Strange New Behaviors from a Gigantic Black Hole

One possible explanation is that the corona is oscillating. However, researchers believe the most likely culprit is a spinning white dwarf—an extremely compact core of a dead star orbiting around the black hole and getting closer to its event horizon, the boundary beyond which nothing can escape its gravitational pull. Circling closer would mean moving faster, which explains the increasing frequency of x-ray oscillations.

If this is the case, the white dwarf could be approaching the black hole’s edge without falling in. “This would be the closest thing we know of around any black hole,” says Megan Masterson, a graduate student in physics at MIT, who reported the findings with associate professor Erin Kara and others.

If a white dwarf is responsible for the mysterious flashing, it may also be expected to emit gravitational waves, which can be detected by next-generation observatories such as the Laser Interferometer Space Antenna (LISA) planned for launch in the mid-2030s.

“The one thing I’ve learned with this source is to never stop looking at it, because it will probably teach us something new,” Masterson says. “The next step is just to keep our eyes open.”