Seminar – Dr Roger Deane (UP)

May 16, 2019 @ 12:00 pm – 1:00 pm

Title:  Imaging black hole shadows with the Event Horizon Telescope



When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. On 10 April 2019, the Event Horizon Telescope Collaboration revealed the first image of this black hole shadow. This required a large international effort from over 200 scientists spread across five continents, using a global very long baseline interferometry array observing at a wavelength of 1.3 mm. The instrument achieves an angular resolution of ~20 μas and resolves the central compact radio source at the heart of the giant elliptical galaxy M87 into a bright emission ring with a diameter of 42 ± 3 μas. Overall, the observed image is consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity.  This image thus provides powerful evidence for the presence of supermassive black holes in centres of galaxies and as the central engines of active galactic nuclei. The EHT is clearly a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible. In this talk, I will provide an overview of the instrument, the techniques developed to achieve its scientific objectives, discuss a few of the key inferences from these first results, and look to the future of this exciting field.