Onset of Titanic Collision Lights Up Supernova Ring

Fast-moving debris ejected from an exploding star is finally beginning to deliver a "knockout punch" to a ring of material surrounding the site of the violent death. The Hubble telescope is giving astronomers a ringside seat to this celestial spectacle unfolding in a nearby galaxy called the Large Magellanic Cloud. The collision is causing the gases in the ring surrounding the exploding star, called supernova 1987A, to glow as they are heated to millions of degrees and compressed by the sledgehammer blow of a 40-million-mile-per-hour blast wave. Hubble's sharp view revealed four bright knots of heated gas at places that had been fading slowly for a decade. One of the first clues to the celestial "boxing match" came in 1997 when Hubble saw a single knot in the ring shine like a bright diamond as it was first impacted by the shock wave.

1. What do the two pictures show?

The image at left, taken Feb. 2, 2000, shows the glowing gas ring around supernova 1987A. The gas, excited by light from the explosion, has been fading for a decade, but parts of it are now being heated by the collision of an invisible shock wave from the supernova explosion. In the picture on the right, image processing was used to emphasize four new bright knots of superheated gas that were discovered during the February 2000 observations. The brightest knot, at far right, was seen in 1997. Astronomers have been waiting several years to see more of the ring light up as the supernova shock wave smashes into it.

2. Did debris from the supernova explosion create the ring of material?

No. Astronomers believe the ring is made up of old gas that was ejected by the star 20,000 years ago, long before it exploded. The ring's presence was given away when it was heated by the intense burst of light from the explosion, which scientists observed in 1987. The ring has been slowly fading ever since then as the gas cools.

3. Why are Hubble's observations of this supernova significant?

Astronomers have collected more information on this supernova than any other. For the first time, astronomers watched a star in a nearby galaxy explode as a supernova and then searched archival photos of that region and identified the star that created the violent event. Since then, astronomers have been monitoring the expanding wave of debris from the explosion. Previous Hubble spectroscopic studies and radio and X-ray telescopic observations of the expanding supernova shock wave led astronomers to anticipate that the titanic collision was only a matter of time. As far back as 1992, astronomers predicted that the ring would become ablaze with light as it absorbs the full force of the crash.