Unusually bright supernova explained by gravitational lensing

Ars Technica : Type Ia supernovae are used to determine intergalactic distances because the characteristics of their explosions are very consistent. When supernova PS1-10afx was spotted in 2010, it was determined to be 400 times brighter than expected. Because it was so significantly anomalous, it could have threatened the use of type Ia supernovae as standard candles for distances. Superluminous supernovae are as bright as PS1-10afx, but its other characteristics ruled it out as superluminous. Robert M. Quimby at the University of Tokyo and his colleagues used the Keck telescope in Hawaii to monitor the area of the supernova since its detection. They found a galaxy between it and Earth that they were able to determine had gravitationally lensed the light from the supernova. This is the first time such lensing has been detected, and it also explains away the anomalous nature of the supernova.