There are a lot of galaxies in the universe — billions and billions of them, in fact. And many of them are in the process of collision: some collided long ago, some are merging right now, and some will slam together in the distant future. When they collide, the supermassive black holes in their cores can collide and merge too — and that's a pretty extreme event. Studying how fast these mergers take place is changing astronomers’ models of galaxy formation and evolution.

Want to help us make Syzygy even better?
Tell your friends and give us a review, or show your support on Patreon: patreon.com/syzygypod

Huge thanks to our patrons, listed over on the Cosmic Great Wall of Gratitude

Syzygy is produced by Dr Chris Stewart and co-hosted by Dr Emily Brunsden from the Department of Physics at the University of York.

On the web: syzygy.fm | Twitter: @syzygypod

Things we talk about in this episode:

The merging galaxies paper: https://www.nature.com/articles/s41586-018-0652-7

Hubblesite article about the story: https://www.nasa.gov/feature/goddard/2018/astronomers-unveil-growing-black-holes-in-colliding-galaxies

Simulations of galaxy collisions: https://svs.gsfc.nasa.gov/10687

Stephan’s Quintet: https://apod.nasa.gov/apod/ap140327.html

Keck Observatory: http://www.keckobservatory.org

Gravitational wave discovery: https://www.ligo.caltech.edu/news/ligo20170927

Simulations of SMBH mergers: https://www.space.com/42017-merging-supermassive-black-holes-eerie-glow.html