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STScI Webcast

John Bahcall Lecture Series

The Galactic Center: Unveil

Presented by: Andrea Ghez (UCLA)
Category: Science Colloquia   Duration: 1 hour and 45 minutes   Broadcast date: April 10, 2013
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The proximity of the center of our Galaxy has presented us with a unique opportunity to study a galactic nucleus with orders of magnitude higher spatial resolution than can be brought to bear on any other galaxy. This advantage, along with the recent advances in high angular resolution imaging technologies, has allowed the first observations of individual stars at the very heart of a galaxy. After more than a decade, such observations have transformed the case for a supermassive black hole at the Galactic center from a possibility to a certainty, thanks to measurements of individual stellar orbits. The rapidity with which these stars move on small-scale orbits indicates that 4 million times the mass of the sun resides within a region comparable to the size of our solar system and provides the best evidence yet that supermassive black holes, which confront and challenge our knowledge of fundamental physics, do exist in the Universe. Subsequent high-resolution imaging studies of the Galactic center have shown that the stellar population near our Galaxy’s supermassive back hole is quite different from the predications of theoretical models for the interaction between central black holes and their environs ( an essential input into models for the growth of nuclear black holes). In particularly, the observations have revealed an abundance of young stars in a region that is inhospitable to star formation and, conversely, a dearth of old stars where as a stellar cusp is expected. Further improvements in measurement precision should enable tests of Einstein’s theory of General Relativity in the extreme environment near a supermassive black hole.