ALMA Discovers Extremely Intense Magnetic Field Near a Supermassive Black Hole

ALMA has made a startling new discovery. It's detected an extremely powerful magnetic field at the core of a galaxy, close to the event horizon of a supermassive black hole.

Supermassive black holes often have masses that are billions of times that of the sun. They can be found at the hearts of almost all galaxies in the universe. They accrete huge amounts of matter in the form of a surrounding disk and while most of this matter is fed into the black hole, some can escape moments before capture and be lung out into space at close to the speed of light.

Up until now, scientists have only examined weak magnetic fields far from black holes. However, this latest study homes in on signals directly related to a strong magnetic field very close to the event horizon of the supermassive black hole located in a distant galaxy named PKS 1830-211.

The researchers measured the strength of the magnetic field by studying the way in which light was polarized as it moved away from the black hole.

"Polarization is an important property of light and is much used in daily life, for example in sun glasses or 3D glasses at the cinema," said Ivan Marti-Vidal, lead author of the new study, in a news release. "When produced naturally, polarization can be used to measure magnetic fields, since light changes its polarization when it travels through a magnetized medium. In this case, the light that we detected with ALMA had been traveling through material very close to the black hole, a place full of highly magnetized plasma."

The researchers applied a new analysis technique and found that the direction of polarization of the radiation coming from the center of the galaxy had rotated. They found clear signals of polarization rotation that were hundreds of times higher than the highest ever found in the universe.

"Our discovery is a giant leap in terms of observing frequency, thanks to the use of ALMA, and in terms of distance to the black hole where the magnetic field has been probed-of the order of only a few light-days from the event horizon," said Sebastien Muller, co-author of the new study. "These results, and future studies, will help us understand what is really going on in the immediate vicinity of supermassive black holes."

The findings are published in the journal Science.

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