On November 11, 2014, astronomers everywhere were treated a rather rare case of cosmic fireworks. A very distant star ended its life in a giant explosion of light which we call a supernova. Supernovae have been spotted as 'new' or 'guest stars' by humans looking up into space since ancient times, and can be so bright that occasionally a supernova can be seen from half-way across the universe with the unaided eye.
What was rare about the supernova event on November 11, 2014, is not actually that the star exploded. All stars that are at least 2-3 times the mass of the Sun end their lives in this dramatic way. What is extremely lucky for us is that this supernova event happened to be situated behind an object which acts as a natural telescope in space. This natural telescope, also known as a lens, can play optical illusions on us. In this case, the lens boosted the brightness of this already bright stellar explosion. The lens also literally photocopied the image of the supernova into four different places on the sky. As a result, instead of spotting one bright and apparently new 'star' in the sky, a total of four bright lights are seen. A supernova which is photocopied on the sky is so rare that only a total of one event (this one) has ever been discovered. Astronomers everywhere are racing to observe the fading light of the four copies of this stellar explosion before the supernova disappears from view. On a historical note, such 'lensed' events were first predicted by Einstein as a natural consequence of the Theory of General Relativity.