The monster black hole in galaxy cluster Abell 85 is roughly the size of our solar system, but packs the mass of 40 billion suns.

Key takeaways

  • Massive Discovery: A black hole with the mass of 40 billion suns has been found in the galaxy cluster Abell 85, the largest ever measured.
  • Galaxy Mergers: The enormous black hole resides in Holm 15A, an elliptical galaxy likely formed by the collision of at least eight smaller galaxies.
  • Scientific Confirmation: This finding supports existing theories about quasars, showing how black holes can grow so massive through galactic mergers and accretion.
  • Cored Galaxies: Holm 15A is a “cored galaxy,” a type of massive elliptical galaxy with a faint core, formed by the merging of already large galaxies.
  • Astrophysical Insight: The study enhances understanding of galaxy and black hole evolution, showing the extreme scales involved in cosmic mergers.

Astronomers have discovered the largest black hole ever measured: 40 billion times the mass of the sun, or about two-thirds the mass of all stars in the Milky Way. The huge black hole exists within a giant galaxy that was most likely generated by the collision of at least eight smaller galaxies.

Holm 15A is a massive elliptical galaxy located near the heart of the Abell 85 galaxy cluster. A team of astronomers took a photo of Holm 15A’s stars in orbit around the galaxy’s core black hole and developed a model to assist them determine the black hole mass. The researchers revealed their results in a recent publication, which was submitted to the preprint site arXiv and published in The Astrophysical Journal.

Making monster galaxies

When two spiral galaxies, such as the Milky Way and the neighboring Andromeda Galaxy, collide, they can combine to produce an elliptical galaxy. In crowded settings, like as galaxy clusters, these elliptical galaxies might collide and combine to produce a bigger elliptical galaxy. Their center black holes also merge to generate bigger black holes, capable of propelling massive swathes of surrounding stars to the borders of the newly formed galaxy.

The resulting extra-large elliptical galaxy generally lacks enough gas to produce new stars, so its core appears naked after its black hole consumes neighboring stars. Astronomers call these massive elliptical galaxies with faint cores “cored galaxies.” Massive cored galaxies are frequently seen at the cores of galaxy clusters.

The authors of the current study discovered that Holm 15A, the large galaxy in the heart of its host galaxy cluster, must have evolved via yet another merger of two already massive cored elliptical galaxies. That means Holm 15A was most likely generated billions of years ago by the merger of eight smaller spiral galaxies. Pairs of spiral galaxies generate elliptical galaxies, which in turn form cored elliptical galaxies, and a pair of cored galaxies becomes Holm 15A. This chain of mergers also produced the black hole at its heart, a monster roughly the size of our solar system but with the mass of 40 billion suns.

Explaining quasars

The physicists are ecstatic to discover the largest gigantic black hole ever measured.

“Just imagining a black hole that is so huge is cool,” said Jens Thomas, an astronomer at Germany’s Max Planck Institute for Extraterrestrial Physics and one of the study authors.

However, the discovery is also interesting because it supports scientists’ existing understanding of quasars, which are distant galaxies with giant core black holes that release enormous quantities of light as they consume neighboring matter through a process known as accretion. Astronomers who studied quasars concluded that black holes with 10 billion or more solar masses were required for some of these distant quasars to be so luminous.

“Finally, we managed to find one nearby, which sort of confirms that our idea of how quasars work and how the accretion on black holes can explain them makes sense,” said study author Roberto Saglia, also of the Max Planck Institute.

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