Comet of the Century

Even now it is hurtling closer, racing toward a year-end rendezvous with the sun. By December it will be the brightest object in the predawn sky, providing early risers with an unusual celestial display. The newly discovered comet may eventually be 50 times as brilliant as Halley's comet, which last dazzled the world in 1910; its tail could arc across some 30DEG--or one-sixth--of the evening sky. With no effort at hyperbole, Harvard Astronomer Fred Whipple says the onrushing giant "may well be the comet of the century."

The great comet was discovered in March by Czech-born Astronomer Lubos Kohoutek while he was looking for asteroids with the Hamburg Observatory's 31-in. Schmidt telescope; at that time it was some 480 million miles away from the sun, or roughly in the vicinity of the orbit of Jupiter. In contrast, Halley's comet--less bright than Kohoutek's--was not spotted until it was about 170 million miles closer to the sun. Although the nucleus of a typical comet (which is thought to be composed of frozen water, methane and ammonia, as well as dust particles) is only about a mile in diameter, Kohoutek's comet seems to be a brobdingnagian 10 to 15 miles across. Moreover it will come to within 13 million miles of the sun. That relatively close flyby should produce a dazzling interaction between sun and comet.

Although the comet is now visible only as a speck of light in telescopes, solar radiation will boil off gases and dust from the nucleus as it approaches closer to the sun. In the "solar wind," the stream of electrically charged particles that continually emanate from the sun, the material from the nucleus should be swept into the characteristic comet's tail. As it reacts with the charged particles, the tail should begin to glow brightly--so brightly, in fact, that Brian Marsden of the Smithsonian Astrophysical Observatory believes that the comet could be visible to the naked eye in daylight just before its close approach to the sun in December, and even more spectacularly in the evening during January as it begins to move away. Perhaps the most remarkable sight will be seen by observers in Latin America. On the day before Christmas, an annular eclipse* will occur over South America. That should create an awesome Yuletide display: a fiery ring of sunlight, the Comet Kohoutek and the bright planets Jupiter and Venus, all grouped in the same area of the eclipse-darkened sky.

Hundreds of observers around the world are preparing to examine the comet in many frequencies of light --from ultraviolet to infrared. Harvard's A. Edward Lilley even hopes to detect, for the first time, microwave emissions from a comet. Above the earth's obscuring blanket of air unmanned satellites--perhaps even Skylab's sophisticated observatory--may make the most fruitful observations of all. All the observations will be aimed at determining the structure of the comet and its origin--probably beyond the planet Pluto, where billions of comet-like objects are believed to be orbiting as remnants from the solar system's creation.

* Which occurs when the moon, at one of its more distant points from the earth in its elliptical orbit (when it appears slightly smaller in the sky), eclipses all or the sun except a glowing outer rim.

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