Right here’s why some supermassive black holes blaze so brightly


For the primary time, astronomers have noticed how sure supermassive black holes launch jets of high-energy particles into house — 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 might help probe basic physics questions that may’t be studied every other means.

Blazars are energetic black holes that shoot jets of high-energy particles towards Earth, making them seem as shiny spots from tens of millions 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 mild is oriented because it travels by means of house. Whereas earlier blazar observations of polarized radio waves and optical mild 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 trying on the coronary heart of the particle acceleration,” says astrophysicist Yannis Liodakis of the College of Turku in Finland. “You’re actually trying on the area the place every thing occurs.”

In March 2022, IPXE checked out an particularly shiny blazar referred to as Markarian 501, positioned about 450 million light-years from Earth.

Liodakis and colleagues had two principal concepts for a way magnetic fields would possibly speed up Markarian 501’s jet. Particles might be boosted by magnetic reconnection, the place magnetic discipline traces break, reform and join with different close by traces. The identical course of accelerates plasma on the solar (SN: 11/14/19). If that was the particle acceleration engine, the polarization of sunshine ought to be the identical alongside the jet in all wavelengths, from radio waves to X-rays.

Another choice is a shock wave capturing particles down the jet. On the web site of the shock, the magnetic fields abruptly swap from turbulent to ordered. That swap might ship particles zooming away, like water by means of the nozzle of a hose. Because the particles depart the shock web site, turbulence ought to take over once more. If a shock was answerable for the acceleration, quick wavelength X-rays ought to be extra polarized than longer wavelength optical and radio mild, as measured by different telescopes.

The IXPE spacecraft (illustrated) noticed polarized X-rays come from a blazar and its jet. The inset illustrates how particles within the jet hit a shock wave (white) and get boosted to excessive speeds, emitting high-energy X-ray mild. As they lose vitality, the particles emit decrease vitality mild in seen, infrared and radio wavelengths (purple and blue), and the jet turns into extra turbulent.Pablo Garcia/MSFC/NASA

That’s precisely what the researchers noticed, Liodakis says. “We bought a transparent consequence,” he says, that favors the shock wave rationalization.

There’s nonetheless work to do to determine the small print of how the particles movement, says astrophysicist James Webb of Florida Worldwide College in Miami. For one, it’s not clear what would produce the shock. However “it is a step in the best path,” he says. “It’s like opening a brand new window and searching on the object freshly, and we now see issues we hadn’t seen earlier than. It’s very thrilling.”


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