M87* One Year Later: Catching the Black Hole’s Turbulent Accretion Flow

M87* One Year Later: Catching the Black Hole’s Turbulent Accretion Flow

The gas sucked in by the iconic supermassive black hole in the galaxy M87 appears to be moving against the black hole’s direction of rotation. This is shown by new computer simulations from the Event Horizon Telescope collaboration, which includes researchers from Radboud University.

Using observations from 2017 and 2018, the Event Horizon Telescope (EHT) Collaboration has deepened our understanding of the supermassive black hole at the center of Messier 87 (M87*). This study opens a new window into multi-year analysis at horizon scales by leveraging a new simulation image library with more than 120,000 additional images compared to the last one. The team confirmed that M87*’s black hole rotational axis points away from Earth and demonstrated that turbulence within the accretion disk - rotating gas around the black hole - plays an important role in explaining the observed shift in the ring’s brightness peak compared to 2017. The findings, published in Astronomy & Astrophysics , mark a major step forward in unraveling the complex dynamics of black hole environments.

Six years after the historic release of the first-ever image of a black hole, the Event Horizon Telescope (EHT) Collaboration unveils a new analysis of the supermassive black hole at the heart of the galaxy M87, known as M87*. This analysis combines observations made in 2017 and 2018, and reveals new insights into the structure and dynamics of plasma near the event horizon.

Leap forward

This research represents a significant leap forward in our understanding of the extreme processes governing black holes and their environments, providing fresh theoretical insights into some of the universe’s most mysterious phenomena. "The black hole accretion environment is turbulent and dynamic. Since we can treat the 2017 and 2018 observations as independent measurements, we can constrain the black hole’s surroundings with a new perspective," says Hung-Yi Pu, assistant professor at National Taiwan Normal University. "This work highlights the transformative potential of observing the black hole environment evolving in time."

The 2018 observations confirm the presence of the luminous ring first captured in 2017, with a diameter of approximately 43 microarcseconds-consistent with theoretical predictions for the shadow of a 6.5-billion-solar-mass black hole. Notably, the brightest region of the ring has shifted 30 degrees counter-clockwise. "The shift in the brightest region is a natural consequence of turbulence in the accretion disk around the black hole," explains Abhishek Joshi, PhD candidate at the University of Illinois Urbana-Champaign. "In our original theoretical interpretation of the 2017 observations, we predicted that the brightest region would most likely shift in the counterclockwise direction. We are very happy to see that the observations in 2018 confirmed this prediction!"

Orientation

The fact that the ring remains brightest on the bottom tells us a lot about the orientation of the black hole spin. Bidisha Bandyopadhyay, a Postdoctoral Fellow from Universidad de Concepción adds: "The location of the brightest region in 2018 also reinforces our previous interpretation of the black hole’s orientation from the 2017 observations: the black hole’s rotational axis is pointing away from Earth!"

Using a newly developed and extensive library of super-computer-generated images - three times larger than the library used for interpreting the 2017 observations - the team evaluated accretion models with data from both the 2017 and 2018 observations. "When gas spirals into a black hole from afar , it can either flow in the same direction the black hole is rotating, or in the opposite direction. We found that the latter case is more likely to match the multi-year observations thanks to their relatively higher turbulent variability," explains León Sosapanta Salas, a PhD candidate at the University of Amsterdam. "Analysis of the EHT data for M87 from later years (2021 and 2022) is already underway and promises to provide even more robust statistical constraints and deeper insights into the nature of the turbulent flow surrounding the black hole of M87."

Literature reference

The persistent shadow of the supermassive black hole of M87 II: Model comparisons and theoretical interpretations. Door: Event Horizon Telescope Collaboration. In: Astronomy & Astrophysics, 22 maart 2025 [ origineel (open access)]