Hubble images stellar shockwave

Baltimore--The spaceborne astronomical tools of discovery (DN 2/2/98, p. 66) continue to unveil wonders of deep space. Recently released images taken by the Hubble Space Telescope shed new light on the brightest stellar explosion seen since Johannes Kepler beheld a supernova in the year 1604. First observed over eleven years ago, supernova 1987A is roughly 167,000 light years from Earth.

The collision of a 40 million mph outwardly expanding stellar shockwave of matter from the explosion with the inner boundary of a surrounding light-year wide disk of gas is heating and "lighting up" the material. The flaring of a 100-billion mile diameter knot of gas in the ring (see photo) is the result of temperatures soaring from a few thousand to a million degrees Fahrenheit. The propagating collision observed over the next few years will rend the gas disk and generate many X-ray and radio-wave emissions.

Such were detected years ago as the leading edge of debris ripped through the cooler, invisible gas inside the ring. Last spring, the Hubble's newly installed Ball Aerospace and Technologies Corp.(Boulder, CO) Space Telescope Imaging Spectrograph (STIS) measured the velocity of the supernova remnants pushing along the shockwave. "The STIS lets you see the invisible stuff," notes George Sonneborn, an investigator at the NASA Goddard Spaceflight Center (Greenbelt, MD), and "We see the shock happening everywhere around the ring." In July, the latest version of the Jet Propulsion Laboratory (Pasadena, CA) Wide Field and Planetary Camera captured the blossoming light from the gas knot.

"By lighting up the ring, the supernova is exposing its own past," says Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics (Cambridge, MA). The ring formed 20,000 years before the star exploded. It may have resulted from material from a progenitor binary-star system being thrown into surrounding space as the denser of the stars devoured the other which had expanded into a cool red giant. The glowing ring is expected to provide answers to such questions as well as the nature of a pair of non-concentric outer rings surrounding the system.

"We have a unique opportunity to probe structure around the supernova and uncover new clues to the final years of the progenitor star," adds Richard of the University of Colorado (Boulder, CO). "The initial supernova flash only lit up a small part of the gas that surrounded it. But the light from the crash will give us a chance to see this invisible matter for the first time, and then perhaps we can unravel the mystery of the outer rings."