Scientists make lab-grown black hole jets

An experiment using beams of protons to probe how plasma and magnetic fields interact may have just solved the mystery of how quasars and other active supermassive black holes unleash their relativistic jets.

Let's picture the scene at the heart of a quasar. A supermassive black hole, perhaps hundreds of millions — or even billions — of times the mass of our sun, is ravenously devouring matter that is streaming into its maw from a spiraling, ultra-hot disk. That charged matter is called plasma, and it gets gravitationally drawn into the black hole's surroundings — however, not all of the plasma, which is made from ionized, or electrified, atoms shorn of electrons, is swallowed by the black hole. Indeed, the black hole bites off more than it can chew, and some of the plasma is spat out in jets collimated by the black hole's powerful magnetic field before that plasma gets anywhere near the event horizon, which is basically the point of no return.

These jets can stretch thousands of light-years into space. Yet, explaining the physics that takes place at the base of the jet, where they're formed, has eluded scientists.

The answer may have come from researchers at the Princeton Plasma Physics Laboratory (PPPL) in New Jersey, who were able to devise a modification to a plasma-measuring technique called proton radiography.

In their experiment, the researchers first created a high-energy density plasma by firing a pulsed, 20-joule laser beam at a plastic target. Then, they used powerful lasers to instigate nuclear fusion in a fuel capsule filled with deuterium and helium-3. The fusion reactions released bursts of protons and X-rays.

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These protons and X-rays then passed through a nickel mesh filled with tiny holes. Think of the mesh as like a colander for straining pasta; it strains the protons into many discrete beams that then can measure how the expanding plasma plume interacts with a background magnetic field. Because the protons are charged, they'll follow the magnetic field lines as they are buffeted by the plasma. The X-ray burst acts as a check — because the X-rays pass cleanly through the mesh and the magnetic field, they provide an undistorted image of the plasma to compare to the proton beam measurements.