Astronomers have witnessed a black hole spraying jets of plasma into
space like a rotating sprinkler as it ripped apart a star in a feeding
frenzy.
The dramatic display is the first time such wild, rapid motion has been detected in black hole jets, said James Miller-Jones of the International Centre for Radio Astronomy Research (ICRAR) at Curtin University.
Often, as the immense gravity of a black hole pulls gas from a nearby star, some of that material is shot back into space at nearly the speed of light. Usually those jets blaze straight "up" and "down", along the axis on which the black hole spins.
But the jets from black hole V404-Cygni were swinging around, shooting out plasma in different directions, Professor Miller-James and colleagues report today in the journal Nature.
"Our best explanation is that this is actually caused by an effect of Einstein's general relativity, whereby the black hole is spinning and it's pulling space and time around with it," he said.
The movement appears to be triggered by a misalignment between the rotation of the black hole and the disc of material swirling around it. This causes the inner part of the disc to wobble like a spinning top, pulling the jets around with it.
"We think the jets are rotating around the surface of a cone, essentially drawing out a corkscrew-shaped pattern in space as they move outwards," Professor Miller-Jones said.
Historic records also show the system was active in 1938 and 1956.
In 2015, Professor Miller-Jones led a 21-strong team from around the world using the Very Long Baseline Array (VLBA) to observe the feeding frenzy.
With its network of 10 radio telescopes spread across the US, the VLBA was able to home in on V404-Cygni to the scale of our solar system — in a very similar way to how astronomers recently captured the first image of a black hole's event horizon.
However, because this black hole was evolving so fast, the team had to use a special technique to capture it in action.
"Usually when you have one observation you take all the data and use all that data to make a single image, but because we actually saw the jets changing and moving over timescales as short as a few minutes, we had to chop up the observation," Professor Miller-Jones said.
Across a four-hour period, the team ended up with more than 100 snapshots which they then stitched together to make a movie.
"That allowed us to see exactly what was going on," Professor Miller-Jones said.
"It would be like trying to take a picture of a waterfall with a one-second shutter speed. You just couldn't do it."
"The new insights we learn from systems [like V404-Cygni] can be applied to the bigger systems that affect the universe on really large scales," he said.
"The physics occurring on very small scales near the black hole dictates how its energy is channelled outwards into the surrounding galaxy. For supermassive black holes in the centres of galaxies, this can impact regions of space far larger than the host galaxy itself."
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".
"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.
"This lets astrophysicists examine new details of how black holes spin. It's a very exciting time to be in this field."
The dramatic display is the first time such wild, rapid motion has been detected in black hole jets, said James Miller-Jones of the International Centre for Radio Astronomy Research (ICRAR) at Curtin University.
Often, as the immense gravity of a black hole pulls gas from a nearby star, some of that material is shot back into space at nearly the speed of light. Usually those jets blaze straight "up" and "down", along the axis on which the black hole spins.
But the jets from black hole V404-Cygni were swinging around, shooting out plasma in different directions, Professor Miller-James and colleagues report today in the journal Nature.
"Our best explanation is that this is actually caused by an effect of Einstein's general relativity, whereby the black hole is spinning and it's pulling space and time around with it," he said.
The movement appears to be triggered by a misalignment between the rotation of the black hole and the disc of material swirling around it. This causes the inner part of the disc to wobble like a spinning top, pulling the jets around with it.
"We think the jets are rotating around the surface of a cone, essentially drawing out a corkscrew-shaped pattern in space as they move outwards," Professor Miller-Jones said.
Different approach captures black hole in action
An outburst from V404-Cygni, which is 8,000 light years from Earth and nine times the mass of our sun, was first captured in 1989.Historic records also show the system was active in 1938 and 1956.
In 2015, Professor Miller-Jones led a 21-strong team from around the world using the Very Long Baseline Array (VLBA) to observe the feeding frenzy.
With its network of 10 radio telescopes spread across the US, the VLBA was able to home in on V404-Cygni to the scale of our solar system — in a very similar way to how astronomers recently captured the first image of a black hole's event horizon.
However, because this black hole was evolving so fast, the team had to use a special technique to capture it in action.
"Usually when you have one observation you take all the data and use all that data to make a single image, but because we actually saw the jets changing and moving over timescales as short as a few minutes, we had to chop up the observation," Professor Miller-Jones said.
Across a four-hour period, the team ended up with more than 100 snapshots which they then stitched together to make a movie.
"That allowed us to see exactly what was going on," Professor Miller-Jones said.
"It would be like trying to take a picture of a waterfall with a one-second shutter speed. You just couldn't do it."
Phenomenon could affect universe on large scales
V404-Cygni is a lightweight on the scale of black holes, but Professor Miller-Jones said effects seen in this system could happen with any black hole system, including supermassive black holes that lie at the heart of galaxies."The new insights we learn from systems [like V404-Cygni] can be applied to the bigger systems that affect the universe on really large scales," he said.
"The physics occurring on very small scales near the black hole dictates how its energy is channelled outwards into the surrounding galaxy. For supermassive black holes in the centres of galaxies, this can impact regions of space far larger than the host galaxy itself."
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".
"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.
"This lets astrophysicists examine new details of how black holes spin. It's a very exciting time to be in this field."
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