Hunting for Black Holes

Black holes come in at least two varieties - small stellar-mass black holes and supermassive black holes. The stellar-mass black holes are predicted to form when a massive star dies in a violent supernova explosion. There should be 100 million to 1 billion of these star-sized black holes in our Galaxy; but this number is uncertain by an order of magnitude. The ~25 stellar-mass black holes we have found so far are all in binary systems with a companion star that is dumping hot gas onto the black hole, causing it to glow and flicker in X-rays. Even the recent LIGO discovery of gravitational waves emanated from a binary black hole. Where are all of the isolated black holes? I will present our prospects for finding isolated “free-floating” black holes by using the technique of gravitational lensing. To find the first free-floating black hole, we will need high-resolution infrared images such as those delivered by laser-guided adaptive optics systems on the W. M. Keck Observatory and the future large ground-based telescopes.

Speaker: Jessica Lu, UC Berkeley