Astronomers using NASA’s Hubble Space Telescope have spotted for the first time a distant supernova split into four images. The multiple images of the exploding star are caused by the powerful gravity of a foreground elliptical galaxy embedded in a massive cluster of galaxies. This unique observation will help astronomers refine their estimates of the mass of dark matter in the lensing galaxy and cluster. Dark matter is an invisible form of matter that makes up most of the mass of the universe