Popular Science takes a wide-eyed look at gravitational lensing, the phenomenon responsible for splitting this supernova into four different images in the night sky:
But in between this supernova and Earth, there happens to be a massive galaxy, within a cluster of galaxies, which has had an interesting effect on the path of the light coming from this exploded star.
Using the Hubble Space Telescope, researchers from the University of California, Berkeley observed the galaxy’s gravitational lensing effect on the supernova’s light. Because the galaxy is so massive, it warps space-time around it, which bends the light as it travels to Earth. As a result, the galaxy creates four separate images of the supernova it its edges—a phenomenon called an Einstein’s Cross.
Since four images arise, it means the supernova is almost exactly behind the galaxy in relation to us. When light from a distant object passes by an extremely massive object, the warped space-time changes the direction of the light, disrupting it from traveling in a straight line. A less-than-perfect alignment of these objects—which occurs most of the time—produces distortion like arcs and filaments. But as the Earth, the galaxy, and the supernova all lie in a line, the light’s path is disrupted perfectly, making it appear in numerous distinct places around the galaxy.
Images at the link.