Free Astronomy Magazine July-August 2025

36 JULY-AUGUST 2025 ASTRO PUBLISHING Noterdaeme, a researcher at the In- stitut d’Astrophysique de Paris, France, and the French-Chilean Laboratory for Astronomy in Chile, drawing a comparison to the me- dieval sport. But these galactic knights aren’t exactly chivalrous, and one has a very unfair advan- tage: it uses a quasar to pierce its opponent with a spear of radiation. Quasars are the bright cores of some distant galaxies that are pow- ered by supermassive black holes, releasing huge amounts of radia- tion. Both quasars and galaxy merg- ers used to be far more common, appearing more frequently in the Universe’s first few billion years, so to observe them astronomers peer into the distant past with powerful I n the distant depths of the Uni- verse, two galaxies are locked in a thrilling war. Over and over, they charge towards each other at speeds of 500 km/s on a violent col- lision course, only to land a glanc- ing blow before retreating and winding up for another round. “We hence call this system the ‘cosmic joust’,” says study co-lead Pasquier by ESO Bárbara Ferreira A pair of galaxies in deep-space battle