Decades-old mystery of plasma jets solved by 'heartbeat' of black hole

Astronomers have resolved the decades-old mystery of plasma jets by taking the ''heartbeat'' of a black hole.

The research, published in Nature Astronomy, was led by Mariano Méndez from the University of Groningen in the Netherlands.

There are three categories of black holes. The smallest, like 'the Unicorn,' are so-called stellar mass black holes formed by the gravitational collapse of a single star. There are gargantuan 'supermassive' black holes like the one at our galaxy's center, 26,000 light years from Earth, which is four million times the sun's mass. A few intermediate-mass black holes also have been found with masses somewhere in between.

Just as the blood in a human heart cannot be in the atrium and in ventricles at the same time, a black hole also appears to first collect material and heat it up in a so-called corona, only then to spit it out in jets.

"It sounds logical, but there has been a debate for twenty years about whether the corona and the jet were simply the same thing. Now we see that they arise one after the other and that the jet follows from the corona," says Méndez.

"It was quite a challenge to demonstrate this sequential nature. We had to compare data of years with that of seconds, and of very high energies with very low ones."

The black hole GRS 1915+105 is not an isolated black hole, but a double system consisting of a black hole and a normal star that circle around each other. This double system lies in our Milky Way at about 36,000 light years from us in the direction of the constellation Aquila. The black hole weighs about as much as twelve times our Sun, making it one of the heaviest known stellar black holes.

"It was quite a challenge to demonstrate this sequential nature," Méndez said. "We had to compare data of years with that of seconds, and of very high energies with very low ones."

Now that the researchers have proven the sequence, there are still some unanswered questions. For example, the X-ray radiation that the telescopes collect from the corona contains more energy than can be explained by the temperature of the corona alone. The researchers suspect that a magnetic field provides extra energy.

This magnetic field and the accompanying energy could also explain why jets are formed. If the magnetic field is chaotic, the corona heats up. If the magnetic field then becomes less chaotic, material can escape via the field lines into a jet.

The researchers suggest that the principle they demonstrated may also apply to heavier black holes, for example to the supermassive black hole at the centre of our Galaxy.

(With inputs from agencies)