive Black Holes Found Abundant in Star Cluster Palomar 5 by Astronomers

In the vast expanse of the Milky Way, a unique globular cluster named Palomar 5 is shedding light on the formation of thin stellar streams and the role of black holes in the evolution of such celestial bodies.

Discovered in 1950, Palomar 5 is located approximately 80,000 light-years away in the Serpens constellation. This cluster, which is about 10 times less massive and 5 times more extended than a typical globular cluster, has been the subject of recent studies due to its prominent tidal tails. These tails provide a clear example to understand how stellar streams form from the gravitational disruption of clusters.

A new study, published in the prestigious journal Nature Astronomy, has revealed some surprising findings about Palomar 5. The study, conducted by a team of researchers including Andreas Koch and Kathryn V. Johnston, suggests that more than 20% of the total cluster mass is made up of black holes. This is three times larger than expected from the number of stars.

The study challenges the traditional understanding of black hole formation and their role in the evolution of globular clusters. It suggests that the current high black hole fraction in Palomar 5 is a result of the dynamical evolution of the cluster. The authors found that black holes dynamically puffed up the cluster over time, a phenomenon that could have implications for our understanding of the evolution and structure of other globular clusters in the universe.

Palomar 5, which is older than 10 billion years and is in the final stages of dissolution, is expected to consist entirely of black holes just before it completely dissolves, roughly a billion years from now. Each black hole in the cluster has a mass approximately 20 times that of the Sun.

The findings of this study provide valuable insights into the role of black holes in the evolution of globular clusters. By studying Palomar 5, researchers hope to gain a better understanding of the formation of thin stellar streams in the Milky Way and the complex interplay between gravity, stars, and black holes in shaping the structure of our galaxy.

For those interested in delving deeper into the study, the DOI is 10.1038/s41550-021-01392-2. This research underscores the importance of continued study and observation of celestial bodies like Palomar 5, as they offer valuable insights into the mysteries of our universe.