New discoveries

ALMA helps discover strange sideways structure in distant black hole jet

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Astronomers have obtained the sharpest image ever of the powerful jet of material from a giant
black hole, and they made a surprising discovery.
Black holes are regions in space with so much gravity that they gobble up everything in their
neighborhood. Almost all of the gas is falling into the black hole, but a small amount of material is
launched into space, in two opposite directions. In some cases, one of these jets is pointing almost in our direction.
ALMA has now teamed up with other millimeter telescopes around the world to take a close look at one of the jets of a very distant black hole. By combining the power of many telescopes, astronomers could see much more detail than before. As a result, they were able to look close to the ‘launching point’ of the jet – very close to the black hole itself.
The gas in the jet is moving extremely fast, almost at the speed of light. The jet is also very narrow, just like the powerful jet of water from a firehose. The new observations reveal bright clumps of gas in the jet, as if the pump of the cosmic fire truck is sputtering a little bit. Similar structures had been seen before, albeit in less detail.
But the astronomers also detected something weird. Very close to the launch point, they discovered an elongated structure at right angles to the jet. The shape of this structure also changed in the course of a few days. It’s as if some water from the firehose is leaking sideways. Right now, no one has a good explanation for the perpendicular structure. Future observations will hopefully reveal even more detail. Eventually, astronomers want to learn more about the formation of the jets – they are probably produced by strong magnetic fields, but no one knows how.

What?

In April 2017, a worldwide network of millimeter telescopes, including ALMA, studied a number of distant black holes in the universe. One of them was in the core of the glaxy M87, at a distance of 55 million light-years. The telescope network (also known as the Event Horizon Telescope) obtained a detailed image of this massive object – the first-ever photo of a black hole. But the Event Horizon Telescope also studied a less massive black hole much farther away. This black hole sits in the core of a galaxy known as 3C279. Its distance is a whopping 5 bilion light-years. The black hole itself is about a billion times more massive than our Sun – a true giant! Thanks to the ultra-sharp vision of the Event Horizon Telescope, astronomers could discern details in the jet of this black hole as small as one light-year across –comparable to seeing a flea from a distance of 10,000 kilometers.

Who?

The observations of the black hole in 3C279 were carried out simultaneously by no less than eight large millimeter observatories around the world. ALMA, with its 66 separate radio dishes, was one of them. Other telescopes were located in Europe, the United States, and at the South Pole. The network is known as the Event Horizon Telescope. Many dozens of astronomers from all over the world worked together to turn the project into a success. The observing campaign of 3C279 was led by Jae-Young Kim from the Max Planck Institute for Radio Astronomy in Bonn (Germany). The results were published in the European journal Astronomy & Astrophysics.

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