Ordinary Meeting - December 2021

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"Planet formation, substructure, and gravitational instability in protoplanetary accretion discs”

Dr Cassandra Hall - Winton (A) Award winner

Over the last 6 years, the Atacama Large Millimeter-submillimeter array has revealed to us a plethora of substructure, such as rings and spirals, present in planet-forming discs. This substructure has a variety of causes, some is due to planets, some is due to gravitational instability, and some is still a mystery waiting to be solved. In this talk, I highlight some recent advances in diagnosing the origins of these substructures, and future predictions for instruments scheduled to come online over the next decade.

Dr. Cassandra Hall is an Assistant Professor of Computational Astrophysics at the University of Georgia, USA. She is primarily a computational astrophysicist, using simulations to interpret and understand observational data. She earned her doctorate at the University of Edinburgh in 2017, and became one of two people in the inaugural class of Winton Exoplanet Fellows, a program to support outstanding postdoctoral researchers working in exoplanet research. She relocated to the University of Georgia in 2020, where she now leads an exoplanet and planet formation research group. She was awarded the University of Georgia's Lilly Teaching Fellowship in 2021 for dedication to teaching excellence with a commitment to equitable practices in teaching


“The First Image of a Black Hole from the Event Horizon Telescope”
Dr. Ziri Younsi (UCL)

Group Award (A): The Event Horizon Telescope (EHT) team

A black hole is one of the most mysterious yet simple objects in nature, possessing a gravitational field so intense that it warps space and time around it, and is characterised by an event horizon, wherein even light cannot escape. In spite of overwhelming indirect evidence of their existence, until recently they had evaded direct observational confirmation. In 2019, the Event Horizon Telescope (EHT), an international collaboration of over 60 universities and institutes spanning six continents, astonished the world by publishing the first ever picture of a supermassive black hole. By linking radio telescopes around the world, a virtual Earth-sized telescope was created, achieving unprecedented levels of angular resolution which enabled us to produce this groundbreaking picture of the black hole in the heart of the galaxy Messier 87 (M87).

In this talk I will begin by presenting an overview of our present knowledge of the physics of matter and radiation near the event horizon, outlining how this knowledge informed the collaboration's theoretical modelling of black-hole images and underpinned the EHT's measurement of M87's black hole. I will then explain how the EHT performed these pioneering measurements and produced the first image of a black hole. Finally, I will discuss some of the exciting ongoing and future scientific prospects for the imaging of black holes.

Dr. Ziri Younsi is currently a UKRI Stephen Hawking Fellow in Astrophysics at University College London (UCL), who has been working within the Event Horizon Telescope collaboration since 2014. Younsi has been, developing and performing supercomputer simulations of black holes and horizon-scale black-hole imaging, enabling comparison with, and interpretation of, observational images of black holes. He is one of just three UK scientists on the Event Horizon Telescope team and is a co-recipient of the National Science Foundation Diamond Achievement Award, the 2020 Breakthrough Prize for Fundamental Physics, and the RAS's Group Award.


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