A photograph of Halley's Comet that appeared on Page A1 Friday was incorrectly identified by the Associated Press as having been taken by Vega-1, the Soviet spacecraft. The picture actually was taken through a telescope in 1910. It was computer-enhanced with color and shown Thursday on British television, from which it was copied by the AP, which misinterpreted the commentary about comet photos being shown on the television program.
Halley's Comet, the legendary celestial object circling past the Earth since the origin of the solar system, flashed into close-up view today for the first time.
Photographs from the Soviet Vega 1 spacecraft, orbiting within 5,400 miles of the comet's head, appeared on television screens at a Soviet space center this morning before a cheering crowd of scientists from many nations. Photometric patterns shifted on the screen as a bright yellow core came into focus, the first close look at the great glowing ice ball that scientists had deduced was there.
"The size looks about three to four kilometers," or about two miles, droned the commentator. "Evidently, it is the nucleus."
For the scientists here, that initial confirmation was one of the morning's most important events, to be followed by more tantalizing clues about the size and density of dust particles being blown off from the icy nucleus and frequency of waves of highly charged atomic particles.
Although the dust particles closer to the comet were finer and less dense than expected, the spacecraft ran into a heavy jet of dust gushing from the comet 25 minutes after it swung in for its close-up.
This jet has raised several questions, which scientists said would take several days to decipher. Evidence collected in upcoming fly-bys is expected to help clarify the issue.
Soviet, American and European scientists who commented here were unanimous in declaring the Vega 1 probe a major achievement, and in noting that its findings indicate success for follow-up missions -- by a Vega II on Sunday and by the European Space Agency's Giotto, which is to come within 350 miles of the comet next Thursday.
Two Japanese spacecraft, also launched in the last 15 months, are to approach the comet on Saturday and Monday. In all, there are eight probes, none American. A U.S. mission was scrapped as too expensive.
The historic lure of the comet's fly-by of Earth every 76 years clearly is not only romantic. The ambitious multinational Halley project aims to peer into the comet's core, photograph it -- a major task of the Giotto mission -- and analyze its elements, some of which are thought to date back to the beginning of the solar system.
"Not only is it a messenger from distant places, but it is a messenger from the distant past," said Soviet scientist and project leader V. M. Kovtunenko at a press conference today. "There is no other matter that old" that scientists have been able to analyze, he said.
For Fred Whipple, 79, an American astronomer who in 1950 came up with the "dirty snowball" theory of comets containing discrete nuclei, today's preliminary finding of a nucleus was the key piece of news.
"It is the first clear-cut evidence of a nucleus," said Whipple, of the Smithsonian Astrophysical Observatory in Cambridge, Mass., a member of the International Halley's Watch group. "I would say it is a huge success, huge."
The dirty-snowball theory has been accepted for years, and considerable indirect evidence for it has been built up. But today's confrontation showed the nucleus in dramatic full-frontal detail.
Comets are among the most unusual objects in the solar system and are believed to be at least as old as the solar system -- 4.5 billion years. They may have been formed as debris left over from the creation of the solar system.
Despite their appearance as burning stars with fiery tails, comets are believed to be made mainly of primordial ice embedded with dust-sized bits of rock. Yesterday's meeting between machine and comet appeared to confirm this theory.
When Halley's Comet is far from the sun, it is merely a cold body racing silently through the dark vacuum of space.
It is only when it approaches the sun that it begins to light up. The "solar wind," the great stream of radiation pouring out from the sun, vaporizes some of the comet's surface, creating a large "coma" or glowing gas-and-dust cloud around the ice ball. Most of the dust shoots in a jet away from the sun, and is illuminated by the sun's light. This is the comet's tail.
The Vega mission, launched Dec. 15, 1984, was six years in the making. It carries equipment and experiments from Western and Eastern Europe as well as one from the United States.
This international character was apparent in a high-ceilinged room at the institute, where scientists squeezed between computers were speaking different languages but poring over early printouts that evidently needed no translation.
The Vega vehicle was built by Czechoslovaks. The French perfected the optics for the camera. Hungarians play a major role in data collection, while Poland has an experiment on low-frequency plasma waves.
John Simpson, a physics professor at the Enrico Fermi Institute at the University of Chicago, was the lone American to participate, experimenting with a dust counter and mass analyzer.
"One of the most fascinating aspects is the international," said Gerhard Umlauft, of the Max Planck Institute in Lindau, West Germany, who worked with neutral gas instruments and data collecting.
The three-hour data transmission of about 500 pictures, received with a nine-minute delay over a distance of about 105 million miles, provided scientists with information that could elucidate the origin of comets by determining their makeup in detail.
Furthermore, because comets are believed to have been formed in the creation of the solar system, their composition may tell a good deal about the making of that as well, a kind of ghostly flying remnant of the system's initiation.
"No question that this is a major step in our understanding of comets," said American scientist Carl Sagan. "There was first-class data, about charged particles, about dust spewing off the comet. This will help us to understand the nature of comets, and as soon as we understand that, we will understand something about their origins."
To welcome the visiting delegations, the Soviet Space Research Institute -- traditionally a closed facility -- allowed journalists and scientists to walk the corridors and even inspect experiments.
"They really have something to be proud of and they want to show it off," said Burton Edelson, assistant administrator for space science at the National Aeronautics and Space Agency, who was here as part of the American delegation.
The Vega 1 mission, launched in December 1984, began with a probe of Venus last June. It has been followed by Vega 2, an identical spacecraft which will pass by the comet at closer range on Sunday to analyze the comet's coma.
The success of Vega 1 had immediate reverberations in the international scientific community, marking one of the Soviets' bigger public relations coups since the days of Sputnik. The Soviets' other major space effort, aimed at establishing a permanently manned space station, has had less of an impact.
Scientists were relieved to find that dust particles surrounding the comet were finer and less dense than some had feared. There had been concern that Giotto, passing within the comet's great dusty shroud, the coma, would be fatally bombarded by heavy particles as it swung to within 350 miles of the nucleus. Giotto will be traveling through the coma -- which is thousands of miles across -- at a relative speed of 150,000 miles per hour. At that speed, small rocks and even dust are destructive.
"This suggests that Giotto will not be mutilated," noted Sagan. "There was a real chance of a kamikaze mission on that one. Now it looks hopeful that Giotto will come that close."