What’s in a shadow? Past, Present and Future of Black Hole Imaging

Prof. Dr. Heino Falcke, Radbound Universiteit Nijmegen, Niederlande

The interior of black holes is shielded from observation by an event horizon, a virtual one- way membrane through which matter, light, and information can enter but never leave. This loss of information, however, contradicts some basic tenets of quantum physics. Does an event horizon really exist? What are its effects on the surrounding light and matter? What does a black hole really look like? In 2019, the Event Horizon Telescope (EHT) captured the first-ever image of a black hole, observing its dark shadow in the radio galaxy M87. In 2022, the black hole at the center of our Milky Way was imaged. This confirmed the presence of supermassive black holes at the centers of galaxies and provided strong evidence for the presence of an event horizon.

The EHT will continue to grow as new telescopes join the array. For example, the new Africa Millimeter Wave Telescope (AMT), a 14-meter mm-wave radio dish for VLBI and transient science in Namibia, will pioneer the extension of the EHT to the African continent and greatly improve our ability to make movies of the plasma dynamics around black holes. In the future, space-based interferometers will provide even sharper views by orders of magnitude. The combination of black hole movies, multi-wavelength time domain observations, and a new generation of supercomputer simulations will lead us into a new era of black hole astrophysics. This will allow us to understand the energy generation near the event horizon, the formation of powerful jets, probe the extraction of black hole spin energy, and test fundamental predictions of Einstein's theory of general relativity and its alternatives in the most extreme limit.

Heino Falcke received his Ph.D. summa cum laude from the University of Bonn in 1994. He was PostDoc at the Univ. of Maryland, Visiting Professor at the Univ. of Arizona, Staff Scientist at the Max-Planck-Institute for Radio Astronomy in Bonn and at the Dutch National Radio Astronomy Institute ASTRON in Dwingeloo. Since 2007 he has been full professor of astroparticle physics and radio astronomy at the Radboud University in Nijmegen, the Netherlands. He co-founded the Event Horizon Telescope and was chair- person of its Scientific Council until 2019. Falcke is a member of the Royal Netherlands Academy of Arts and Sciences and a Knight in the Order of the Dutch Lion. His awards include the International Balzan Prize, the Dutch Spinoza Prize, the Henry Draper Medal of the US National Academy of Science, the Amaldi Medal of the Italian Society for General Relativity and Gravitation, and the Herschel Medal of the Royal Astronomical Society in the UK. He has received three European ERC grants to support his work. He wrote the bestselling book "Light in the Darkness: black holes, the universe and us" about the first image of a black hole, which has been translated into ten languages.