It took another two years for researchers to produce the polarized images released on Wednesday.

Jets and lobes of radio, X-ray and other forms of energy extend more than 100,000 light-years from the black hole in M87. Much of this radiation comes from energetic electrical particles spiraling around in magnetic fields.

The newly processed image allows the astronomers to trace these fields back to their origins, in a hot, chaotic ring of electrified gas, or plasma, about 30 billion miles across — four times as wide as the orbit of Pluto. That achievement is made possible because the light from the disk is partly polarized, vibrating more in one direction than in others.

“The direction and intensity of the polarization in the image tells us about the magnetic fields near the event horizon of the black hole,” said Andrew Chael, an astrophysicist at Princeton University who is part of the Event Horizon team.

Astronomers have debated for years whether the magnetic fields surrounding so-called low-luminosity black holes like M87 were weak and turbulent or “strong” and coherent. In this case, Dr. Chael said, the magnetic fields are strong enough to disrupt the fall of the gas and transfer energy from the spinning black hole to the jet.

“The E.H.T. images also provide hints that the bright jet in M87 is actually powered from the rotational energy of the black hole, which twists the magnetic fields as it rotates,” said Michael Johnson another Event Horizon member from the Harvard-Smithsonian Center for Astrophysics.

As a result, Dr. Doeleman said, “This gives the emitted radio waves the azimuthal twist” observed in the curving pattern of the new, polarized images. He noted that azimuthal twist would be a “fine name for a cocktail.”

A byproduct of the work, Dr. Doeleman said, was that the astronomers were able to estimate the rate at which the black hole is feeding on its environment. Apparently it isn’t terribly hungry; the black hole is eating “a paltry” one-thousandth of the mass of the sun per year.

“Yet it’s enough to launch powerful jets that stretch for thousands of light years, and it’s radiant enough for us to capture it with the E.H.T.,” he said.

Dr. Doeleman is already laying the groundwork for what he calls the “next generation” Event Horizon Telescope, which will produce movies of this magnetic propulsion structure in action.

“This is really the next big question,” Dr. Doeleman said. “How do magnetic fields extract energy from a spinning black hole? We know it happens, but we don’t know how it works. To solve that, we will need to create the first black hole cinema.”

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