Astronomers are used to finding all kinds of wild things in outer space -- black holes, colliding galaxies, stars spinning hundreds of times a second, even a 21-piece comet now on its way to smashing into Jupiter. Still, the giant glowing hoops that showed up in a Hubble Space Telescope picture released last week prompted veteran sky watchers to chatter like awestruck kids. "It's bizarre," said Christopher Burrows of the Space Telescope Science Institute in Baltimore, Maryland. "It's the neatest thing I've ever seen."
It's also among the most puzzling. Two huge hoops -- each a few light-years in diameter -- and a brighter, smaller ring are surrounding the site of a supernova, an exploding star whose violent death was recorded by astronomers in 1987. For millenniums before the blast, Burrows and his colleagues believe, the terminally ill star had been gushing out great volumes of gas, which formed an hourglass-shape "bubble." (The bubble would ordinarily have been spherical, except that the gas around its equator was especially thick and slow-moving and thus stayed relatively close to the supernova.) Then, when the star blew up, the flash of light made the gas glow. Most of the bubble is shining too faintly to be seen at all, but the small central ring is made of dense gas that is unusually bright.
Burrows is less confident about his explanation for the fainter, outer hoops: right next to the shining supernova is a very faint object that may be a tightly compacted neutron star, the remains of an earlier supernova explosion. If so, it could, like other neutron stars, be spewing out twin beams of fast-moving particles. The particles, slamming into the hourglass- shape gas cloud, could have created rings that glowed more brightly after the more recent supernova went off.
Other astronomers aren't entirely convinced by this hypothesis, and Burrows admits that he's "going to have to keep watching it for a while to figure out what is really going on." Whether he is right or wrong, studies of the rings could eventually provide important clues about how stars die. One thing for sure: these stellar performers can go out with bangs that leave brilliant and lasting marks on the cosmos.