The first detailed images of a supernova remnant paint vivid portraits of the leftovers of a giant exploding star.
The images released this week by two separate groups of astronomers, is of Supernova 1987-A, located some 165,000 light-years away in the Large Magellanic Cloud. They depict bright ring structures caused by fast-moving material slamming headlong into a lumbering cloud of gas emitted long ago by the same source.
The supernova was first seen exploding in 1987, allowing researchers to predict that the remnant would become visible sometime between 1995 and 2010.
A December 1999 near-infrared image of Supernova 1987-A, released this week. Red spots indicate the brightest features. The image was produced by a 4-meter telescope in Chile operated under contract with the National Science Foundation.
Making a space ring
Material ejected by the supernova is catching up with slower moving, high-density gas emitted some 20,000 years ago, long before the star blew apart, said Arlin Crotts, an astronomy professor at Columbia University. In the intervening millennia, the star emitted a very fast, low-density wind that has been sweeping the old gas ahead and sweeping out space as though with a giant cosmic broom.
"The debris from the explosion has basically been coasting through this relatively empty region," Crotts told SPACE.com. "But now it's hitting the dense stuff that was swept up."
The impact of the debris with the gas cloud produces the luminous ring, which was also imaged by the Hubble Space Telescope (see below).
Crotts said there have been various theories about how supernova remnants evolve and behave, but now researchers have actual images to study. "This is the first supernova remnant that we've seen this early on and in this detail," he said.
Some answers, lots of questions
While the images yield tantalizing details, much of what they show is not fully understood. We asked Crotts, for example, what causes the rings:
"That's a very good question," he said. "We don't really know the answer."
A few details can be teased out of the images. While the supernova expands in all directions, the expansion is not uniform, Crotts explained. And the ring, a tube-shaped structure akin to a Hula-Hoop, represents the densest area of the old gas cloud.
"The entire ring is beginning to be engulfed with shocked material from the supernova, lighting up the ejecta and circumstellar material as a supernova remnant," Crotts said, who with colleagues captured the image using a 157-inch (4-meter) telescope in Chile.
Some of the bright spots in the ring are regions closest to the supernova, but others represent areas that have been hit by faster-moving portions of the ejecta.
Another view, from Hubble
Hubble image of Supernova 1987-A shows bright features as of February 2 (left) compared with the early days of the developing ring in 1997.
A separate group of astronomers captured the same object with the Hubble Space Telescope. An early clue of the approaching fireworks came in 1997 when Hubble saw a single shining "bright diamond" indicating the shock wave was beginning to hit the old gas cloud.
"That was the opening jab," said Robert Kirshner of Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. "Now the dancing around is over and the slugfest will begin."
And the best may be yet to come, researchers say.
"The real fireworks show is finally starting, and over the next 10 years things will get spectacular," said Peter Garnavich of the University of Notre Dame. More Hubble observation time is planned for later this year.
