A strange black hole is making scientists scratch their heads.
The distant object, dubbed "1ES 1927+654" and packing the mass of 1 million suns, previously stunned astronomers when its corona — a billion-degree cloud of rapidly moving particles enveloping a black hole — suddenly vanished. (It's since returned.) Now, scientists have observed flashes of X-rays shooting out from the black hole, and these flashes are speeding up. At first these powerful events happened every 18 minutes; it's now down to seven minutes.
What could be driving this unprecedented observation?
The research, announced at the 245th meeting of the American Astronomical Society and soon to be published in the journal Nature, concludes that the most likely culprit is an object passing profoundly close to the black hole. It's a dead star called a "white dwarf."
"This would be the closest thing we know of around any black hole," Megan Masterson, a physicist at MIT who co-led the research, said in a statement. "This tells us that objects like white dwarfs may be able to live very close to an event horizon for a relatively extended period of time."
Veering close to a black hole is dangerous business. Black holes are profoundly dense. If Earth was (hypothetically) crushed into a black hole, it would be under an inch across. But supermassive black holes are much larger, and this extreme mass makes them gravitationally powerful. Any object that falls past a black hole's point-of-no-return, called the event horizon, isn't coming back. That includes light.
"This would be the closest thing we know of around any black hole."
The astronomers ran simulations of what could drive these unusual bursts of energy around the black hole 1ES 1927+654, which they spotted with the European Space Agency’s XMM-Newton satellite. The most plausible outcome is this brazen white dwarf (the spent core of a sun-like star), which is about one-tenth the mass of our sun. It's shedding its dense, outer layer and triggering these pulses of X-rays, the researchers say. This would explain why the flares are speeding up, as the white dwarf is getting closer to the black hole and moving faster.
But it likely won't fall in.
That's because the shredding of the white dwarf's material has a "kickback" effect, propelling it away from the black hole's event horizon.
"Because white dwarfs are small and compact, they’re very difficult to shred apart, so they can be very close to a black hole," Erin Kara, an associate professor of physics at MIT who coauthored the research, explained. "If this scenario is correct, this white dwarf is right at the turn-around point, and we may see it get further away."
Astronomers plan to keep their eye on this curious black hole, located in deep space some 270 million light-years away. More surprises may await.
