“Neutron stars are the densest matter in the universe, so if you keep adding mass, eventually that will collapse to a black hole, which isn’t matter anymore,” Eric Burns, an assistant professor of astrophysics at Louisiana State University who was not involved in the new work, says. “So that extreme density allows that object to house incredibly powerful magnetic fields. If it wasn’t that dense, the magnetic fields would just rip the star apart.”

Those unique conditions make magnetars rare and their giant flares even rarer. Gamma ray bursts are detected roughly once a month, Mereghetti says, but only three magnetar giant flares have been spotted from within the 100 billion stars within the Milky Way in the last 50 years. Spotting the flares from outside our galaxy is even harder, as you need to be pointing the detector in the right direction and be able to differentiate their radiation from other sources of gamma ray explosions.

Yet for the first time, Merenghetti and his colleagues have managed to do just that. Their hypothesis—a magnetar—seems to have borne fruit and given them a scientific first.

Lives of stars

In a new paper published in Nature, Mereghetti and his team lay out their case that the eruption detected in November, 2023 was the result of a giant flare from a magnetar located in the M82 galaxy, which is 12,000 light-years away. 

“In the past, there have been a few cases of tentative discoveries of giant flairs in external galaxies, but the one that we report is much more convincing just because it’s the most localized, with a much better procedure,” he says.