For the primary time, astronomers have noticed how sure supermassive black holes launch jets of high-energy particles into area — and the method is stunning.
Shock waves propagating alongside the jet of 1 such blazar contort magnetic fields that speed up escaping particles to almost the velocity of sunshine, astronomers report November 23 in Nature. Finding out such excessive acceleration can assist probe elementary physics questions that may’t be studied every other manner.
Blazars are energetic black holes that shoot jets of high-energy particles towards Earth, making them seem as brilliant spots from hundreds of thousands and even billions of light-years away (SN: 7/14/15). Astronomers knew that the jets’ excessive speeds and tight columnated beams had one thing to do with the form of magnetic fields round black holes, however the particulars have been 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 gentle is oriented because it travels by area. Whereas earlier blazar observations of polarized radio waves and optical gentle probed elements of jets days to years after they’d been accelerated, polarized X-rays can see right into a blazar’s energetic core (SN: 3/24/21).
“In X-rays, you’re actually wanting on the coronary heart of the particle acceleration,” says astrophysicist Yannis Liodakis of the College of Turku in Finland. “You’re actually wanting on the area the place all the things occurs.”
In March 2022, IPXE checked out an particularly brilliant blazar referred to as Markarian 501, positioned about 450 million light-years from Earth.
Liodakis and colleagues had two fundamental concepts for a way magnetic fields would possibly speed up Markarian 501’s jet. Particles may very well be boosted by magnetic reconnection, the place magnetic area strains break, reform and join with different close by strains. The identical course of accelerates plasma on the solar (SN: 11/14/19). If that was the particle acceleration engine, the polarization of sunshine must be the identical alongside the jet in all wavelengths, from radio waves to X-rays.
Another choice is a shock wave taking pictures particles down the jet. On the website of the shock, the magnetic fields all of a sudden swap from turbulent to ordered. That swap might ship particles zooming away, like water by the nozzle of a hose. Because the particles depart the shock website, turbulence ought to take over once more. If a shock was liable for the acceleration, quick wavelength X-rays must be extra polarized than longer wavelength optical and radio gentle, as measured by different telescopes.
That’s precisely what the researchers noticed, Liodakis says. “We received a transparent end result,” he says, that favors the shock wave clarification.
There’s nonetheless work to do to determine the small print of how the particles circulate, says astrophysicist James Webb of Florida Worldwide College in Miami. For one, it’s not clear what would produce the shock. However “this can be a step in the fitting route,” he says. “It’s like opening a brand new window and looking out on the object freshly, and we now see issues we hadn’t seen earlier than. It’s very thrilling.”
