A supermassive black hole’s strong magnetic fields are revealed in new light

The Event Horizon Telescope (EHT) collaboration has published new results that describe for the first time how light from the edge of the M87* supermassive black hole is enveloped as it escapes the black hole’s intense gravity, known as circular polarization. The way the light’s electric field prefers to spin clockwise or counter-clockwise carries information about the magnetic field and the types of high-energy particles around the black hole.

A new paper published today The Astrophysical Journal Letterssupports earlier EHT findings that the magnetic field near the M87* black hole is strong enough to occasionally prevent the black hole from swallowing nearby matter.

The Atacama Large Millimeter/Submillimeter Array (ALMA) is the world’s most powerful millimeter/submillimeter telescope and the EHT’s main instrument. The spiral light behind this research is actually composed of low-frequency radio wave light that is not visible to the human eye or an optical telescope, but can be observed by multiple radio telescopes, including ALMA, working together at the EHT. .

“Circular polarization is the final signal we looked for in the first observations of the M87 black hole, and it was the most difficult to analyze,” said Andrew Chell, an associate researcher at Princeton University’s Gravity Initiative, who coordinated the study. the project.

“These new results give us confidence that our picture of a strong magnetic field penetrating the hot gas surrounding the black hole is correct. The unprecedented EHT observations allow us to answer long-standing questions about how black holes consume matter and emit jets. beyond their host galaxies.”

In 2019, the EHT released its first image of a ring of hot plasma near the event horizon of M87*. In 2021, EHT scientists published an image that showed the directions of electric fields oscillating across the image. This result, known as linear polarization, was the first indication that the magnetic fields near a black hole are ordered and strong. New circular polarization measurements showing how light’s electric fields rotate around a linear direction from the 2021 analysis provide clearer evidence for these strong magnetic fields.

ALMA provided both the data and calibration for these results and served as the bulk reference antenna for the EHT. Without the much higher sensitivity of ALMA as a reference antenna, circular polarization could not have been detected.