Spiral light on the edge of the supermassive black hole, M87*, could help understand how these giants consume surrounding matter. Simultaneously, scientists may consequently comprehend how matter escapes the consumption of these cosmic titans.

M87* black hole has a mass equivalent to about 6.5 billion suns and is located approximately 54 million light-years from Earth. It captured public attention notably in 2019 when the image, captured by the Event Horizon Telescope (EHT), provided humanity’s first glimpse of the environment around a black hole.

Polarized Light

Research group behind that historic image modeled how the electric fields of light rotate around the black hole. Polarized light carries information about the magnetic field and particles that are accelerated at speeds close to light around the M87* black hole.

Scientists suggest that these magnetic fields could deprive M87* of matter to swallow. Instead, it would be shot out at the speed of light into space in the form of parallel jets. “Circular polarization is the final signal we were looking for in the early EHT observations of the M87* black hole. It has by far been the most challenging data to analyze” said Andrew Chael (ref.), a co-author of the study (ref.).

“These results confirm the presence of a strong magnetic field permeating the hot gas surrounding the black hole” added Chael. “The unprecedented observations of the EHT are allowing us to answer long-standing questions. How do black holes consume matter and launch jets outside the galaxies that host them?”.

Collaboration between EHT and ALMA

Two years after the release of the M87* black hole image, the EHT collaboration released a second image. The latest photo shows, for the first time, polarized light around a black hole. The 2021 data also revealed the direction of oscillating electric fields, providing the first hint that the magnetic fields around M87* are strong and orderly.

Researchers then took a closer look using the Atacama Large Millimeter/submillimeter Array (ALMA). The 66 antennas in the Chilean desert can peer through dusty cosmic environments, such as black holes, to search for longer-wavelength light.

The collected data show how the electric fields of light twist in a linear direction, further evidence of the magnetic fields glimpsed in 2021. So, EHT scientists, using computer simulation, suggest that these strong magnetic fields repel matter falling toward M87*.

The power of the magnetic fields propels the jets of matter at speeds close to that of light, before the matter passes through the black hole’s event horizon. Researchers continue to analyze the data to find stronger evidence of linear polarization. “The work could still have room for improvement,” said Hugo Messias, a study co-author leading the VLBI team at ALMA.

“This circularly polarized light that has now been detected is very weak. In recent years, the EHT has observed with more stations and increased sensitivity. This means that ongoing analysis will likely provide new insights into the secrets around M87*”.

Stefano Gallotta
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