Fred Whipple; professor was leading authority on comets

Fred Lawrence Whipple, considered the world's foremost authority on comets, died Monday in Cambridge. He was 97.

For more than seven decades, Dr. Whipple worked at Harvard University and the Smithsonian Astrophysical Observatory, which he helped move to Cambridge from Washington, D.C. From his observations, his research, his inventions, and his enthusiasm for determining how things work, the picture of the heavens became much clearer to astronomers and lay folks alike.

''He's the grand old man of comets," Carolyn Shoemaker told The Boston Globe in 1996. Shoemaker, with her husband, Eugene, discovered more than 30 comets. ''He's my hero," her husband added. ''Our relationship is that of hero and acolyte."

Before Dr. Whipple's work, astronomers thought of comets as loose collections of dust and vapor packed into a missile through gravity. In 1950, he argued otherwise.

''The older theory was nonsense," he told the Globe decades later.

A comet, he said, consists of ''a dirty snowball" of ice, ammonia, methane, and carbon dioxide as its core, with a gossamer tail of particles that broke off from the core.

His conceptual leap, said Brian G. Marsden of the Harvard-Smithsonian Center, ''was one of the most important contributions to solar system studies" in the 20th century.

His research also helped detail the behavior and motion of a comet. As a comet approaches the sun, he said, the star's heat would turn part of the comet's icy core into jets of explosive vapors, which, in turn, would propel the comet along its trajectory.

The explanation made it easier to track comets and predict their paths. Later, photographs of Halley's Comet proved the theories of Dr. Whipple.

Dr. Whipple's contributions extended beyond conjecture on comets. He has been credited, for example, with determining that the source of meteors is our solar system, not far-flung stars.

He also was a leading proponent of the theory that life on Earth came from comets --embedded with the building blocks of life -- that crashed onto a barren landscape. ''If there weren't comets, we wouldn't exist," he said.

Yet many of his contributions went beyond theory and had direct practical benefits:

During World War II, the Harvard research group he oversaw took a simple solution to a deadly problem: how German radar stations tracked and targeted Allied bombers. His solution was to cut large sheets of aluminum foil into tiny slices, which the bombers would drop as they approached the radar stations. The result, of what we know today as ''chaff," was confusion and misreadings by the radar.

He created one of the world's premier observatories, the Multiple Mirror Telescope in Arizona. In the process, he conceived of a new type of telescope that used six large mirrors to focus the light into a single camera, magnifying the telescope's capabilities.

He was credited with creating the first space telescope, the Orbiting Astronomical Observatory, which was launched in 1968. Beset by a mechanical malfunction, the telescope nonetheless led the way for the Hubble Space Telescope and the Chandra X-ray Observatory. ''Fred had the vision very early about a telescope in space," Eugene Shoemaker said. ''He was talking about this before there was a NASA."

A decade before the first launch of a satellite, he invented a device that shields spacecrafts from meteors and other interplanetary projectiles. Dubbed ''the Whipple shield," these bumpers are thin layers of metal that are placed a few inches out from the spacecraft's hull and they absorb most of an impact of the striking junk. The shield, which he created in 1946, is still used by virtually every spacecraft and satellite.

''I'm an engineer at heart," Dr. Whipple said. ''I've been able to judge what instruments will work and what can be built. That's been the secret to my success."

The man fellow rocket scientists dubbed ''Doctor Comet" grew up on a farm in Iowa. As a teenager, he moved to California with his family, working as a clerk in his father's grocery store.

He majored in mathematics and received his degree in that field from the University of California at Los Angeles before declaring that math was too boring. Astronomy, for him, held more than one world of possibilities.

His background in math and logarithms, however, served as the foundation for his work finding, tracking, and predicting the path of comets.

In 1931, after earning a doctorate from the University of California at Berkeley, he came East to Cambridge, becoming the program director for the Harvard College Observatory. He began teaching at Harvard University the following year.

In 1955, he was named director of the Smithsonian Astrophysical Observatory, a position he held until 1973, when it was merged with the Harvard College Observatory to create the Harvard-Smithsonian Center for Astrophysics. In large part due to his vigor and talent, the center is today considered one of the world's top places for astronomical research.

Although he formally retired from Harvard in 1977, he continued his research at the astrophysics center. Until a few years ago, he would daily ride his bike the 3 miles from his home in Belmont to the center's offices.

Dr. Whipple leaves his wife, Babette; a son, Earle; and two daughters, Sandra and Laura.