A supermassive black hole an estimated 100 million light-years from Earth recently performed a vanishing act for stunned astronomers. Now it has reappeared, according to a study published July 16 in The Astrophysical Journal Letters.
The density of black holes prevents light from escaping. But a visible disk of fast-moving, super hot particles called a corona swirls around a black hole. The corona of this particular black hole emitted an unexpected flash of light in 2018 that increased its luminosity by 40 times. Then, over the course of less than a year, it dimmed until it became undetectable. “It even changed by a factor of 100 in eight hours, which is just totally unheard of and really mind-boggling,” said Erin Kara, one of the astronomers from the Massachusetts Institute of Technology.
Scientists think a wayward star may have gotten trapped in the black hole’s gravitational pull. The force of gravity would have shredded the star and flung its debris across the corona, accounting for the sudden flash. It could also have triggered all of the material in the disk to plummet into the black hole or thrown off the disk’s magnetic field so that it could no longer generate and support such high-energy particles.
Now the black hole has slowly begun to pull material from its outer edges together to rebuild its corona. The astronomers say they will continue to keep an eye on this surprising celestial object. “It’s still in this unusual high-flux state, and maybe it’ll do something crazy again, so we don’t want to miss that,” Kara said. —J.B.