VANCOUVER -- The exploding star, or supernova, in the skies of the Southern Hemisphere peaked in brightness on May 22, but there are hints that surprises and cosmic fireworks are ahead, including a collision with the enigmatic stranger apparently traveling with it.

The most intriguing puzzle connected with the supernova is the discovery of the inexplicably bright companion -- separated from the explosion by less than two light-weeks -- and the question of what will happen when the exploding shell of the supernova smacks into it in an estimated five to 15 months.

A roomful of astronomers at a joint meeting of the American and Canadian Astronomical Societies here at the University of British Columbia last week, including one of those who first discovered the mysterious companion, agreed on little other than that they have can come up with "no plausible explanation" for such an object.

Among the other findings revealed at the meeting is that the supernova also seems to have a continuing source of power hidden at its core, a characteristic that would account for some of its unexpected behavior. This internal engine may restore the supernova to an even greater brilliance in X-ray, gamma ray and ultraviolet wave lengths.

Or dust from the cataclysmic demise of Supernova 1987A -- generally considered one of the most stunning events in modern astronomy -- may, starting in the fall, blot out its light for anywhere from six months to seven years.

The supernova, about 170,000 light-years away, is the closest to Earth in nearly 400 years and offers astronomers an unusual chance to study the processes that forge worlds and life.

The unexplained companion is one-tenth as bright as the supernova and much brighter than any other known body in the Large Magellanic Cloud, the galaxy where the explosion occurred. Since no such object was observed in this heavily studied region before the explosion, astronomers concluded it must be a product of the cataclysm.

It is unlikely that it is a huge dust cloud that is reflecting light from the supernova, astronomers said, because it would have to be enormous even by astronomical standards, and such a cloud should not have survived so near the high-energy blue supergiant star Sanduleak-69 202 that blew up.

"While there are many other more exotic possibilities to explain these results, it is clear that more data is needed to sort them out," said Peter Nisenson, who is on the team from the Harvard-Smithsonian Center for Astrophysics that discovered the strange companion.

They made their baffling find when they examined the results of observations made at Cerro Tololo Inter-American Observatory in Chile on the four-meter telescope, March 25 and April 2, using a technique known as speckle interferometry.

The technique is designed to stop stars from "dancing" or twinkling because of atmospheric distortions. It is used to measure very small angles or distances. But the data must go through complex computer processing before it can be analyzed, so the discovery followed the initial observations by several weeks.

On April 22, their findings were confirmed by observers from the Imperial College in London using a telescope in Australia.

The Harvard-Smithsonian team took additional observations and more are planned for July, but they said they have been delayed in processing it by mechanical snafus such as the breakdown of the disc-drive on the "obsolete" computer they are using.

"If it is an object," said Richard McCray, of the University of Colorado Joint Institute for Laboratory Astrophysics, "this supernova will slam into it in five to 15 months and that will be really exciting."

That "first strike," as he put it, when shockwaves of material traveling about 1/20th the speed of light -- fast enough to go from Sun to Earth in three hours -- reach the companion, should trigger "a blaze of X-rays and gamma rays and ultraviolet rays" and should also be visible in normal light, he said.

"But right now it's theoretically impossible, which speaks mainly for our failure as theorists to explain it," he added.

There is general agreement that some source of continuing power inside the supernova caused its pattern of dimming slightly and then brightening slowly until late May.

McCray predicted that, as the explosive shell thins, there will be "leaks" of X-rays, gamma rays and ultraviolet rays. If there is a pulsar, the supernova could become one of the brightest X-ray sources in the sky in a decade, he said.

However, astronomers from the University of Minnesota and Goddard Space Flight Center in Greenbelt suggested that dust may form in the material ejected in the explosion, blocking any visible and ultraviolet light emitted by such a pulsar.

The dust would radiate energy from the pulsar in infrared wave lengths. If detected, this would constitute the first observation of dust formation in a supernova explosion. "We think the heavy elements of our bodies are formed from the dust from supernova explosions," said Bob Gehrz, of the University of Minnesota. "If we don't see dust, it will be something else we have to explain away."