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Physics Professor Hung-Yi Pu Joins GMVA International Research Team to Unravel Black Hole Mysteries

In collaboration with the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) and several international research teams, Assistant Professor Hung-Yi Pu of the Department of Physics at National Taiwan Normal University participated in a multinational research project. The project successfully obtained images using a new millimeter-wavelength observation to confirm for the first time ever the connection between accretion and jet formation near supermassive black holes at the center of galaxies. The results were published in the April issue of Nature, a leading international journal, helping to raise Taiwan's profile internationally.

In order to observe black holes, a global collaboration of scientists established two international projects, linking telescopes around the world to form one virtual telescope as large as the Earth. This global network of synchronized radio telescopes includes the Event Horizon Telescope (EHT) and the Global mm-VLBI Array (GMVA), each at a different wavelength band. EHT uses 1.3 mm wavelength observations to obtain images of black hole shadows, and GMVA uses 3.5 mm wavelength observations to capture the nature of black hole accretion and nearby jets. The first and second images ever of black hole shadows recorded in human history, produced by EHT, were published in 2019 and 2022.

According to the Academia Sinica, the imaging of black hole accretion and nearby jets is the result of Atacama Large Millimeter/Submillimeter Array (ALMA) and Greenland Telescope (GLT) joining in the GMVA observations in 2018. “By having GLT and ALMA as a part of the global VLBI array at 3.5mm, we were able to reach a sufficient angular resolution to resolve the nuclei into the thicker and larger ring in comparison with EHT results, mainly associated with the spatial resolved accretion flow surrounding the super massive black hole of M87,” says Keiichi Asada, Associate Research Fellow at ASIAA and one of the corresponding authors of this paper.

NTNU’s Department of Physics Assistant Professor and Yushan Young Scholar Hung-Yi Pu, who led the theoretical model for the paper, explained that this research result relies on high resolution observations at different frequencies: “Using numerical simulations of the black hole environment and a theoretical model of the radiation characteristics of the black hole system, we determined that the ring structure in the image is related to the accretion flow.”

This is not the end for the exploration of the M87 black hole, as further observations by a series of powerful telescopes will continue to unlock its secrets. 

Original link to the publication in Nature: https://www.nature.com/articles/s41586-023-05843-w