Loeb, Avi

Avi is Professor of Astronomy and Director of the Institute for Theory and Computation at Harvard; and visiting professor, Weizmann Institute of Science. His research areas include the first stars, black holes, gravitational lensing, gamma-ray bursts, and 21st century cosmology. He was among the dominant theorists to trigger the intense current research on the first stars and quasars. In a series of papers with his students and postdocs, he addressed how and when the first stars and black holes formed and what effects they had on the young universe. Recently, studies of the first sources of light had become one of the most active frontiers in observational cosmology and theoretical cosmology. In addition, he has calculated what seems destined to happen in the far future of the universe when galaxies and their stars recede further and further from one another and the sky grows darker and darker. He showed that extragalactic astronomy will have a limited future; once the universe will age by another factor of ten, our sky will only show the merger product of the Milky-Way and the Andromeda galaxy surrounded by a large vacuum. Loeb showed that, in fact, all sources above a redshift of 1.8 (a certain distance) have already left our event horizon by the present time and we will never be able to communicate with them. Some of his other research includes: how planets can be detected around a star as it gravitationally lenses a background star at galactic distances; a method to overcome the limited precision achievable when observing the cosmic microwave background (CMB) at the edge of the observable universe from our particular viewing point; and how recently discovered hyper-velocity stars (moving at a speed of nearly a thousand kilometers per second in the halo of the Milky Way) as ejections from the Galactic center are caused by a cluster of stellar-mass black holes.