Lecture Series 2011-2012 - “At Last: Seeing Supermassive Black Holes Shred Stars” - Glennys Farrar

Friday, February 10, 2012

Dr. Glennys Farrar, professor of physics at NYU, will address the AAA Friday, February 10, on “At Last: Seeing Supermassive Black Holes Shred Stars.” The free public lecture begins at 6:15 p.m. in the Kaufmann Theater of the AMNH.

“A very exciting new frontier has been recently opened: the observation of the ‘stellar tidal disruption’ phenomenon,” Farrar told Eyepiece.

“About once every 100,000 years, a star passes so close to the supermassive black hole (SMBH) at the center of its galaxy that it is torn apart by the gravitational force, without being so close that the debris completely falls into the hole.

“When this happens, an extremely bright flare is generated that lasts weeks to months, something like a transient quasar. The observational challenge is to distinguish the flares from far-more-common supernovae and variable active galactic nuclei. Yet the payoff is tremendous, because the probability and properties of tidal disruption flares (TDFs) depend on the spin and mass of the black hole; so that a large database of TDFs will allow a census to be performed of SMBHs, including determining distribution of spins and masses. These are critically important in understanding the evolution of the universe, yet extremely difficult to determine with any other technique.

“TDFs are also valuable for the insight they will give to the production of jets in quasars and gamma-ray bursts, and the possibility they are the sources of ultrahigh-energy cosmic rays.

“This talk will describe the discovery of the first two definitive examples of TDFs using optical techniques, in archival Sloan Digital Sky Survey data, and the requirements for future searches to do a successful census of SMBHs with this technique. The remarkable flare seen by the Swift X-ray telescope last year—likely to be an example of a TDF viewed in ‘blazar mode’—and theoretical efforts to model such flares will also be discussed.”

Farrar received her Ph.D. in theoretical physics from Princeton in 1971, breaking the gender barrier in physics there in the process. She was a member of the Institute for Advanced Study and on the faculties of CalTech and Rutgers before moving to NYU in 1998.

Among her accomplishments in particle physics, Farrar is perhaps best known for pioneering the phenomenological study of supersymmetry (SUSY). With colleagues, she developed most present search techniques for superparticles, gave the first limits on SUSY breaking and superpartner masses from accelerator experiments and precision observables, and initiated the study of cosmological effects of SUSY. She made a number of predictions the experimental confirmation of which played an important role in establishing the Standard Model.

Farrar’s current work focuses mainly on problems at the intersection of astrophysics, cosmology, and particle physics—including ultrahigh-energy cosmic rays, the nature of dark matter and dark energy, and the origin of the asymmetry between matter and antimatter. Another thrust of NYU research is to improve simulation and reconstruction of cosmic-ray air showers. Farrar is now engaged in several projects, including use of observations of large-scale structure and galactic dynamics to constrain the possibility that dark matter experiences nongravitational forces.