In 1572 Tycho saw a bright light in the northern sky in the constellation Cassiopeia. He believed he was witnessing the birth of a new star, a nova stella. He was mistaken. Forty years later, in 1612, Simon Marius saw the supernova shine again. This time, the supernova was not nearly as bright as it previously was. In fact, it may not have been noticed if telescopes had not been invented a few years before.
On February 24, 1987, another supernova burst back into the astronomical world as a brilliant light. Sanduleak -69 degrees 202 had finally come to an end, resulting in an explosion called Supernova 1987A. What is left of the original star shines much more dimly than it ever has. Astronomers believe that the supernova will revive, shining brightly once more.
When a supernova explodes, it leaves only a small, dense core, and usually nothing remains to rise from the dead.
Can we trust the records of the life of Supernova 1987A? The Chinese have ancient chronicles telling of more than one appearance in Cassiopeia. The Chinese sometimes embellished eyewitness accounts to provide astrological support for the royalties' adventures. The reappearance of this supernova, according to Lawrence Marschall, could be, "no more substantial than sightings of Elvis in supermarket tabloids."
Even if Supernova 1987A does arise again, what would be its source of light?
If the supernova does rise from the galaxy graveyard, astronomers believe the light will not come from the star that exploded, but from a shell of debris the star ejected into space. After the explosion in February 1987, most of the star's mass was shot into space at incredibly high speeds-one tenth the speed of light. The material is still on its outrushing path today.
Over 100,000 years, the debris would normally thin out and dissipate. It can't, however, for the debris is racing toward another cloud of material the star ejected before its final explosion. When the material from the explosion hits the already existing debris, 1987A is expected to shine again. When will it be reborn? We may see 1987A shining again in 3 to 5 years.
Photo. Remnants of a Supernova. Captured in a brilliant Hubble photograph, these supernova remains are an example of the spectacularly colored scenes captured by the Space Telescope. Courtesy J. Morse/Space Telescope Science Institute, NASA.
Hubble may also have evidence that the supernova's debris may collide with the supernova itself and may even explode again.
The Space Telescope took pictures of the supernova in late 1990 and again, after it was repaired, in February 1994. It discovered rings around the supernova. This ring is about 1 light year away from the supernova and consists of material thrown off the star before it exploded. The photo only shows the brightest part of the ring, so scientists don't know for sure how thick the ring really is, or how far it extends.
Scientists do know that the cloud of debris shot out during the explosion will hit the ring in the mid-1990s. The collision may be slow, like the slow-motion impact of two colliding trains, or it may occur in one large explosion. The reborn supernova will appear as a tiny spot of light, and only telescopes like Hubble will be able to see any detail.
Photo. Supernova 1987A's rings. The bright ring in the center of the photograph contains the supernova itself and the two dimmer rings are on either side of it. The rings do not actually intersect, as they appear to, because they are in three separate planes. Based on low-resolution ground pictures, astronomers had expected to see an hourglass-shaped "bubble" of gas enveloping the supernova and were surprised to find that there were two large, dim rings instead. A possible explanation for the discrepancy is that "high energy radiation" is covering the area within the two rings and registering on the other images. This is one of our favorite Hubble images of all time and made the Space Telescope Science Institute's HST Greatest Hits 1990-1995 Gallery -- a collection of the most popular HST pictures available for download. Courtesy Dr. Christopher Burrows, ESA/STSCI and NASA.
The supernova that has lived forever will die with a final performance for which it is certainly worth waiting.
