Published: Wed, May 01, 2019
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Astronomers witness "one of the most extraordinary black hole systems"

Astronomers witness

Almost 8,000 light-years away from Earth, astronomers have discovered a black hole that keeps rapidly swinging out jets of plasma clouds into space, according to a new study.

V404 Cygni was first identified as a black hole in 1989 when it released a big outburst of jets and radiation. This happened in a way which has never been seen before. 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. It's no longer spinning straight, it's wobbling all over the place.

The study, which was led by the International Center for Radio Astronomy Research (ICRAR), was published today in the journal Nature.

This odd 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.

If the binary orbit is not aligned with the black hole spin axis, this frame dragging will cause the puffed up inner disk to precess - it wobbles around like a spinning top that is slowing down.

When it comes to black holes' relativistic jets, their origins remain a bit of a mystery - not just for V404 Cygni, but for all black holes.

'This is one of the most extraordinary black hole systems I've ever come across, ' James Miller-Jones, a professor from the Curtin University in Australia and lead author of the study, said in a statement.

"The two are separated by about 20 million kilometers [12 million miles]; close enough that the gravity of the black hole is able to pull the outer layers off the star, with the gas then swirling in towards the black hole in a thin disk-like structure known as an accretion disk", Miller-Jones told Newsweek.

"What's different in V404 Cygni is that we think the disk of material and the black hole are misaligned". As a result of the way black holes normally spin, the matter tends to spray out in the same direction.


Miller-Jones and colleagues observed V404 Cygni using the Very Long Baseline Array (VLBA), a network of 10 radio telescopes spread out across the globe that are owned and operated by the National Science Foundation (NSF).

The black hole itself is rotating and the gravitational pull is so strong, it's actually pulling nearby space and time around with it.

"Typically, radio telescopes produce a single image from several hours of observation, but these jets were changing so fast that in a four-hour image we just saw a blur", she explained. They think material from the innermost rim of the accretion disc is funnelled along the black hole's magnetic field lines, which act as a synchrotron to accelerate the particles before launching them at tremendous velocities.

"It was like trying to take a picture of a waterfall with one-second shutter speed".

The jet blobs are spitting out at very near the speed of light and in a few hours are traversing a distance that is the size of our solar system, said Sivakoff, adding researchers want to find out if this behaviour is special in comparison to other black holes.

Like a black hole isn't mysterious enough, researchers have now found one emitting rapidly-swinging jets. This time though, the astronomers made 103 individual images that were each approximately 70 seconds long, and then combined them to make a movie in order to show the jets' rapid motion.

According to the team, this could have implications for our understanding of other similar extreme events in the universe. The binary star system consists of a normal star in orbit with a black hole.

Our best explanation for such rapid changes is that the jets were being redirected by a wobbling inner accretion flow around a spinning black hole.

They have turned to Einstein's equations of general relativity to predict the world inside a black hole.

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