Black hole carnivals may produce the signals seen by gravitational-wave detectors
Artist’s impression of a collection of black holes in the core of a star cluster. Credit: ESA/Hubble, N. Bartmann

Black holes crashing into each other have been detected by the LIGO-Virgo- KAGRA Collaboration. Einstein was correct when he said that the waves created by these systems distort space-time with their huge mass. As detector sensitivity improves, we expect to see these crashes on a daily basis in the next observing run. We don't know what causes these crashes.

Massive stars can cause black holes. The death is usually violent, a burst of energy that can destroy or push away objects. It is not easy to form two black holes that are close enough to be merged. The centers of star clusters are a good example of how to push them together.

Black holes that are very far apart can be pushed together. Mass segregation leads the biggest objects to sink into the middle of the well. Black holes should form a dark core in the middle of the cluster. There are two things. Black holes can be influenced by nearby objects if they pair up. The influences can push thebinary closer to eachother.

The properties of merging binaries can be affected by mass segregation in star clusters. The shape of the binaries's orbit is one of the most important properties. Since mergers in star clusters can happen very quickly, the shape of the orbitals can be more like an ellipse than a circle. When two black holes are in an elliptical pattern, the signal from the wave can be studied for clues to where the two objects came from.

A group of OzGrav researchers and alumni are studying the shapes of black holes. Some of the binaries observed by the LIGO-Virgo-KAGRA collaboration have been found by a group led by Dr. Isobel Romero-Shaw. The majority of the observed black holes could have been forged in star clusters.

Dr. Romero-Shaw likes to think of black holes as dance partners. When a pair of black holes evolve in isolation, they are like a couple in a ballroom. It's beautiful but not surprising. There is a carnival-style atmosphere inside a star cluster where you can get lots of different dances happening at the same time. Black hole carnivals in the centers of star clusters are thought to be an important contribution by the results of the study.

The evidence that LIGO–Virgo–KAGRA's black holes form dynamically is increased by four eccentric mergers. There is a document titled "10847/1538-4357/ac9798".

Journal information: Astrophysical Journal