Cosmic Joust: Two Ancient Galaxies Clash Before a Titanic Merger

In a stunning discovery, astronomers have captured a rare glimpse of two ancient galaxies on a high-speed collision course, locked in a cosmic duel that will ultimately end in a spectacular merger. The scene, which unfolded around 11.4 billion years ago, when the universe was barely a fifth of its current age, has been likened to a medieval joust — with one galaxy unleashing a powerful beam of radiation, striking its companion like a cosmic lance.

The galactic pair, both roughly as massive as our Milky Way, were observed using two of Chile’s most powerful observatories: the Atacama Large Millimeter/submillimeter Array (ALMA) and the European Southern Observatory’s Very Large Telescope (VLT).

At the core of one of these galaxies lies a quasar — a brilliant, high-energy object powered by a supermassive black hole approximately 200 million times the mass of our Sun. The quasar emits intense radiation that, in this case, pierced directly through the other galaxy. The ultraviolet light from the quasar’s beam disrupted vast clouds of gas — the very raw material from which stars are born — breaking them into tiny, dense fragments too small to trigger star formation.

“It’s the first time we’ve seen a quasar actively sabotage star formation in another galaxy,” noted astrophysicist Sergei Balashev, co-lead of the study. His team reported their findings in the latest issue of Nature.

This high-stakes cosmic encounter is more than just a galactic spectacle. It’s a crucial piece of the puzzle in understanding how galaxies evolve through mergers — a common fate in the universe’s history. Most mergers that astronomers have documented occurred much later, making this ancient duel a particularly valuable snapshot of the early, chaotic universe.

The violent interaction reminded researchers of knights charging in a tournament, with one wielding a deadly weapon. Pasquier Noterdaeme, co-author and astronomer at the Paris Institute of Astrophysics, described it vividly: “Much like jousting knights charging toward one another, these galaxies are rapidly approaching. One of them — the quasar host — emits a powerful beam of radiation that pierces the companion galaxy, like a lance. This radiation ‘wounds’ its opponent as it disrupts the gas.”

Eventually, as gravity continues to draw them closer, the two galaxies will merge into a larger, single system. The quasar, having consumed its available fuel, will dim, leaving behind a reshaped galactic remnant.