Origins Institute Lecture Series with Dr. Kailash C. Sahu

A Census of Exoplanets in the Milky Way through Gravitational Microlensing

More than 5000 exoplanets have been discovered to date through a variety of techniques, most of which are nearby --- within ~500 parsecs from the Sun, and orbiting relatively close to their parent stars. Gravitational microlensing provides a powerful technique to detect planets around faraway stars, and also planets orbiting at large distances from their parent stars. After an introduction to microlensing, Dr. Sahu will discuss the results from PLANET (Probing Lensing Anomalies NETwork) and other microlensing networks. He will then discuss our SWEEPS transit program which used the Hubble Space Telescope to look for planets around stars in the Galactic Bulge, leading to the detection of 16 candidate planets through their transit signals. These programs suggest that planets outnumber the stars in our Galaxy. Finally, he will discuss how the upcoming Roman telescope will significantly advance the field by detecting thousands of exoplanets through microlensing.

Dr. Sahu is an astronomer at the Space Telescope Science Institute, and an instrument scientist for HST. His research efforts have focused on applying microlensing, transit, and relativistic deflection techniques to detect and study exoplanets, nearby stars and black holes. He currently leads two HST projects to detect isolated, stellar-mass black holes and determine their masses through gravitational lensing.

He led the first ever measurement of relativistic deflection caused by a star outside the solar system, as predicted by Einstein just over a century ago, and measured the mass of the nearby white dwarf Stein 2051 B--- the first mass measurement through this technique (Sahu et al. 2017, Science 356, 1046). This work was listed by Discover magazine as one of the “Top 100 Science Stories” of 2017. Dr. Sahu has over 300 scientific publications, including 9 in Nature and one in Science.