Professor Fred L. Whipple, who wrote the most widely-accepted theory on how the planets were formed, became chairman of the Department of Astronomy on Tuesday.

He succeeds Professor Donald H. Menzel, who wanted to spend more time studying the sun and its effects on the earth. Monzel will travel West this week to continue his work, but will keep his posts as professor of Astrophysics and associate director of the Harvard Observatory.

Dust-Clouds

Whipple became famous last year for his work on the Dust-Cloud Hypothesis, the modern theory on how the solar system developed. His theory has virtually replaced the older Planetary and Nebular Hypotheses, which were proved implausible several years ago.

Whipple claims that the solar system started with a sprawling system of dust particles. Light-pressure and gravity forced the system to collapse; the center condensed into the sun and the outer clouds coalesced into planets.

Meteors and the Air

His most recent work has been the study of meteors. By photographing them and studying their orbits, he has discovered that the upper regions of the atmosphere change in density during the course of a year. "Whipple's Wagon Train" is currently travelling through New Mexico collecting meteors and watching them fall.

Since 1933, he has discovered six comets, about half as many as are found in an average year.

The Sun and the Earth

Professor Menzel will move to the high-altitude observatory in Climax, Colorado, which he founded in 1940. Here he will continue his work on the corona and on the sun's effects on the earth.

Menzel, who plans to expand the whole Climax set-up, has written several the-ories on the cause of the aurora and magnetic storms. This summer he proved that a ring nebula--a ring of bright gas surrounding a star--was actually composed of huge comets.

He has also done work on how atoms emit light and how energy escapes from the sun.