An astronomer, Whipple helped figure out the orbit of a newly discovered planet: Pluto. During World War II Whipple helped develop “chaff” — flakes of metal designed to be dropped from planes to fool enemy radar.
After the war, as director of the Smithsonian Astrophysical Observatory in 1955, he correctly predicted that the age of artificial satellites was imminent, and set up a globe-spanning network of amateur astronomers to monitor them. They were ready when Russia’s Sputnik was launched in 1957, and were able to track it as it orbited.
But Whipple is best known as the researcher who correctly figured out that comets are “dirty snowballs,” which was proven by a probe to Halley’s comet in 1986. “Fred Whipple was one of those rare individuals who affected our lives in many ways,” says Charles Alcock, director of the Harvard-Smithsonian Center for Astrophysics. Whipple never tired of comets: at 95, he came out of retirement to work as a researcher for NASA’s Comet Nucleus Tour, a probe to study comets. The probe was lost shortly after launch in 2002. Whipple died August 30 at age 97.