Astronomers have detected a record-breaking X-ray flare from a supermassive black hole, 1ES 1927+654, about 100 million light-years from Earth. This black hole with a mass roughly a million times larger than the sun has shown truly extraordinary activity with pulses of X-rays accelerating over two years, from an interval of 18 minutes to only seven minutes.
This phenomenon, detected by researchers from MIT and other institutions, is believed to be caused by a spinning white dwarf orbiting dangerously close to the black hole’s event horizon. Such proximity is rare, as objects approaching the event horizon typically succumb to the black hole’s immense gravitational pull.
This would be the closest thing that we know of around any black hole,” says MIT graduate student Megan Masterson and co-lead author of the paper. That might mean a white dwarf has managed to remain there for hundreds or thousands of years.
The results were presented to the 245th meeting of the American Astronomical Society, and published in Nature. An X-ray burst could be driven by a white dwarf, allowing it to release detectable gravitational waves, thus potentially observable through future instruments including NASA’s Laser Interferometer Space Antenna.
The unusual activity of 1ES 1927+654 first caught attention in 2018 when its corona—a cloud of superheated plasma—unexpectedly vanished and reformed months later. Afterward, the reassembled corona emitted exceptionally bright X-rays, prompting continued monitoring.
In 2022, the European Space Agency’s XMM-Newton observatory revealed quasi-periodic oscillations in the X-ray emissions. While such oscillations have been noted in a few other black holes, the rapid increase in frequency over time is unique.
The X-ray source is relatively close to the event horizon of the black hole. X-rays are usually emitted by hot plasma in the innermost regions of a black hole, while optical and ultraviolet light come from cooler, outer regions.
“This variability suggests a source close to the event horizon, possibly orbiting in a precarious balance,” said Erin Kara, associate professor at MIT.
The discovery sheds light on the complexity of black hole dynamics and can open new avenues for studying extreme cosmic phenomena both through electromagnetic and gravitational observations.
