One of the most spectacular astronomical sights of the century will take place Oct. 21 when a newly discovered comet passes close to the sun. Officials at the Smithsonian astrophysical Observatory in Cambridge made the announcement yesterday.

Dr. Fred L. Whipple, Director of the observatory, was the first to recognize that the object is a member of a family of comets whose orbits pass quite near the sun, where they develop long tails and become extremely bright.

Comet Now Visible

The comet is now just visible without a telescope as a fuzzy glow in the morning sky before dawn, Each day for the next several weeks it will become a little brighter and love a little nearer the sun.

the most interesting moment will come on the night of Oct. 20 when the comet will skim by the sun's surface, perhaps as close as 300,000 miles (the sun's diameter is 900,000 miles). Owen J. Gingerich, lecturer on Astronomy, and Brian Marsden of the SAO expect the total brightness of the comet may then, rival that of the crescent moon, and its tail may extend more than half-way from the horizon to the zenith.

Some Have Disintegrated

Strauge things often happen to comets when they pass close to the sun. In 1846 a comet split into two pieces in a latter of days. In 1744 a comet emerged from behind the sun with five talis where one had been before. And in 1843 comet was visible in broad daylight: While about half a dozen comets are discovered in an average year, spectacular ones such as these come very rarely.

Comets are named for their discoverers, and this one is comet Ikeya-Seki, found by two Japanese amateur astronomers. Such "comet hunters," attempting to immortalize themselves, find one comet in about 200 hours of searching.