Studying nearby supermassive black holes at the event horizon scale

17/08/2022 - 14:00 - 15:00
Auditório "Prof. Dr. Paulo Benevides Soares", Bloco G. Com transmissão pela internet
Studying nearby supermassive black holes at the event horizon scale
Ciriaco Goddi 
One of the most extreme and elusive consequences of Einstein's general theory of relativity (GR) is the existence of black holes. Very recently, the EHT Collaboration unveiled the first image of the supermassive black hole at the center of our own Milky Way galaxy, Sgr A*. The image comes three years after the first historical image of a black hole, the one at the center of the distant galaxy Messier 87 (named M87*). Both images were produced using observations from a worldwide network of radio telescopes, comprising the Event Horizon Telescope. The two black holes look remarkably similar, despite residing in two completely different types of galaxies and having very different black hole masses (roughly 4 millions and 6.5 billion solar masses, respectively). Both images show a bright ring formed as light bends in the intense gravity around the black hole. The ring encloses a dark region at its center, the so-called black hole 'shadow', which is the signature of an event horizon, the defining feature of a black hole. Overall, the size and shape of the observed images are consistent with expectations for the shadow of a spinning (Kerr) black hole as predicted by GR. In the talk, I will describe the context, the meaning and the 'behind the scenes' of these breakthrough discoveries.
Ciriaco got his PhD from Cagliari University in Sardinia (Italy) and has conducted postdoctoral research at the Harvard-Smithsonian Centre for Astrophysics (USA) and the European Southern Observatory (ESO) as ESO Fellow (Germany). He has served as Project Scientist of the ERC-funded BlackHoleCam project at the Radboud University Nijmegen and as Support Scientist in the ALMA Regional Center Dutch Node at Leiden Observatory in The Netherlands.