At the heart of a quasar, a supermassive black hole, millions or even billions of times the mass of our sun, devours matter from a swirling, ultra-hot disk. This charged matter, called plasma, is drawn towards the black hole’s gravity, but not all of it gets swallowed. Instead, some of the plasma is expelled in powerful jets, collimated by the black hole’s magnetic field, before it reaches the point of no return, known as the event horizon. These jets can stretch thousands of light-years into space.
However, the physics behind the formation of these jets at their base has remained a mystery. Now, researchers at the Princeton Plasma Physics Laboratory (PPPL) in New Jersey have found a possible answer. They modified a plasma-measuring technique called proton radiography to create a high-energy density plasma using laser beams. This plasma then interacted with a magnetic field, allowing scientists to observe the process in detail.
The experiment involved firing a laser beam at a plastic target, creating a high-energy density plasma. Then, powerful lasers were used to initiate nuclear fusion in a fuel capsule filled with deuterium and helium-3. This fusion reaction released bursts of protons and X-rays. These particles then passed through a nickel mesh, acting like a colander, separating the protons into beams that measured the expanding plasma’s interaction with the background magnetic field. The X-rays, passing cleanly through the mesh, provided an undistorted image of the plasma, allowing scientists to compare it with the proton beam measurements.
The researchers observed the magnetic field bending outward under pressure from the expanding plasma, creating a phenomenon known as magneto-Rayleigh Taylor instability. This instability resulted in swirling and mushroom-shaped formations in the magnetic field. As the plasma energy decreased, the magnetic field lines snapped back, compressing the plasma into a straight, narrow column – remarkably similar to a quasar’s relativistic jet.
This discovery provides strong evidence that magneto-Rayleigh Taylor instability is the key driver behind the formation of quasar jets. The intense conditions in the black hole’s accretion disk cause the plasma to push against the tightly packed magnetic field lines, which then snap back, propelling the plasma into a narrow jet. This finding could be a significant missing piece in our understanding of how active black holes operate.
“Now that we have measured these instabilities very accurately, we have the information we need to improve our models and potentially simulate and understand astrophysical jets to a higher degree than before,” said Sophia Malko, a researcher at PPPL. “It’s interesting that humans can make something in a laboratory that usually exists in space.”
The findings were published on June 27 in the journal Physical Review Research, marking a significant step forward in our understanding of the enigmatic phenomena surrounding active black holes.
