Astronomers have just discovered one of the biggest black holes ever. Even more surprising, though, is where they found it — and the strange reason it got so big. The newly discovered black hole tips the scales at more than 17 billion times the size of our sun, making it one of the largest ever found. Supermassive black holes, even of this size, are not totally unknown — the largest ever observed is slightly bigger at 21 billion times the size of our sun.
Usually, black holes this big are found at the centre of a giant galaxy cluster. This supermassive black hole, however, was found in a modestly-sized elliptical galaxy, with only a handful of surrounding galaxies nearby. It's a finding so unlikely that researcher Chung-Pei Ma of the University of California-Berkeley compared it to running across a single skyscraper surrounded by cornfields.
The researchers have come up with a theory that could explain not only the black hole's size but also how it came to be: This supermassive black hole is actually two black holes, which combined long, long ago when two galaxies collided. Eventually, the edges of the two black holes were warped so much by each other that they merged into one incredibly large supermassive black hole, the full simulation of which you can see right here:
Computer simulation of the newly discovered supermassive black hole / NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel (STScI)