Outbreak of Comet Fever

Close encounter with a surprise visitor from deep space

To ancient stargazers, comets (from the Greek for hairy star) were signs of heavenly displeasure. Actually, they are stray bits of debris, largely ice and dust, left over from the formation of the sun and its family of planets nearly 5 billion years ago. Skywatchers around the world got a rare chance last week to view such a dirty celestial snowball close up, at least by astronomical standards. The surprise visitor from deep space swept to within 2.9 million miles of earth, the nearest approach by a comet in two centuries.

Like all comets, the interloper was named for its discoverers. On April 25 it was detected by the new U.S.-British-Dutch Infrared Astronomical Satellite IRAS. But the scientists were unaware of a rule requiring notification of the International Astronomical Union's central bureau of telegrams in Cambridge, Mass. Several days later, two dedicated amateur comet hunters, Genichi Araki, 28, a junior high school teacher in rural Japan, and George Alcock, 70, a retired teacher in Britain who has spotted three other new comets, identified the hazy blob in the sky and properly reported it. The astronomical establishment diplomatically honored all three claims by calling the comet IRAS-Araki-Alcock.

For American astronomers, who are still deeply disappointed by the failure of the U.S. to send off a probe to intercept the most famous comet of all, Halley's, when it returns in 1986, IRAS-Araki-Alcock was a gift from heaven. At close encounter, it appeared as a blurry patch, about three times the diameter of the full moon, near the bowl of the Big Dipper.

Even sharp-eyed amateurs with small telescopes or binoculars could make out the comet's bright central mass, or nucleus, and its long gaseous tail. Astronomers concluded that I-A-A was probably not a "virginal" comet, meaning one that has never before swept around the sun. Its lack of brilliance suggested that the sun had boiled off some of its icy material on earlier journeys, hundreds or even thousands of years ago.

Like most comets, I-A-A contains molecules of ammonia and nitrogen, along with water, presumed building blocks of the solar system. But another satellite, the International Ultraviolet Explorer, also found surprising indications of sulfur molecules. Said University of Maryland Astronomer Michael A'Hearn: "The sulfur may be one of the few things we see that actually reside in the comet's nucleus." The most stunning observational feat came when the big, 1,000-ft. radio telescope in Arecibo, PR., managed to bounce radar waves off the fleeting object and perhaps settled the old argument over whether cometary nuclei are gaseous or solid. Said Harvard's Fred Whipple, dean of American comet watchers and chief proponent of the dirty-snowball theory: "The radar proves to my satisfaction that there is a solid object in the center of the comet."

The most elated observer was undoubtedly Araki, who regularly scans the skies over his village in Niigata prefecture. "I've discovered a wonderful star," said the young bachelor. "Now I've got to discover a wonderful wife." Perhaps the comet was a propitious sign. This file is automatically generated by a robot program, so viewer discretion is required.