| Jan 22, 2025 |
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(Nanowerk News) Using observations from 2017 and 2018, the Event Horizon Telescope (EHT) Collaboration has advanced our understanding of the supermassive black hole at the centre of Messier 87 (M87*). This study marks a significant step towards multi-year analysis at horizon scales, in order to investigate the Black Hole’s turbulent accretion flow. It utilizes a vastly improved set of simulations a factor of three larger than previous ones. The results include major contributions from the MPIfR in Bonn, Germany.
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The findings have been published in Astronomy & Astrophysics (“The persistent shadow of the supermassive black hole of M87. II. Model comparisons and theoretical interpretations”).
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“This study highlights the significance of incorporating larger and more diverse simulation sets in the investigation of the supermassive black hole,” explains Christian M. Fromm, member of the EHT theory group and affiliated with the University of Würzburg and the MPIfR. “By integrating multi-epoch data with advanced models, we can better understand the dynamical processes driving the brightness variations observed near M87*. This approach paves the way for future studies focusing on the complex interplay of plasma dynamics and black hole spin.”
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| Observed and theoretical images of M87*. Left: EHT images from the 2018 and 2017 observation campaigns. Middle: images from a general relativistic magnetohydrodynamic simulation. Right: the same simulation, blurred to the EHT’s observational resolution. (Image: Hung-Vi Pu)
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Hung-Yi Pu, assistant professor at National Taiwan Normal University, adds, “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. This work highlights the transformative potential of observing the black hole evolving in time.”
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The 2018 observations confirmed the luminous ring seen in 2017, with a diameter of about 43 microarcseconds, matching theoretical predictions for the shadow of a 6.5 billion solar-mass black hole. The brightest part of the ring is shifted 30 degrees counter-clockwise, due to turbulence in the accretion disk. This behaviour is consistent with predictions from the 2017 analysis, which expected such a shift.
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Using a synthetic data set three times larger than in 2017, the EHT team analysed accretion models from both years. When gas spirals into a black hole, it can align with or oppose the spin of the black hole. The observed changes are better explained by gas flowing against the rotation of the black hole.
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“The 2018 observations, in conjunction with 2017 data, reveal a nuanced picture of M87*’s accretion flow,” states Eduardo Ros, scientist at MPIfR. “The study underscores the evolving nature of the plasma structures near the event horizon, offering clues about the variability mechanisms that govern black hole environments. This iterative process of modeling and observation is critical for unraveling the mysteries of black hole environment dynamics.”
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This new understanding is particularly significant in light of the complementary observations of the black hole’s shadow by the Global Millimeter VLBI Array (GMVA) in 2018, which were presented in April 2023. “These observations at 3 mm wavelength, combined with the EHT’s findings at 1.3 mm wavelength, provide a more complete picture of the black hole’s environment and its dynamics,” adds Thomas P. Krichbaum, also scientist at the MPIfR and member of the team of researchers.
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Ongoing analysis of EHT data from later years (2021 and 2022) aims to provide stronger statistical constraints and deeper insights into the turbulent flow around M87*.
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J. Anton Zensus, director at the MPIfR and founding chair of the EHT collaboration, notes, “These results are based on the continuous work of the EHT and are confirmed in the investigations with the GMVA. They show how important global partnerships, state-of-the-art technologies and persistent research are for scientific progress.”
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