“The fact that the polarization pattern reversed between 2017 and 2021 was completely unexpected,” said Jongho Park, astronomer at Kyunghee University and project collaborator. “This challenges our models and shows that there is still much we don’t understand near the event horizon.”
The Department of Astronomy at USP’s Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG) formally joined the research in 2022 with the arrival of professor Ciriaco Goddi, who has been part of the project since its inception in 2014. Professor Goddi led the group responsible for data calibration within the EHT. He also worked at the Atacama Large Millimeter Array (Alma), a cornerstone of the planetary observatory and the world’s largest and most powerful radio telescope, located 5,000 meters above sea level in the Atacama Desert, Chile.
At IAG, professor Goddi supervises PhD student Douglas Carlos in the investigation of M87’s polarization. “Alma’s observations, conducted in coordination with the EHT, allow us to study magnetic fields on spatial scales much larger than the black hole’s ring. This is crucial for understanding the black hole’s relativistic jet – a narrow beam of energetic particles launched at nearly the speed of light,” Carlos explained. “By combining multi-year observations from Alma and the EHT, we can track the joint evolution of the black hole and its jet, providing essential information for jet evolution models.”
The EHT’s 2021 observations included two new telescopes, Kitt Peak in Arizona, USA, and- Noema in France, which expanded the network’s sensitivity and image clarity. This allowed scientists to determine, for the first time within the EHT, the direction of emission at the base of M87*’s relativistic jet. Improvements to the Greenland and James Clerk Maxwell telescopes in Hawaii also helped enhance data quality in 2021.
“Improved calibration resulted in a clear gain in data quality and organization, enabling the identification of the first features at the jet’s base, where higher sensitivity is required,” said Sebastiano von Fellenberg, postdoctoral researcher at the Canadian Institute for Theoretical Astrophysics (CITA) and the Max Planck Institute for Radio Astronomy (MPIfR), responsible for the project’s calibration. “This technological leap also increases our ability to detect subtle polarization signals.”
