{"id":9389,"date":"2019-04-29T05:00:24","date_gmt":"2019-04-29T15:00:24","guid":{"rendered":"http:\/\/www.eaobservatory.org\/jcmt\/?p=9389"},"modified":"2019-04-30T13:47:50","modified_gmt":"2019-04-30T23:47:50","slug":"9389","status":"publish","type":"post","link":"https:\/\/www.eaobservatory.org\/jcmt\/2019\/04\/9389\/","title":{"rendered":"Spinning Black Hole Sprays Light-speed Plasma Clouds into Space"},"content":{"rendered":"

An international team of astronomers, including Dr Alex Tetarenko, a researcher working at the East Asian Observatory in Hilo, Hawai\u2019i, have discovered rapidly swinging jets coming from a black hole within our own Galaxy the Milky Way, almost 8,000 light-years from Earth. This black hole is much closer to us than <\/span>P<\/span>\u014d<\/span>wehi, a <\/span>black hole recently imaged with the Event Horizon Telescope, located around 56 million light-years away from Earth in another Galaxy.<\/span><\/em><\/i><\/p>\n

Published today in the journal <\/span>Nature<\/span><\/i>, the research shows jets from V404 Cygni\u2019s black hole behaving in a way never seen before on such short timescales.<\/span><\/i><\/p>\n

The rapidly spinning black hole in V404 Cygni was observed to eject high-speed clouds of plasma, known as jets, travelling at close to the speed of light. These jets appeared to also be rapidly rotating, with multiple clouds of material ejected just minutes apart.<\/span><\/i><\/p>\n

Lead author Associate Professor James Miller-Jones, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), said black holes are some of the most extreme objects in the Universe.<\/i><\/p>\n

\u201cThis is one of the most extraordinary black hole systems I\u2019ve ever come across,\u201d Associate Professor Miller-Jones said. <\/i>\u201cLike many black holes, it\u2019s feeding on a nearby star, pulling gas away from the star and forming a disk of material that encircles the black hole and spirals towards it under gravity\u201d.<\/p>\n

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An artist’s impression of the binary system that includes the black hole V404 Cygni and a sun-like star that orbit one another. Credit: ICRAR.<\/p><\/div>\n

\u201cWhat\u2019s different in V404 Cygni is that we think the disk of material and the black hole are misaligned. This appears to be causing the inner part of the disk to wobble like a spinning top and fire jets out in different directions as it changes orientation.\u201d<\/p>\n

V404 Cygni, located in the constellation of Cygnus, was first identified as a black hole in 1989 when it released a big outburst of jets and material.<\/span><\/i><\/p>\n

Astronomers looking at archival photographic plates then found previous outbursts in observations from 1938 and 1956. <\/span><\/i><\/p>\n

Associate Professor Miller-Jones said that when V404 Cygni experienced another very bright outburst in 2015, lasting for two weeks, telescopes around the world tuned in to study what was going on.<\/span><\/i><\/p>\n

\u201cEverybody jumped on the outburst with whatever telescopes they could throw at it. So we have this amazing observational coverage\u201d he said.<\/span><\/i><\/p>\n

When Associate Professor Miller-Jones and his team studied the black hole, they saw its jets behaving in a way never seen before.<\/span><\/i><\/p>\n

Where jets are usually thought to shoot straight out from the poles of black holes, these jets were shooting out in different directions at different times.<\/span><\/p>\n

And they were changing direction very quickly\u2014over no more than a couple of hours.<\/span><\/i><\/p>\n

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An artist’s impression of the inner parts of the accretion disk around the black hole V404 Cygni. Credit: ICRAR.<\/p><\/div>\n

Associate Professor Miller-Jones said the change in the movement of the jets was because of the accretion disk\u2014the rotating disk of matter around a black hole.<\/span><\/i><\/p>\n

He said V404 Cygni\u2019s accretion disk is 10 million kilometres wide, 7 times the diameter of the Sun, and the inner few thousand kilometres was puffed up and wobbling during the bright outburst.<\/span><\/i><\/p>\n

\u201cThe inner part of the accretion disk was precessing and effectively pulling the jets around with it. You can think of it like the wobble of a spinning top as it slows down\u2014only in this case, the wobble is caused by Einstein\u2019s theory of general relativity.\u201d Associate Professor Miller-Jones said.<\/span><\/i><\/p>\n

The research used observations from the Very Long Baseline Array, a continent-sized radio telescope made up of 10 dishes across the United States, from the Virgin Islands in the Caribbean to Maunakea, Hawai\u2019i.<\/span><\/i><\/p>\n

Co-author Alex Tetarenko\u2014an East Asian Observatory Fellow working in Hilo Hawai`i, and a recent PhD graduate from the University of Alberta \u2014said the speed the jets were changing direction meant the scientists had to use a very different approach to most radio observations.<\/span><\/i><\/p>\n

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Dr Alex Tetarenko outside of the James Clerk Maxwell Telescope Office in Hilo, Hawai\u02bbi. Credit: Alyssa Clark<\/p><\/div>\n

\u201cTypically, 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. It was like trying to take a picture of a waterfall with a one-second long exposure\u201d Dr. Tetarenko said.<\/span><\/i><\/p>\n

Observations taken by Dr. Tetarenko and her team with two more telescopes on Maunakea, Hawai`i, the James Clerk Maxwell Telescope (JCMT) and the Sub-millimeter Array (SMA), also hinted at a rapidly evolving jet. Previously published in the journal Monthly Notices of the Royal Astronomical Society<\/em>,<\/a><\/span>\u00a0these observations tracking the brightness of the jet over time, revealed extreme flaring events that coincided with the directly imaged jet ejection events.<\/span><\/i><\/p>\n

\u201cThe incredible changes in brightness we saw in this JCMT and SMA data, and the model we designed to explain these changes, provided key information needed to develop our imaging method for this paper\u201d she said.<\/span><\/i><\/p>\n

To directly image these rapidly changing jets, the researchers produced 103 individual images, each about 70 seconds long. Miller-Jones and Tetarenko then led the efforts to combine those images into a continuous video\u2014a difficult task, as each image required its own careful analysis.<\/span><\/i><\/p>\n

\u201cThe result has been well worth the effort, illustrating this unique and unusual black hole behaviour\u201d Dr. Tetarenko said.<\/span><\/i><\/p>\n

\u201cWe were gobsmacked by what we saw in this system\u2014it was completely unexpected,\u201d said study co-author Gregory Sivakoff, a University of Alberta astrophysicist. \u00a0\u201cFinding this astronomical first has deepened our understanding of how matter behaves near black holes\u201d.<\/span><\/i><\/p>\n

Study co-author Dr Gemma Anderson, who is also based at ICRAR\u2019s Curtin University node, said the wobble of the inner accretion disk could happen in other extreme events in the Universe too.<\/span><\/i><\/p>\n

\u201cAnytime you get a misalignment between the spin of black hole and the material falling in, you would expect to see this when a black hole starts feeding very rapidly,\u201d Dr Anderson said.<\/span><\/i><\/p>\n

\u201cThat could include a whole bunch of other bright, explosive events in the Universe, such as supermassive black holes feeding very quickly or tidal disruption events, when a black hole shreds a star.\u201d<\/span><\/p>\n