BRIGHT SUPERNOVA EXPLAINED

In 2010 astronomers observed a supernova, called PS1-10afx, that was shining 30 times brighter than any other supernova - exploding star -  in its class. It was thought that it may be a completely new type of stellar explosion.
http://www.bbc.co.uk/news/science-environment-27118405

However, a team at the University of Tokyo's Kavli Institute suggested that PS1-10afx was a normal type 1a supernova magnified by a lens in the form of a supermassive black hole nearby, in the direct line of sight between Earth and the supernova. Light rays from the supernova were bent by a warping of spacetime around the black hole, creating four separate images of the supernova viewed from Earth, which were observed as a single image due to atmospheric blurring.  

Dr Robert Quimby said 'We had no direct evidence for the lens. Looking at the spectra, we could check to see if there was light coming from two sources at two separate distances, which is what we found.' The Keck telescope in Hawaii observed the host galaxy of PS1-10afx.

The discovery could provide astronomers with a new tool to measure the expansion of the universe, because each image will arrive at a different time and the precise delay depends on how fast the universe is expanding.

Professor Masamune Oguri of the University of Tokyo said 'Our discovery implies there are many more gravitationally lensed supernovae that are barely resolved, like PS1-10afx'.