Supernova I987A

Astronomers around the world were excited when, on 24 February 1987, a new naked-eye star suddenly appeared within the Large Magellanic Cloud. It was the first supernova seen with the unaided eye since 1604, reaching magnitude 2.9 at its peak and remaining visible for several months. The object was originally a massive blue star called Sanduleak -69 202.
The star actually exploded some 165,000 years ago, the light having taken that long to reach us. The light was accompanied by a burst of neutrinos—tiny, elusive particles. Scientists had predicted that these would be produced in very large numbers during a supernova explosion.
The study of SN 1987A continues today, with rings of light, shown in the illustration of the Hubble Space Telescope image (right), being the most recent surprises in the ongoing tale of the supernova's discovery.