Scientists capture image of black hole emitting high-energy jets
An image of a huge, powerful jet of plasma powered by a supermassive black hole has been captured by researchers in unprecedented detail.
The team say the bright blob on the left of the image is thought to be the disc of gas and dust swirling around the black hole, with the jet of plasma depicted by a stream of less intense red features apparently emanating from it.
Experts say the jet is part a structure known as a blazar. These are formed from quasars – supermassive black holes which are actively sucking in material – that wind up magnetic fields as they spin, resulting in material from around the black hole being shot out in two jets, one of which points towards the Earth.
“A lot of that matter [around the black hole] is fated just to cross the event horizon and never return, but some of it can be launched along those powerful magnetic field lines which thread the black hole, and that is what the jet is,” said Dr Ziri Younsi of University College London, a co-author of the study.
“Black holes don’t just swallow up a lot of matter, they spit a lot of it out too because they are highly magnetised and spinning so rapidly,” he added.
Crucially, the team say, the image is the highest resolution yet of a jet around a supermassive black hole, meaning the researchers can for the first time investigate what is happening near the base of the jet. Indeed a close-up image shows a blob near the black hole that appears to be slightly off the axis of the rest of the jet.
“It is offset by a good few degrees,” said Younsi.
That, he added, means there may be a sort of “kink” at the base of the jet, or material that is being twisted around the jet. Alternatively, the blobs could be part of the edge of the disc of gas and dust that surrounds and feeds the black hole.
But, Younsi added, questions remain, including what exactly the plasma of the jet is composed of, and exactly how the jet couples with the black hole.
The image, published in the journal Astronomy & Astrophysics, was captured by the Event Horizon Telescope – a huge research effort involving a network of eight radio telescopes, and a large team of researchers, around the world.
The team say the black hole is part of a quasar called 3C 279, and is 200 times larger than the black hole at the centre of the Milky Way. The quasar, they add, lies in a galaxy 5bn light years away in the constellation Virgo.
“It is actually very far away,” said Younsi. “Normally we wouldn’t be able to see anything, because the light would just be so red-shifted by the time it reaches us.
“But because this jet is fired almost directly towards us, all of that radiation is boosted and it appears a lot brighter than it really is and so we are able to detect it.”
The direction of the jet, pointing towards Earth, also explains another curiosity – why the jet appears to be travelling 15-20 times faster than the speed of light.
“It is a projection effect,” said Younsi, noting that the is jet actually travelling about 0.995 times the speed of light.
The new work is not the first stunning image from the Event Horizon Telescope endeavour: last year the team released the first image of a black hole, revealing a glowing halo of gas and dust.
But Younsi said the new images were even more exciting to physicists. “It is the first time we really start to see the connection of the jet with the black hole and the accretion disc [of gas and dust,]” he said. “It actually allows us to start answering questions about how black holes power jets, how black holes feed, how they grow.”
That, he added, is important as not all galaxies have a black hole with large-scale jets – including our own Milky Way. “One of the big questions is why – why don’t we have a big jet like a lot of other galaxies?” said Younsi.
Younsi said the new image was a sign of things to come.
“This is just very preliminary work, this is the beginning really,” he said.
