Alice Waterlan, Age 13, Of Oriskany Falls, New York, for her question:

What is Halley's comet?

There is no excuse for an earthling to be bored or down hearted. Our luxury planet teems with enough wonders to enchant every day of our lives. And every night it turns to face the wonders of the starry sky. Once in a while a razzle dazzle visitor such as hal1ey's comet adds an extra wonder to the orderly parade of the heavens.

A comet is a member of the solar system, and like a planet it travels in a prescribed path around the starry sun. However, compared with a planet, a comet is a small body, and its orbit is nowhere near circular. It is a long, thin oval. One end of this ellipse makes a close u turn around the sun and the other end swings far away, often beyond the orbits of the farthest planets. Each trip may take many earth years, and the comet shines in our skies only when it loops around the sun.

Man, it seems, is a born star gazer, and through thousands of years our ancestors watched and charted the parade of heavenly bodies across the skies. Each visiting comet, with its brilliant head and trailing hair, was noted by early astronomers in Egypt and Europe and often in faraway China and Japan. These razzle dazzle visitors seemed to arrive and depart unexpectedly, until Edmund Halley proved that comets, like other members of the solar system, travel on strict schedules.

Hal1ey was a famous English astronomer of the late 17th and early 18th centuries. He scanned the old records and noticed that a bright comet had been appearing at 75 year intervals for some 2000 years. Hal1ey assumed that it was one and the same comet, traveling a long narrow orbit around the sun. He predicted its return around Christmas in the year 1778. Halley's comet appeared on schedule, though the famous astronomer did not live to see it. The dazzling visitor, bright enough to be seen at noon, appeared in 1910.

A comet is a bulky bundle of dead and frozen materials, and it shines only when it comes c1ose enough to borrow the glory of the sun. In 1910 after its swift u turn around the sun, halley's comet s1awed dawn on its path to the edge of the solar system. In 1950 it completed the u turn at the opposite end of its orbit, far beyond the orbit of Neptune. It is now on its way back for a return visit to the sun. In 1985 the famous comet is expected to show its brilliant head and spread its golden tail across our skies once again.

In the past 200 years astronomers have checked and charted the schedules of many brilliant comets. Recently they noticed that hal1ey's comet appeared in the skies of the midd1e east near the time the Christian era began. The most famous of all comets indeed may have been the star of Bethlehem.