Holm 15A is not just any galaxy—it is the product of multiple mergers over billions of years. When two spiral galaxies collide, they form an elliptical galaxy. In dense galaxy clusters, these elliptical galaxies can merge again, growing even larger. Holm 15A likely formed from the combination of eight smaller galaxies, leading to the creation of its supermassive black hole.

As galaxies merge, their central black holes also merge, gradually forming a larger singularity. This process can eject nearby stars, creating a galaxy with a faint central region—astronomers refer to these as “cored galaxies.” Holm 15A, a prime example of this phenomenon, sits at the heart of the Abell 85 cluster.

Supporting Quasar Theories

The discovery of this enormous black hole provides strong evidence for existing models of quasars—distant galaxies with intensely bright centers powered by supermassive black holes. Astronomers have long theorized that quasars must contain black holes with masses exceeding 10 billion suns to account for their extreme brightness. This study confirms that such massive black holes exist, supporting current theories of how quasars form and operate.

“Just imagining a black hole that is so huge is cool,” said Jens Thomas, an astronomer at the Max Planck Institute for Extraterrestrial Physics and a co-author of the study. His colleague Roberto Saglia added, “Finally, we managed to find one nearby, which sort of confirms that our idea of how quasars work makes sense.”

This discovery is a crucial step in understanding the growth of galaxies and the role of black holes in shaping the universe. With future observations, astronomers hope to uncover even larger black holes and further refine their models of galaxy evolution.