Postponed IIHE invited seminar: Putting the hair on black holes

by Prof. Sera Markoff (API/GRAPPA and University of Amsterdam)

Friday 20 Mar 2020, 15:00 → 16:00 Europe/Brussels

Jean Sacton Seminar room (1G003) (IIHE (ULB-VUB))

The physicist John Wheeler once famously said “black holes have no hair”, meaning that a black hole can be characterised by a few numbers like its mass, spin and (not relevant for astrophysical black holes) charge.   However black holes end up having pretty complex “hair" when they manage to gravitationally capture material in a process called accretion, and channel that energy into other forms that can drastically affect their environments.  The most dramatic examples of this energy release are the enormous magnetic plasma structures we call ‘jets’, which can extend well beyond their host galaxy.   These jets are also of great interest for astroparticle physics as the suspected source of ultra-high energy cosmic rays, and possibly also Galactic cosmic rays from smaller, stellar mass black holes that also launch jets.   I am involved in two seemingly very different projects that can study black holes and their consequences:  the Event Horizon Telescope (EHT) and the Cherenkov Telescope Array (CTA), looking at very different scales of the problem.  After a brief introduction to EHT and its key results,  I will discuss how what we are learning is also helping us better understand how the “hairy” astrophysics connects near event horizon regions to the much larger scales relevant for high-energy particle production, which CTA will probe in a few years time.