This Hubble telescope image shows SN 1987A's triple-ring system, including the bright spots along the inner ring of gas surrounding the exploded star. A shock wave of material unleashed by the stellar blast is slamming into regions along the inner ring, heating them up, and causing them to glow. The ring, about a light-year across, was probably shed by the star about 20,000 years before it exploded. Credit: NASA, ESA, P. Challis and R. Kirshner (CfA)