Pancharatnam Lecture

Snap, Crackle and Pop: Flares, Variability and Caustics from the Black Hole in M87

Speaker: Roger Blandford (Stanford University, California)

Date and time
Webinar link
Pancharatnam Lecture
Venue
RRI Auditorium

Abstract

The close by, massive, jet-forming black hole in the nucleus of the galaxy M87 has been famously imaged by the Event Horizon Telescope. This has been generally interpreted in the context of an orbiting ring of gas that glows steadily. An alternative class of ``ergomagnetosphere models posits that the magnetic field strength is much greater and we are observing individual flares associated with the ``snapping'' of magnetic field. If so we expect see this reflected in the spectral-temporal-ploarization behaviour or ``crackle’’ measured. Typical flares may be accompanied by fainter echoes which can also be sought statistically and individually. A spinning black hole will associate a characteristic caustic surface with the observer. A small spark within the ergomagnetosphere can traverse this caustic, forming four highly-magnified images which move rapidly around the Einstein ring. in a generic fashion. These occasional ``Pops’’ are also being sought in existing data. A simplified description of geometric optics in Kerr spacetime will be presented and the various observable consequences of having a strong magnetic field will be outlined with a view to inferring the sources of emission. Application to other black hole sources will be outlined.

Poster

Short Biography
Roger Blandford is the Luke Blossom Professor in the School of Humanities and Sciences, and Professor of Physics and of Particle Physics and Astrophysics, Stanford University, in the Kavli Institute for Particle Astrophysics and Cosmology. He obtained his PhD from the University of Cambridge, UK and has been a faculty first at CalTech and later at Stanford University. His scientific research has addressed a wide range of problems in the physics of black holes. Among his best known findings are the Blandford-Payne and Blandford-Znajek processes that explain the production of powerful jets from black hole systems and the Blandford-Konigl model that enhanced the understanding of their structural and spectral properties. His discoveries have been acknowledged by numerous awards over the decades, including the Helen B. Warner Prize, the Dannie Heinemann Prize, the Eddington Medal, the Crafoord Prize and the Shaw Prize. He established the first new Kavli Institute for astrophysics research in Stanford University in 2003 as its first director. He also chaired the Decadal Survey of Astronomy and Astrophysics of the National Academy of Sciences of the United States in 2010.