Helen Sawyer Hogg Public Lecture

The Helen Sawyer Hogg Prize Lecture was initiated in 1985 by the Canadian Astronomical Society with the participation of the Royal Astronomical Society of Canada, the Planetarium Association of Canada, and the Royal Canadian Institute. It continues as an annual public lecture co-sponsored by Cascatrust and the RASC, given alternately at the annual meetings of both societies, in recognition of the sustained and diverse contributions of Helen Sawyer Hogg to public appreciation of the universe around us. Selection of the Lecturer is made by a committee consisting of the Presidents of CASCA and the RASC, and the chairman of the Local Organizing Committee hosting the meeting (either CASCA or RASC).

2021 Helen Sawyer Hogg Public Lecture

Andrea Ghez, University of California, Los Angeles.

From the Possibility to the Certainty of a Supermassive Black Hole

Learn about new developments in the study of supermassive black holes. Through the capture and analysis of twenty years of high-resolution imaging, the UCLA Galactic Center Group has moved the case for a supermassive black hole at the center of our galaxy from a possibility to a certainty and provided the best evidence to date for the existence of these truly exotic objects. This was made possible with the first measurements of stellar orbits around a galactic nucleus. Further advances in state-of-the-art of high-resolution imaging technology on the world’s largest telescopes have greatly expanded the power of using stellar orbits to study black holes. Recent observations have revealed an environment around the black hole that is quite unexpected (young stars where there should be none; a lack of old stars where there should be many; and a puzzling new class of objects). Continued measurements of the motions of stars have solved many of the puzzles posed by these perplexing populations of stars. This work is providing insight into how black holes grow and the role that they play in regulating the growth of their host galaxies. Measurements this past year of stellar orbits at the Galactic Center have provided new insight on how gravity works near a supermassive hole, a new and unexplored regime for this fundamental force of nature.