The brightest supernova in four centuries lit up the southern sky in 1987, but astronomers waited nearly a decade for the ballooning fireball to become large enough–about one-sixth of a light-year–to be resolved from Earth's orbit. With the Hubble Space Telescope astronomers have watched the remnant of the blast develop into a dumbbell-shaped structure consisting of two blobs of debris expanding away from each other at nearly 6 million mph. The structure surprised astronomers. They believe the dim area between the blobs may be related to the equatorial belt of material around the supernova that existed before the star exploded. The ring was illuminated by radiation from the supernova explosion and slowly faded thereafter. However, recently the ring has begun to light up again as debris from the blast crashes into it. The star exploded when its core collapsed and produced a blast wave of neutrinos, which heated the star's inner layers to 10 billion degrees Fahrenheit. This triggered a shockwave that then ripped the star apart and sent the debris hurtling into space. The fireball has since cooled down to a few hundred degrees Fahrenheit, and the debris is now heated by nuclear energy from the decay of the radioactive nuclei produced in the explosion.