Most Massive Black Hole in Nearby Universe With 40 Billion Solar Masses Discovered

Astronomers have discovered a monster black hole with a mass 40 billion times that of our sun, which takes the record for most massive in the local universe—the region of space around us with a radius of approximately one billion light-years.

According to a study published in The Astrophysical Journal, the ultra-massive black hole is located at the heart of a galaxy called Holm 15A. This galaxy is itself located in the center of a large cluster of 500 individual galaxies known as Abell 85, which is located around 700 million light-years from Earth.

The authors of the study, from the Max Planck Institute for Extraterrestrial Physics (MPE) and the University Observatory Munich (USM) in Germany, became interested in Holm 15A due to some unusual characteristics.

Despite the fact the galaxy is the brightest in the cluster overall, its center is extremely faint and diffuse, indicating the presence of a black hole with a very high mass.

"The central region of Holm 15A has a very low surface brightness, i.e. luminosity per area on the sky," Roberto Saglia, an author of the study from MPE, told Newsweek. "We knew from our past studies that such low central surface brightnesses in big galaxies are a signature produced by the merging of two supermassive black holes; so, when we saw that Holm 15A had such a surface brightness profile, we realized that only a huge central black hole could have produced it."

Observations conducted using USM's Wendelstein Observatory and the Very Large Telescope in Chile's Atacama Desert enabled the team to estimate the black hole's mass to 40 billion suns based on the motions of stars around the galactic center.

"We measured the black hole by taking spectra of the central region of the galaxy. They showed us how quickly the stars around the black hole were moving under the gravitational force produced by the black hole. From this, using Newton's law, one can derive the mass of the black hole," Saglia said.

"Imagine condensing two-thirds of the Milky Way—which has a stellar mass equivalent to 60 billion suns—into a black hole and you have what we measured," he said.

Abell 85 cluster of galaxies
Image of the Abell 85 cluster of galaxies obtained at the USM Wendelstein observatory. Matthias Kluge/USM/MPE

According to the researchers, measuring the mass of a black hole in this way has never been attempted before at such a distance.

"But we already had some idea of the size of the black hole in this particular galaxy, so we tried it," Jens Thomas, lead author of the study, from MPE said in the statement.

While the black hole at the center of Holm 15A is certainly huge, it is not the most massive ever to be identified. That title goes to an object known as TON 618, which has an estimated 66 million solar masses.

The local universe is the section of the cosmos that can be observed in the most detail, according to the University of Wisconsin-Madison Department of Astronomy. Thus most of our knowledge about the universe comes from this region.