Physics Colloquium: Stepping into the light with high power lasers and brilliant gamma beams
Prof. Sydney Gales, IPN Orsay
The Emilio Segre Distinguished Lectures in Physics of the Raymond and Beverly Sackler Foundation
Professor Judah M. Eisenberg Memorial Lecture
The Center of our Galaxy is a unique laboratory for exploring the astrophysics around a massive black hole and testing General Relativity in this extreme environment. I will discuss the results of a major campaign of observing the Galactic Center in 2017/2018 with three instruments at the European Southern Observatory's VLT, including the novel GRAVITY interferometric beam combiner of the four 8-meter telescopes. During this period the B-star S2 completed a peri-passage at ~1400 Schwarzschild radii around the compact radio source SgrA*, and permitted for the first time a test of the equivalence principle and the detection of the first post-Newtonian orbital elements in a classical 'clock experiment' around a massive black hole. During bright states ("flares") we detect centroid motions and polarization changes of the infrared emission of SgrA* itself. These can be well fitted by near face-on, circular orbits near the innermost circular orbit (ISCO). The mass inferred at ISCO is the same as that within the S2 orbit, further strengthening the evidence that SgrA* is a Kerr black hole.
I will conclude by summarizing some of the extragalactic results with GRAVITY and the possibility for future upgrades of optical interferometry.
Event Organizer: Dr. Ishay Pomerantz