The supermassive black hole at the centre of galaxy M87 has stunned astronomers by showing an unexpected flip in its polarisation pattern. The discovery, made with the Event Horizon Telescope (EHT), suggests the region around the black hole is far more turbulent than previously thought.
A cosmic flip
By comparing EHT data from 2017, 2018 and 2021, scientists found the polarisation, the orientation of light waves that traces magnetic fields, switched direction.
In 2017, the fields appeared to spiral one way. By 2018, the pattern looked steadier. In 2021, the orientation had flipped completely, spiralling in the opposite direction.
Such changes may result from the black hole’s own magnetic structure, as well as matter along the way that twists the light before it reaches Earth.
“What’s remarkable is that while the ring size has remained consistent over the years—confirming the black hole’s shadow predicted by Einstein’s theory—the polarization pattern changes significantly,” says Paul Tiede of the Center for Astrophysics | Harvard & Smithsonian. “This tells us that the magnetized plasma swirling near the event horizon is far from static; it’s dynamic and complex, pushing our theoretical models to the limit.”
Why it matters
M87* is more than six billion times the mass of the Sun and lies 55 million light-years away. It powers a colossal relativistic jet, a stream of high-energy particles fired into space at nearly the speed of light.
“Jets like the one in M87 play a key role in shaping the evolution of their host galaxies. By regulating star formation and distributing energy across vast distances, they affect the life cycle of matter on cosmic scales,” explains Eduardo Ros from the Max Planck Institute for Radio Astronomy.
A clearer view of the jet base
The 2021 observing run added two new EHT stations, Kitt Peak in Arizona and NOEMA in France, giving the network sharper vision. Performance upgrades at the Greenland Telescope and James Clerk Maxwell Telescope also boosted sensitivity.
These improvements allowed the team to constrain, for the first time with the EHT, the emission direction of the base of M87*’s jet.
“The improved calibration has led to a remarkable boost in data quality and array performance, with new short baselines – between NOEMA and the IRAM 30m telescopes, and between Kitt Peak and SMT, providing the first constraints on the faint jet base emission,” says Sebastiano von Fellenberg, formerly at MPIfR and now Humboldt-Lynen Fellow at CITA (University of Toronto). “This leap in sensitivity also enhances our ability to detect subtle polarization signals.”
What comes next
“These multi-year observations reveal just how turbulent and dynamic the environment is close to the event horizon. The next step will be to capture the variations of ring and jet with more frequent observations, ideally in a movie which would address the still poorly understood kinematics on event horizon scales,” says Thomas Krichbaum of MPIfR.
“These latest results illustrate the remarkable dynamism around a supermassive black hole. The evolving polarization patterns and the first insights into the jet base bring us closer to understanding the interplay between magnetic fields, accretion, and jet launching,” adds J. Anton Zensus, founding chair of the EHT collaboration. “They also demonstrate the value of long-term international collaboration and sustained technical innovation in radio astronomy, opening entirely new windows onto the universe.”
Published by Kerry Harrison
Kerry’s been writing professionally for over 14 years, after graduating with a First Class Honours Degree in Multimedia Journalism from Canterbury Christ Church University. She joined Orbital Today in 2022. She covers everything from UK launch updates to how the wider space ecosystem is evolving. She enjoys digging into the detail and explaining complex topics in a way that feels straightforward. Before writing about space, Kerry spent years working with cybersecurity companies. She’s written a lot about threat intelligence, data protection, and how cyber and space are increasingly overlapping, whether that’s satellite security or national defence. With a strong background in tech writing, she’s used to making tricky, technical subjects more approachable. That mix of innovation, complexity, and real-world impact is what keeps her interested in the space sector.