When illuminated by ambient light, the event horizon of black holes will cast a dark shadow. For the supermassive black holes in the Galactic center and in M87, this shadow is detectable with the “Event Horizon Telescope” (EHT), a global mm-wave very long baseline interferometry experiment. The Galactic Center hosts a compact radio source, Sgr A*, with a mass of only 4 Million solar masses, determined precisely from stellar orbits. This gives a robust prediction for a shadow size, allowing detailed tests of general relativity there. However, the imaging is challenging due to rapid source variability and image blurring in the interstellar medium. Imaging of M87 is not affected by these effects, but the black hole mass is more uncertain. With advanced computer simulations the appearance of the sources and their shadows can be modelled and predicted in detail. A first global campaign of the EHT was successfully conducted in 2017 and the data is currently being analysed and we discuss here the first results.
About the speaker:
Heino Falcke has a broad background in theoretical astrophysics as well as experimental radio astronomy and is full professor at the Radboud University in Nijmegen. In 2011, Falcke received the Spinoza award, the highest science award of the Netherlands, and is member of the Royal Netherlands Academy of Arts and Science (KNAW) since 2014. He was honoured with the royal distinction of knight in the order of the Netherlands Lion for his scientific work in 2016.
In 2000, Falcke pioneered the idea of imaging the shadow of the event horizon of black holes with very long baseline interferometry at millimetre-waves (mm-VLBI). For this he received in 2013 a Synergy Grant of the European Research Council of 14 M€ together with two other co-Principal Investigators and established the “BlackHoleCam” project. The grant was given to the top 2% of submitted proposals across all disciplines in Europe. Falcke is founding member and chair of the science council of the global Event Horizon Telescope (EHT) consortium, which conducts first experiments to image black holes and the BlackHoleCam team members are active partners of this consortium.