Astronomers are seeing two galaxies locked in an epic 'battle' of sorts, charging at each other at speeds of 500 km/s, smashing into each other and then going at it again.
During each collision, one galaxy hits the other with a blast of intense radiation.
What's more, these radioactive blows hinder the damaged galaxy's ability to form new stars.
The team behind this discovery used observations from the European Southern Observatory’s Very Large Telescope and the Atacama Large Millimeter/submillimeter Array.
A secret weapon: a supermassive black hole
Galaxy mergers and collisions aren't uncommon: they're a symptom of a constantly moving Universe, where gravity causes objects in deep space to interact with one another.
"We call this system the 'cosmic joust'," says Pasquier Noterdaeme, a researcher at the Institut d'Astrophysique de Paris, France.
However, normally during a joust or duel, both parties have an equal chance to become the victor.
In this case, one of the galaxies has an unfair advantage, in the shape of a quasar that's blasting out a spear of radiation into the other galaxy's heart
Quasars are the bright cores of galaxies powered by supermassive black holes, which release huge amounts of radiation and cause those galactic cores to shine.
Both quasars and galaxy mergers were more common in the early Universe, within the first few billion years after the Big Bang.
But astronomers can use a pretty neat trick of physics to see them.
Because it takes time for light from distant galaxies to travel billions of lightyears across an ever-expanding Universe, by observing deep into space, astronomers can look back in time.
The light from these colliding galaxies took over 11 billion years to reach us, so astronomers are seeing them as they existed when the Universe was only 18% of its current age.
"Here we see for the first time the effect of a quasar’s radiation directly on the internal structure of the gas in an otherwise regular galaxy," explains study co-lead Sergei Balashev, who is a researcher at the Ioffe Institute in St Petersburg, Russia.
The observations show radiation fired out by the quasar disrupts clouds of gas and dust in the other galaxy, leaving only the smallest, densest regions behind.
And these regions are likely too small to be able to form new stars, leaving the galaxy wounded and less able to regenerate.
"These mergers are thought to bring huge amounts of gas to supermassive black holes residing in galaxy centres," says Balashev.
In other words, the battle between the galaxies causes fuel to be fed directly into the black hole powering the quasar, making it stronger and more powerful.
