Speaker: Prof. Andrea M. Ghez, University of California Los Angeles
Place: Holcblat
Time: Wednesday, 19/May/2004, 14:00
Unveiling a Supermassive Black Hole at the Center of our Galaxy
Abstract
I will discuss recent observations that reveal the presence of a supermassive black hole in the center of our Galaxy. The evidence is based on forefront infrared observations with the W.M. Keck 10-meter telescope employing new "adaptive-optics" technology that overcomes atmospheric distortions, providing high-resolution images at the diffraction-limit of the telescope. The orbital motions of individual stars around the black hole have been measured, and they pinpoint the precise location of the black hole, and determine its mass of 4 million times that of the Sun. Detailed spectroscopy reveals the puzzling presence of young stars very close to the black hole. The stars may provide key insight into the growth of the black hole. Thermal infrared imaging has revealed variability on timescales as short as 40 minutes, a likely signature of hot plasma within only 80 Schwarzchild radii of the event horizon.