When two galaxies collide they often stop making new stars

When two galaxies collide, it creates a burst of energy that kills off star formation – a process that strangely doesn’t match up with what we see in simulations of galactic smash-ups

Space 29 September 2022

Galaxies merging

Freshly-merged galaxies can stop forming stars

European Space Agency/Hubble & NASA

When galaxies collide, new stars often stop forming. This effect has been predicted by simulations for more than a decade, but observational evidence for it has been sparse and more recent theoretical work has brought it into question. Now, researchers have demonstrated that freshly-merged galaxies are far more likely than peaceful ones to shut down star formation.

Sara Ellison at the University of Victoria in Canada and her colleagues assembled a sample of 508 galaxies that had experienced mergers within the last billion years …

Article amended on 30 September 2022

We have corrected how much more likely merged galaxies were than isolated ones to have undergone a period of rapid star formation, followed by near-total cessation.

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