Supernova SN 1987A. Ultraviolet image taken by the Hubble Space Telescope (HST) of the supernova SN 1987A (bright at centre) surrounded by a circular shell of gas. A foreground star is at bottom left. In a supernova explosion the star's centre collapses in a few seconds and a wave of energy blows the star apart creating a remnant (circular shell) composed of gas and debris from the original star. SN 1987A was discovered on February 23rd 1987 in the Large Magellanic Cloud, at a distance of about 155,000 light years. The image was taken after HST was serviced to remove the aberration that was affecting its optics.