Astronomers have clocked a spectacular galactic collision. at an astonishing speed of 3.2 million km/h (2 million mph). The place where this high-speed smash occurs is Stephan’s Quintet, a cluster of five galaxies discovered by French astronomer Édouard Stephan in 1877. Contrary to what its name might suggest, the Quintet is a dramatic display of galactic chaos; debris scatters about like cosmic wreckage.
Four of the galaxies are currently colliding and merging over millions of years. They include the one, NGC 7318b, currently plowing through the group at high speed and creating a wake of shocked space. This shock wave, moving at hypersonic speeds through cold gas, ionizes the atoms creating glowing trails of charged gas. We see this particularly vividly in the blue regions of baby stars being born. Fainter, larger, redder patches are also observed: these are galaxies at vast distances behind the cluster. We could be looking at a similar mind-boggling scale of creation and destruction, but we would never know. That light took all that time to reach us, and by now humans walked on the moon, so there’s no way to check.
This dramatic collision was uncovered using WEAVE, a cutting-edge spectrograph on the William Herschel Telescope in Spain, alongside data from LOFAR, the Very Large Array, and the James Webb Space Telescope. Dr. Marina Arnaudova, lead researcher, described the dual nature of the shockwave: “It moves at hypersonic speeds in cold gas, ripping apart electrons, but compresses hot gas, emitting radio signals.”
Interestingly, though dubbed a “quintet,” only four galaxies are colliding. The fifth, a photobombing galaxy, lies 200 million light-years closer to Earth. This amazing discovery is WEAVE’s first and the beginning of its prospective galactic scientific contribution. By using these findings, the team wants to provide a clear picture of the constantly shifting dynamics of our universe and solve the puzzles of galactic origin and evolution.