The Strangest Black Holes in the Universe. Cannibalistic Black Holes. Black holes devour anything unlucky enough to drift too close, including other black holes. Scientists recently detected the monstrous black hole at the heart of one galaxy getting consumed by a still larger black hole in another.
The discovery is the first of its kind. Astronomers had witnessed the final stages of the merging of galaxies of equal mass — so-called major mergers — but minor mergers between galaxies and smaller companions had long eluded researchers.
Using NASA's Chandra X-ray Observatory, investigators detected two black holes at the center of a galaxy dubbed NGC3393, with one black hole about 30 million times the mass of the sun and the other at least 1 million times the mass of the sun, separated from each other by only about 490 light-years.https://www.space.com/15941-strangest-black-holes-universe-countdown.html