Once Goobar determined that the brightness and apparent distance wasn't a measurement error, he realized it must be caused by a phenomenon called a gravitational lens, he said. In this kind of situation, instead of getting in the way, a galaxy in between the telescope and supernova can actually focused a sharper view of the faraway object. You can see a video overview of how gravitational lenses work here.
"The huge amplification of the supernova light requires a remarkable alignment of the lens in between the supernova and us — the odds are something like one in a hundred thousand!" Goobar said. [Supernova Photos: Amazing Views of Star Explosions]
After the discovery, researchers rushed to turn other telescopes toward the supernova blast, as the glow might last for only a matter of weeks. The director of the Hubble Space Telescope offered discretionary observation time that had been set aside, reserved for unexpected discoveries, and the Very Large Telescope in Chile offered similar resources. Astronomers at the Keck Observatory in Hawaii offered some of their assigned observing time to the project, as well, Goobar said.
The supernova happens to be a type of star explosion called 1A, which shines at a consistent brightness and can be used to judge distances across the universe. Because the supernova was of this type, researchers could calculate that the light traveled 4.3 billion years to reach the telescopes. Along the way, the light got a boost from a galaxy positioned between Earth and the supernova.
Objects' gravity warps space-time according to Einstein's general theory of relativity, and the more massive the object, the greater the warping effect. Like curved lenses made of glass bend the light that passes through them, this galaxy's gravitational pull bent the light of the supernova as it passed by. And the galaxy happened to be perfectly aligned to focus four different streams of the supernova's light into Earth's view. It is the first time such a "standard candle" type 1A supernova has been split into multiple images by a gravitational lens, Goobar said.