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Currently Playing: Constraining Black Hole Models with EHT Observations | Event Horizon Telescope

Einstein's theory of general relativity predicts the existence of black holes. By solving Einstein's equations in vacuum, K. Schwarzschild and R. Kerr were able to obtain the descriptions of the spacetime geometry outside a nonrotating and a rotating black hole respectively. These black holes drastically curve spacetime in their vicinity, possess event horizons, from behind which no light or matter can escape, and thus cast dark shadows. All these features vary in magnitude with changing black hole spin. Alternative theories of gravity also similarly predict black holes. Naturally, these black holes can be different from the Kerr black holes of general relativity, and in particular cast shadows of different sizes, depending on their spin or "generalized charge" (also called "hair"), sometimes smaller or larger than any Kerr black hole would. Today, we reveal a significant step in testing well-known black hole models and theories with the Event Horizon Telescope. Towards this end we compared the theoretically-predicted shadow sizes associated with various solutions against the 2017 measurements of M87*, and were able to extract constraints on their viability in describing M87*.We demonstrate, e.g., that the quality of the measurements is already sufficient to rule out that M87* is a highly charged-dilaton black hole from a particular string-inspired theory of gravity. At the same time, the shadow size of M87* is entirely consistent with that of a Kerr black hole. The Event Horizon Telescope (EHT) is an international collaboration that captured the first image of a black hole by creating a virtual Earth-sized telescope. To learn more, you can check out our website at https://eventhorizontelescope.org/. Follow us on Twitter: https://twitter.com/ehtelescope Follow us on Facebook: https://www.facebook.com/ehtelescope/ Or follow us on Instagram: https://www.instagram.com/ehtelescope/ If you enjoyed this video, please like, comment, and subscribe! Credit: Producers: Goethe University Frankfurt Directors: Prashant Kocherlakota, Luciano Rezzolla Writers: Prashant Kocherlakota, Luciano Rezzolla Editors: Prashant Kocherlakota, Luciano Rezzolla, and the EHT Outreach Working Group Narrator: Nicola Barber Animation: Fiks Film Funded with support from the European Research Council and Goethe University Frankfurt. Realised under the auspices of the Event Horizon Telescope.