Astronomers Dumbfounded : Mystery Object May Bump Into Supernova

Astronomers here described themselves Wednesday as dumbfounded by the mysterious appearance of an interstellar object next to the recently discovered and intensely studied supernova.

The object, an apparent companion to the supernova that is on a collision course with the exploding star, appears as a bright blob of light in images taken in recent weeks at the Cerro Tololo Inter-American Observatory in Chile. It defies explanation to the point that many experts had doubted its existence.

Those doubts were laid to rest when scientists attending a joint meeting of the Canadian and American Astronomical Societies here were told Wednesday that the strange object has been confirmed by other astronomers in Australia, using a different telescope.

‘Slam Into It’

“I don’t understand what the devil it is,” mused Richard A. McCray of the University of Colorado, a lead scientist in the multiagency international effort to study the supernova. The mystery surrounding the companion object is an example of the surprises that have confronted scientists studying the supernova, discovered by Canadian astronomer Ian Shelton last February.

Some of those questions might be answered as soon as the end of the year if the supernova does what scientists expect it to do and crashes into the companion.

“The supernova is going to slam in to it,” McCray said, because the giant star’s outer shell is expanding rapidly. “That’s going to be super,” the astronomer added, sounding like a schoolboy with a new toy.

When that happens, the collision should send out showers of radiation that will tell scientists what the companion was made of and possibly allow them to deduce what it all means.

Astronomers expect the collision within the next 20 months, and perhaps by year’s end.

Peter Nisenson of the Harvard-Smithsonian Center for Astrophysics discovered the companion, which glows with a tenth of the luminosity of the supernova, while making routine pictures of the supernova with Cerro Tololo’s four-meter telescope, the largest in the Southern Hemisphere.

“We were trying to measure the diameter of the supernova” on March 25, Nisenson said. The image produced by the huge telescope surprised Nisenson when it depicted what looked like a double star.

“We didn’t know what to make of it,” Nisenson said, because there had been no star in that area of the sky. Scientists are sure of that because the supernova occurred in the Large Magellanic Cloud, a companion galaxy to the Milky Way that is one of the most intensely studied regions of the sky. If there had been anything in that area that could have been transformed into the bright spot discovered by Nisenson, it would have shown up in previous photographs.

Fierce Debate

Nisenson went back to the mountaintop in the foothills of the Chilean Andes on April 2 and photographed the same area. The mysterious companion showed up again, exactly as it had the week before.

A short time later, scientists at the Anglo-Australian Telescope in Australia turned their 3.9-meter scope on the supernova and also captured images of the companion.

Scientists debated fiercely among themselves here Wednesday over what the object could be, with most concluding that it probably is some form of dense cloud that is receiving energy and luminosity from the supernova. If that is so, it is unlike anything seen before.

The chances of the companion being another dim star exploding in the same area of the sky at the same time as the supernova are too extraordinary to be taken seriously, according to scientists who have concluded that the companion cannot be another supernova.

The companion is so far from the supernova that it takes two weeks for light to travel from one to the other, and none of the debris from the blast has traveled that far because matter travels much more slowly than light. In this case, the fastest moving particles are leaving the supernova at no faster than 10% the speed of light, scientists said. That means the first particles to reach the companion from the supernova will not get there for at least several months, McCray said.

Some scientists believe that the companion is a dark cloud of gas that could not be seen earlier and is now being energized by a narrowly focused beam of X-rays from the supernova.

Astronomers, however, were at a loss Wednesday to explain how that could happen.

Kenneth Brecher of Boston University, an expert on pulsars, stars that release enormous bursts of energy in pulses as they spin rapidly in the sky, speculated that a pulsar may be forming in the center of the supernova. He suggested that if the pulsar has already formed, and if it is emitting powerful beams of radiation in just the right direction, that would explain how energy is being transferred from the supernova to the companion.

‘Extraordinary Pulsar’

None of the other scientists in a crowded conference room here rose to embrace the suggestion, however.

“If this is a pulsar, it’s an extraordinary pulsar,” said Richard N. Manchester of the Commonwealth Scientific and Industrial Research Organization of New South Wales, who observed the companion with the Australian telescope.

For now, at least, the scientists are left with a tantalizing mystery that no one is able to explain.

Scientists will continue to study the supernova for many years because it is the first exploding star they have been able to observe from the day of the explosion.

Shelton, the young Canadian astronomer, was using “a tiny telescope” at the Las Campanas Observatory in Chile when he noticed on Feb. 24 that a tiny star appeared in an area where there had been none the night before.

That news traveled rapidly throughout the scientific world, and instruments around the globe and in space were turned toward the star.

The supernova, however, has not given up its secrets easily.

For a while scientists were not even sure which star had exploded, but that controversy has been settled. The star was a red giant known as Sanduleak-69.202, astronomers confirmed Wednesday.

Peaked May 22

The supernova continued brightening, just as scientists had predicted, but it peaked on May 22, at far below the level of luminosity that many had expected.

The luminosity of the supernova is decreasing “about 3% per day,” said Robert F. Garrison, director of the University of Toronto’s Southern Observatory.

The star is also cooling rapidly, and it has changed in color from bright blue to red.

“It’s a very red object against the gray of the Magellanic Cloud,” Garrison said.

Debris from the explosion is expanding outward in a shell that has enveloped the star’s center, hiding it from some instruments, but the debris carries with it the confirmation of many theories in astronomy.

Scientific observation of the heavy elements shooting from the star proves earlier theories that much of the universe was formed in the fiery furnaces of supernovas.