IISER MOHALI

Abstract: There are about 100 million black holes in our Galaxy, a large fraction of which are freely floating in interstellar space without any stellar companion. Yet, not a single isolated black hole had ever been detected to date. Relativistic deflection offers a powerful, and the only technique capable of detecting isolated black holes. However, the expected deflection is extremely small and can be measured only through large space-based telescopes. We used Hubble Space Telescope to precisely measure the relativistic deflection caused by a black hole as it lensed and deflected the light of a background star. The superb astrometric capability of Hubble Space Telescope allowed us for the first time to measure the deflection caused by a black hole, and thereby measure its mass. Our measured mass of 7 solar mass, coupled with the fact that it emits no light confirmed its black hole nature. The implications of this discovery and the status of our ongoing program will be discussed. Future space telescopes should detect a large number of such isolated black holes.