Several months ago, we wrote about the discovery of Supernova Refsdal, an exploding star in a faraway galaxy, whose light had split into four images on its way to Earth.
Now astronomers have used the Hubble Space Telescope to spot the supernova — again! On December 11th, Patrick Kelly (University of California, Berkeley) and colleagues spotted a fifth image of the exact same explosion, more than a year after Hubble caught the previous four images.
The time travel trick occurs by way of gravitational lensing. The gravity of a massive object magnifies light sources in just the right place behind it and may distort or split their images.