Observing the unobservable: a multi-messenger view of black holes in the Event Horizon Telescope era Event

Black holes are one of the strangest byproducts of Einstein's Theory of General Relativity:
objects so compact that not even light can escape. However when they do manage to
"harvest" nearby material, they can channel this energy into several new forms that emit
particles and radiation across the entire electromagnetic spectrum. Thus to fully understand
black holes we need to combine information from light and particle signals into a coherent
picture. Furthermore, the event horizon leads to a prediction that if we only had a good
enough telescope, we should see a ring of light surrounding a dark "shadow" indicating that
point of no return. In 2017 the Event Horizon Telescope (EHT), a planet-sized array of radio
telescopes, managed to resolve this feature for the solar system sized supermassive black hole
in the M87 galaxy, and for the supermassive black hole in our own Milky Way, Sgr A*. After a
brief overview of the key questions we have about black holes and their role in the Universe, I
will put the ongoing EHT results into the context of our cutting edge understanding of black
holes. In particular I will explore why we need to combine these new images of black holes
with other "messengers" like light from telescopes observing at other frequencies, and
particles like neutrinos

Biography: Sera Markoff is full professor of theoretical high-energy astrophysics and
astroparticle physics at the University of Amsterdam, where she joined the faculty in 2006.
Before that she was an A.v. Humboldt Research Fellow at the Max Planck Institute for Radio
Astronomy, and a U.S. National Science Foundation Astronomy & Astrophysics Postdoctoral
Fellow at M.I.T.. Prof. Markoff is an internationally recognised expert in compact object/black
hole studies, ranging from the development of complex multi-messenger observations to
modelling and interpretation. She is a founding member of the Event Horizon Telescope
Collaboration (EHTC) and its Science Council, where she served most recently as Vice-Chair, and
as of 2024 is member of its new Science Board. She also co-coordinates the EHTC Multi-
Wavelength Science WG, and is a member of the Cherenkov Telescope Array Consortium,
where she served as its first Multi-Wavelength/-Messenger WG Convener. Her research, as well
as her public outreach efforts, have been recognised by several prizes, including being named
Fellow of the American Physical Society, the Dutch Research Council VIDI and VICI Personal
Career Awards, the Willem de Graaff Prize for Public Outreach of the Royal Dutch Astronomical
Society, an ERC Synergy Grant “Blackholistic” and Member of the Royal Netherlands Academy
of Arts and Sciences. As part of the EHTC she also shared several other major prizes such as the
Breakthrough Prize in Fundamental Physics, the Rossi Prize and the Einstein Medal.

Image credit: Event Horizon Telescope Collaboration