Astronomers have found a swarm of black holes speeding through the Milky Way. What does this mean for our galaxy?

Astronomers have studied the globular star cluster Palomar 5 and the stream of stars that is leaving this cluster. It extends approximately 30,000 light-years and is located about 80,000 light-years away from us. Globular star clusters are considered "fossils" of the early Universe, as they typically contain hundreds of thousands of stars that are nearly as old as the Universe itself. In the globular star cluster Palomar 5, astronomers discovered a swarm of stellar-mass black holes racing through our galaxy. This research has been published in the journal Nature Astronomy, as reported by ScienceAlert.

While globular star clusters are fascinating on their own, astronomers are even more intrigued by the long streams of stars that stretch vast distances across the Milky Way. Previously, scientists were unaware of the origins of these streams, but the Gaia space telescope has helped clarify their origins. It is believed that these stellar streams consist of stars that are ejected from globular star clusters during their destruction.

The best example for studying the nature of long stellar streams, according to scientists, is the one associated with Palomar 5. Therefore, it has been examined in greater detail. Astronomers utilized modeling to recreate the orbits and evolution of each star in the cluster to see how they ended up where they are today.

Recent findings suggest that stellar-mass black holes may exist at the centers of globular star clusters, and the gravity of these black holes could contribute to stars escaping from the cluster. Consequently, astronomers included black holes in their modeling.

The results indicated that the presence of hundreds of stellar-mass black holes within the globular star cluster Palomar 5 could have led to its current configuration.

Researchers believe that the gravity of the black holes could have ejected stars from the cluster, creating a long stellar stream. Furthermore, scientists estimate that there are approximately three times more black holes in the star cluster than previously thought. Calculations suggest that these black holes have significant mass and could account for up to 20% of the cluster's current mass, considering that most of its stars are located in the stellar stream.

Astronomers believe that each black hole was formed as a result of supernova explosions at the end of massive stars' lives, when the cluster was still very young. Each black hole has a mass about 20 times greater than that of the Sun.

Modeling has shown that the star cluster Palomar 5 will completely disintegrate in about 1 billion years. However, before this occurs, the star cluster will consist entirely of black holes that are orbiting around the center of the Milky Way.