This Black Hole's Jets Wobble Like Crazy Because It's Warping Space

Pablo Tucker
May 3, 2019

To the left of the clip, a star can be seen being pulled into the black hole.

The year 2019 has been a big one for black holes.

Most black holes are believed to spew jets of plasma from its poles. The study was conducted at Australia's International Centre for Radio Astronomy Research (ICRAR).

This unusual phenomenon causes some of the particles that fall into the black hole to escape through relativistic jets, which are long energetic plasma beams that flow from the black hole's axis of rotation at a rate of more than half the speed of light. The black hole is constantly siphoning material from its stellar companion, and as that material gets sucked in, it forms an accretion disk around the black hole. According to the theory, massive objects, such as black holes, distort space and time, and when they spin, their gravitational influence pulls space and time around with it, also known as frame-dragging. And they have just discovered an fantastic occurrence: relativistic jets wobbling so fast their change in direction can be seen in mere minutes.

Using the Very Long Baseline Array-an intercontinental system of 10 radio telescopes operated from a center in Socorro, New Mexico-the team observed the jets at a high resolution, equivalent to seeing a quarter in NY from the distance of Los Angeles.

As the black hole spins, it drags spacetime around with it, leading to the precession of the inner puffed-up accretion disk, researchers said.

When the ICRAR team studied the black hole they realised the jets were behaving in a way which had never been seen before.

"You can think of it like the wobble of a spinning top as it slows down - only in this case, the wobble is caused by Einstein's theory of general relativity", he said.

It occurred during an extraordinarily bright outburst of a black hole in a binary system (two objects gravitationally bound together) known as V404 Cygni, about 7,800 light years away in the constellation of Cygnus.

According to scientists, V404 Cygni consumes matter from a companion star, whose mass is about 70 per cent that of the Sun.

Tamara Davis, an astrophysicist at the University of Queensland who was not involved in the discovery, said the resolution telescopes could now achieve - and the new ways they are testing how gravity works - are "truly impressive".

Miller-Jones, Tetarenko, and Sivakoff, along with colleagues from around the world, are reporting their results in the scientific journal Nature.

The jets appear to be rapidly rotating with high-speed clouds of plasma - potentially just minutes apart - shooting out of the black hole in different directions.

However, "These jets were changing so fast that in a four-hour image we saw just a blur", said Alex Tetarenko, a recent Ph.D graduate from the University of Alberta and now an East Asian Observatory Fellow working in Hawaii. But these jets were changing so fast that in a four-hour image we just saw a blur.

"Typically, radio telescopes produce a single image from several hours of observation", she said.

Researchers initially thought the jets emitted from Cygni travelled in similar directions but upon closer inspection, determined this was not the case. "It was like trying to take a picture of a waterfall with a one-second long exposure".

"Hot on the heels of our first image of a black hole, this study observes how the gas around a particularly hungry black hole varies with time", Professor Davis said. In addition, that inner section of the accretion disc is puffed up like a solid doughnut that also precesses. "We think the disc of material and the black hole are misaligned".

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