Blackhole As Large As Our Solar System Found In A Nearby Universe
In December of 2019, astronomers at the Max Planck Institute for Extraterrestrial Physics and at the University Observatory announced the discovery of the largest black hole ever measured in the nearby universe at the center of an elliptical galaxy in galaxy cluster Abel 85. It is roughly the size of our solar system (2/3 the mass of the 100-billion stars in the Milky Way).
The galaxy is Holm 15A, a huge elliptical galaxy at the center of a cluster of galaxies called Abell 85, which consists of more than 500 individual galaxies, at a distance of 700 million lightyears from Earth, twice the distance for previous direct black hole mass measurements.
“There are only a few dozen direct mass measurements of supermassive black holes, and never before has it been attempted at such a distance,” explains MPE scientist Jens Thomas, who led the study. “But we already had some idea of the size of the black hole in this particular galaxy, so we tried it.”
“Just imagining a black hole that is so huge is cool,” said Thomas one of the study’s authors.
These huge elliptical galaxies like Holm 15A can collide and merge again to form an even larger elliptical galaxy. Their central black holes combine as well and make larger black holes.
The authors of the study found that Holm 15A, formed from yet another merger of two already-huge cored elliptical galaxies that probably formed from the combination of eight smaller spiral galaxies over billions of years. Holm 15A is similar to elliptical galaxy M87, the largest, most massive galaxy in the nearby universe, thought to have been formed by the merging of 100 or so smaller galaxies.
“A medium-sized galaxy fell through the center of M87, and as a consequence of the enormous gravitational tidal forces, its stars are now scattered over a region that is 100 times larger than the original galaxy!” said Ortwin Gerhard, head of the dynamics group at the Max Planck Institute for Extraterrestrial Physics about the monster elliptical galaxy that harbors the now iconic black hole the size of our solar system imaged for the first time ever by the Event Horizon Telescope (EHT) on April 10, 2019.