When black holes collide

Merging galaxies

Two galaxies crash into each other, initially producing a confused mess of material but then settling down to become a single, merged galaxy.

Two black holes

The black holes that started at the centres of the original galaxies gradually spiral towards each other, eventually coalescing.

High-energy jet

The combined black hole may cause the core of the merged galaxy to eject streams of hot gas and high-speed particles.

Visible consequences

The newly merged black hole gives its presence away through the release of gravitational waves and high-energy radiation.