Niels Bohr Lecture by Suvi Gezari, Space Telescope Science Institute and Johns Hopkins University

Black Holes Snacking on Stars

Abstract: Supermassive black holes are mysterious and powerful phenomena of extreme gravity that lurk in the centers of almost all galaxies, including our own Milky Way.  We cannot detect light directly from a black hole: its gravitational pull is so strong in its vicinity that even light cannot escape it, the region known as the event horizon of a black hole. 

However, astronomers have made exciting advances in our ability to study supermassive black holes indirectly, either from witnessing the gravitational pull on stars and gas nearby the black hole, or by observing light emitted by stars and gas in the process of being swallowed by the black hole.  

In the near future, we will be able to detect merging binary supermassive black hole systems via gravitational waves, providing a new window into massive black hole evolution over cosmic time.

In my talk, I will highlight how we hunt for supermassive black holes by watching them snack on unlucky stars that wander too close-by in the nucleus of a galaxy.  I will show the bounty from our hunt using telescopes on the ground and in space that survey the dynamic night sky, and how we plan to use these star-feeding events to probe the demographics of supermassive black holes in galaxy nuclei, and to answer the fundamental question of how they first formed in the early Universe.

Biography:

Dr. Gezari is an Associate Astronomer with tenure, and the Chair of the Science Staff at the Space Telescope Science Institute in Baltimore, MD and a Research Professor in the Department of Physics and Astronomy at Johns Hopkins University. 

Before arriving at the institute, Dr. Gezari was an Associate Professor of Astronomy with tenure at the University of Maryland and the co-director of the Joint Space Sciences Institute. 

She was awarded the Kavli Foundation Prize Plenary Lecture at the 235th AAS Meeting in Honolulu, HI in January 2020 for her global leadership in the study of tidal disruption events, received the University of Maryland College CMNS Board of Visitor’s Junior Faculty Award in 2016, was a Scialog Time Domain Astronomy Fellow in 2015, and received an NSF CAREER Award in 2015.  Prior to her faculty position she was a Hubble Fellow at Johns Hopkins University. 

• She received her bachelor’s of science degree in Math-Physics, with honors at Brown University in 1999.
• Dr. Gezari’s research program harnesses the power of time domain observations to study supermassive black holes. 
• Dr. Gezari is a pioneer in observational studies of tidal disruption events (TDEs), luminous outbursts from the nuclei of galaxies that occur when an unlucky star is ripped apart and consumed by a central massive black hole. 
• She has used wide-field time domain surveys to discover TDEs, including GALEX, Pan-STARRS1, iPTF, ZTF, and soon with Rubin, Roman, ULTRASAT and UVEX. 

Dr. Gezari uses follow-up observations across the electromagnetic spectrum, especially in the UV and X-rays, and spectroscopic observations of their host galaxies, to classify and characterize the events, and use them as probes of accretion physics and massive black hole demographics.