Gravitationally Lensed Supernovae

Light from distant astronomical sources is deflected by space-time curvature, as described by Einstein’s theory of General Relativity. Close alignment between the light source, intervening matter and the observer at Earth can result in significant enhancement of the measured flux. This phenomenon, known as gravitational lensing, can be used to study distant faint sources, as well as the properties of the objects acting as lenses. Furthermore, time-delay measurements between lensed images of supernova explosions can be used to measure the Hubble constant, i.e., the expansion rate of the Universe. Various recent results involving gravitational lensing of supernovae will be discussed, including the discovery of the first multiply-imaged “standard candle” supernova, iPTF16geu. An intriguing realization is that supernova searches, even from astronomical facilities with rather poor angular resolution, can locate extremely rare astronomical systems exhibiting strong gravitational lensing, and probe angular scales too small to be resolved even by the sharpest space observatories.