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Shock Wave Sheds New Light on Fading Supernova

Don Savage
Headquarters, Washington, DC                     February 10, 1998
(Phone:  202/358-1547)

Tammy Jones
Goddard Space Flight Center, Greenbelt, MD
(Phone:  301/286-5566)

Ray Villard
Space Telescope Science Institute, Baltimore, MD
(Phone:  410/338-4514)

RELEASE:  98-24

SHOCK WAVE SHEDS NEW LIGHT ON FADING SUPERNOVA

       NASA's Hubble Space Telescope is giving astronomers a 
ringside seat to a never before seen titanic collision of an 
onrushing stellar shock wave with an eerie glowing gas ring 
encircling a nearby stellar explosion, called supernova 1987A. 

       Though the star's self-destruction was first seen nearly 11 
years ago on Feb. 23, 1987, astronomers are just now beginning to 
witness its tidal wave of energy reaching the "shoreline" of the 
immense light-year wide ring.

       Shocked by the 40-million mile per hour sledgehammer blow, 
a 100-billion mile diameter knot of gas in a piece of the ring has 
already begun to "light up," as its temperature surges from a few 
thousand degrees to a million degrees Fahrenheit. 

       "We are beginning to see the signature of the collision, 
the hammer hitting the bell. This event will allow us to validate 
ideas we have built up over the past ten years of observation," 
says Robert Kirshner of the Harvard-Smithsonian Center for 
Astrophysics (CfA) in Cambridge, MA.  "By lighting up the ring, 
the supernova is exposing its own past."

       Astronomers predict it's only a matter of years before the 
complete ring becomes ablaze with light as it absorbs the full 
force of the crash. 

       Illuminating the surrounding space like a flashlight in a 
smoky room, the glowing ring is expected to literally shed a 
brilliant new light on many unanswered mysteries of the supernova:  
What was the progenitor star? Was it a single star or binary 
system?  Are a pair of bizarre outer rings attached to an 
invisible envelope of gas connecting the entire system?

       "We have a unique opportunity to probe structure around the 
supernova and uncover new clues to the final years of the 
progenitor star before it exploded," adds Richard McCray of the 
University of Colorado in Boulder, CO.  "The initial supernova 
flash only lit up a small part of the gas that surrounds the 
supernova.  Most of it is still invisible. 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."  

       Though scientists will never solve the paradox of what 
happens when an irresistible  force meets an immovable object, the 
supernova collision is the closest real-world example yet.  "This 
supernova gives us an unprecedented opportunity  to directly 
witness new physics of shock interactions," says McCray.  "Though 
astronomers have measured shock effects from the expanding debris 
of many supernovae which are centuries-old, their impact 
velocities are at least ten times slower than the ones we see 
today in supernova 1987A." 

       The ring was formed 20,000 years before the star exploded.  
One theory is that it resulted from stellar material flung off 
into space as the progenitor star devoured a stellar companion.  
The ring's presence was given away when it was heated by the 
intense burst of light from the 1987 explosion.  The ring has been 
slowly fading ever since then as the gas cools.

       Several years ago radio waves and X-rays were detected as 
the fastest moving explosion debris slammed into cooler invisible 
gas inside the ring. In spring of 1997 the newly installed Space 
Telescope Imaging Spectrograph (STIS) first measured the speed of 
the  supernova debris pushing along the shock wave.  "The STIS 
lets you see the invisible stuff," says George Sonneborn of 
Goddard Space Flight Center in Greenbelt, MD. "We see the shock 
happening everywhere around the ring."  In July, Hubble Wide Field 
and Planetary Camera-2 images taken by Robert Kirshner and co-
investigators showed that a compact region near on the ring lit up 
like a sparking diamond set in an engagement ring. 

       Supernova 1987A is the brightest stellar explosion seen 
since Johannes Kepler observed a supernova in the year 1604. It is 
located about 167,000 light-years from Earth in the Large 
Magellanic Cloud. 

       The Space Telescope Science Institute is operated by the 
Association of Universities for Research in Astronomy, Inc., for 
NASA, under contract with the Goddard Space Flight Center, 
Greenbelt, MD.  The Hubble Space Telescope is a project of 
international cooperation between NASA and the European Space 
Agency.

                       - end -

EDITOR'S NOTE:  Images to accompany this release are available to 
news media representatives by calling the Headquarters Imaging 
Branch on 202/358-1900.
   NASA photo numbers are:     Color:  98-HC-58, 98-HC-59

The images are also available electronically through the Internet 
via World Wide Web, ftp or Gopher.  The Internet addresses are:  
ftp:      ftp.stsci.edu (IP address:  130.167.1.2)
WWW:    http://www.stsci.edu
Gopher:     www.stsci.edu