Here’s why some supermassive black holes burn so badly

For the first time, astronomers have observed how some supermassive black holes shoot jets of high-energy particles into space — and the process is shocking.

Shock waves propagate along the jet of one of these blazars Twisting magnetic fields that accelerate the escaping particles to nearly the speed of light, astronomers reported on November 23 at nature. Studying such intense acceleration can help investigate fundamental physics questions that cannot be studied in any other way.

Blazars are active black holes Shooting jets of high-energy particles toward Earthmaking them appear as bright spots from millions or even billions of light-years away (SN: 7/14/15). Astronomers knew that the jets’ top speeds and narrow vertical beams had something to do with the shape of the magnetic fields around black holes, but the details were fuzzy.

Enter the Imaging X-Ray Polarimetry Explorer, or IXPE, an orbiting telescope launched in December 2021. Its mission is to measure X-ray polarization, or how X-ray light is directed as it travels through space. While Blazar’s notes were prior to Polarized radio waves and optical light Examined parts of the jets days to years after they accelerated, the polarized X-rays could see into the active nucleus of the blazar (SN: 3/24/21).

“In X-rays, you’re really looking at the heart of particle acceleration,” says astrophysicist Yannis Liodakis of the University of Turku in Finland. “You’re really looking at the area where it all happens.”

In March 2022, IPXE looked at a particularly bright blazer called Markarian 501, located about 450 million light-years from Earth.

Liodakis and his colleagues had two main ideas about how magnetic fields could accelerate Markarian 501’s jet. The particles can be boosted by magnetic reconnection, in which magnetic field lines break, reform and connect with other nearby lines. Same process Plasma accelerates on the sun (SN: 11/14/19). If this is the particle acceleration driver, then the polarization of light must be the same along the plane in all wavelengths, from radio waves to X-rays.

Another option is a shock wave that shoots particles down an aircraft. At the shock site, the magnetic fields suddenly switch from disordered to orderly. This switch can send distant particles, such as water through the nozzle of a hose. When the particles leave the impact site, the disturbance should pick up again. If the shock was responsible for the acceleration, short-wavelength X-rays must be more polarized than longer-wavelength optical and radio light, as measured by other telescopes.

Illustration of the IXPE spacecraft observing polarized X-rays from Blazar and its jets
The observed IXPE spacecraft (pictured) polarized X-rays come from Blazar and its jets. The inset shows how particles in the jet collided with a shock wave (white) and boosted to extreme speeds, emitting high-energy X-ray light. As they lose energy, the particles emit low-energy light in the visible, infrared, and radio wavelengths (purple and blue), and the plane becomes more turbulent.Pablo Garcia/MSFC/NASA

That’s exactly what the researchers saw, Lioudakis says. “We got a clear result,” he says, preferring the shock wave interpretation.

There is still work to be done to work out the details of how the particles flow, says astrophysicist James Webb of Florida International University in Miami. First, it is not clear what might result in trauma. But, he says, “this is a step in the right direction.” “It’s like opening a new window and looking at the new thing, and now we’re seeing things we haven’t seen before. It’s very exciting.”

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