Onset of Titanic Collision Lights Up Supernova Ring

Donald Savage
Headquarters, Washington, DC
Feb. 16, 2000
(Phone: 202/358-1547)

Nancy Neal
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-0034)

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

RELEASE: 00-27

ONSET OF TITANIC COLLISION LIGHTS UP SUPERNOVA RING

NASA’s Hubble Space Telescope is giving astronomers a
ringside seat to a never-before-seen, violent, celestial
“main attraction” unfolding in a galaxy 169,000 light years
away. The knockout event is the collision of the fastest
moving debris from an immense stellar explosion seen in
February 1987 with the gas ring that circles that site.

This collision is beginning to cause the gases in the
ring 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. In new pictures taken on February 2,
Hubble’s sharp view revealed four bright new knots of heated
gas at places that had been fading slowly for a decade.
Under an observing program called the supernova intensive
survey, a team of astronomers has been monitoring SN1987A
with Hubble since it was launched in 1990.

One of the first clues to the celestial fireworks came in
1997 when Hubble saw a single knot in the ring shine like a
bright diamond as it was first impacted by the shockwave.
“That was the opening jab. Now the dancing around is over
and the slugfest will begin,” says Robert Kirshner of
Harvard-Smithsonian Center for Astrophysics in Cambridge, MA.

“The real fireworks show is finally starting and over the
next ten years things will get spectacular. It helps that
Hubble is giving us an unparalleled view,” adds Peter
Garnavich of the University of Notre Dame.

Previous Hubble spectroscopic observations, and radio and
x-ray telescopic observations of the expanding supernova
shockwave all 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.

Upon seeing the new Hubble pictures, Kirshner remarked,
“It’s about time. We saw that first hotspot two years ago,
but I was getting nervous that we might have been mistaken
about its location. It’s great to see the shock wave start
to light up the ring.”

The supernova, called SN 1987A, has long puzzled
astronomers. They 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 1987 explosion.
The ring has been slowly fading ever since then as the gas
cools.

The initial supernova flash only lit up a small part of
the gas that surrounds the supernova. Much of it is still
invisible. But the light from the crash should illuminate
this invisible matter for the first time, and help unravel
the mystery of a pair of outer rings seen around the
supernova as well.

“Now as the central ring begins to light up again, we can
see how this old material is arranged around the star. We can
map its distribution,” Kirshner says. “This event gives us
another chance to see the true structure of the gas around
the supernova and to puzzle out how it got there.”

Kirshner and colleagues plans to use Hubble to do follow-
up observations later this year to track the ongoing drama of
one of the biggest celestial collisions ever witnessed by
astronomers.

The Supernova Intensive Survey team includes Dick McCray,
University of Colorado, Boulder; Nino Panagia, Space
Telescope Science Institute, Baltimore, MD; Nick Suntzeff,
Cerro Tololo Inter-American Observatory, Chile; and George
Sonneborn and Jason Pun, NASA Goddard Space Flight Center,
Greenbelt, MD.

Images: http://www.stsci.edu