Scientists spot giant galaxy clusters preparing for second crash

By Dean Murray

Space scientists have captured a rare cosmic event: two galaxy clusters have collided and are poised to smash into each other again.

Galaxy clusters are some of the largest structures in the universe, containing hundreds or thousands of individual galaxies, massive amounts of superheated gas, and invisible dark matter.

New observations from NASA’s Chandra X-ray Observatory and other telescopes show that the two galaxy clusters involved in the collision, collectively known as PSZ2 G181 and about 2.8 billion light-years from Earth, collided about a billion years ago.

More from this section

Horrific hit-and-run leaves man unable to remember his name

FIFA’s Haiti jersey ban echoes the long campaign to discredit and downplay the Haitian Revolution

Trump’s US-Iran ceasefire deal is a costly return to prewar conditions – and resolving nuclear questions will run into the ‘indivisibility problem’

The event caused structures that researchers say are probably shock fronts — similar to those created by jets that have broken the sound barrier.

Since the collision, the clusters have continued traveling outwards and are currently separated by about 11 million light-years, the largest separation of these kinds of structures that astronomers have ever seen.

NASA explains: "Now, data from NASA’s Chandra and ESA’s XMM-Newton is providing evidence that PSZ2 G181 is poised for another collision. Having a first pass at ramming each other, the two clusters have slowed down and begun heading back toward a second crash."

A paper describing these results appears in a recent issue of The Astrophysical Journal (ApJ) and is led by Andra Stroe from the Center for Astrophysics | Harvard & Smithsonian (CfA) and collaborators. It is part of a series of three papers in ApJ.