Fred Whipple, one of the founding fathers of planetary science, died on August 30, 2004 just two months shy of his 98th birthday. The breadth of Fred's published research from 1927 through 2000 is quite extraordinary. Although his collected works were published in two massive volumes in 1972, shortly before his retirement, Fred's research contributions continued for another three decades - and another volume is planned.
Fred Lawrence Whipple was born on November 5, 1906 on a farm in Red Oak Iowa. His parents were Harry Lawrence and Celestia (MacFarl) Whipple. At the age of fifteen, the Whipple family moved to California where Fred studied mathematics at Occidental College and the University of California at Los Angeles. As a graduate student at the University of California at Berkeley in 1930, he was one of the first to compute an orbit for the newly discovered planet Pluto. Upon receiving his PhD in 1931, he joined the staff of the Harvard College Observatory. He was Chairman of the Harvard Department of Astronomy (1949 - 1956), Director or the Smithsonian Astrophysical Observatory (1955 - 1973), Phillips Professor of Astronomy (1968 - 1977) and Emeritus Phillips Professor of astronomy (1977 - 2004). In 1928 he married Dorothy Woods and their son, Earle Raymond, survives him. The marriage ended in divorce in 1935. Eleven years later, he married Babette F. Samelson and she too survives him, as do their two daughters Laura and (Dorothy) Sandra.
Shortly after arriving at Harvard in the early 1930's, Fred developed a photographic tracking network to determine meteor trajectories from simultaneous observations from two or more stations. The photographic trails, chopped by a rotating shutter, allowed their orbits in space to be determined accurately. With the strong involvement of Richard McCrosky and others, he concluded in the early 1960's that most of these meteors were on comet-like orbits and less than 1% of the naked eye, sporadic meteors could be traced to an origin outside the solar system. To fill the daytime gap when meteors could not be photographed, Fred organized a program for the radio detection of these objects. With the launch of Sputnik in October 1957, Whipple's visual network of amateur astronomers (Moon watch) was already in place to follow its progress and later on he developed an optical tracking system for meteors and artificial satellites using wide field, Baker-Nunn cameras. This latter system proved so successful that the precision tracking of these satellites could be used to model the Earth's shape and density variations from the observed gravitational effects upon these satellite orbits. He once noted that the highlight of his career was having his family and parents present at the White House while he received the President's Award for Distinguished Public Service from John F. Kennedy for this work.
His seminal works in 1950-51 on the icy conglomerate model for the cometary nucleus prompted a complete paradigm switch. Until then, the current consensus model for a comet was a flying cloud of particles; it had been so since the second half of the nineteenth century when comets were identified with meteor showers. He envisaged the cometary nucleus as a conglomerate of ices (mostly water, ammonia, methane, carbon dioxide and carbon monoxide ices) embedded within, and covered over with, a nonvolatile matrix of meteoric material. Part of his rationale for developing this "dirty snowball" model for the cometary nucleus was to provide an explanation of the so-called nongravitational forces acting upon comets. The rocket-like thrusting of a comet when the ices vaporize near the sun introduced a small, but noticeable, thrust on the comet itself and when this effect was properly modeled, the motions of active comets could be predicted far more accurately. Subsequent spacecraft ultraviolet observations showing enormous cometary hydrogen atmospheres confirmed that the major cometary ice was likely to be water. The 1986 Giotto spacecraft images, revealing a solid cometary nucleus (albeit far blacker than most had predicted), were a dramatic confirmation of Whipple's model -- though in truth few really expected otherwise at the time.
In 1942-1946, he led an effort to develop and implement strips of reflective aluminum (i.e., chaff) to confuse enemy radars in World War II. In 1948, he received a certificate of merit for this work from President Harry S. Truman. Eleven years before the launch of the first artificial satellite in 1957, he developed what is now generally termed the Whipple Shield; a thin outer metallic layer stands out from a spacecraft and protects it from high-speed interplanetary dust particles. While particles hitting this outside thin layer would penetrate, they would also vaporize, and in so doing, the resultant debris would disperse and lack the energy to penetrate the main spacecraft skin. This design was used to successfully protect the Stardust spacecraft from cometary dust particles when the spacecraft flew rapidly past comet Tempel 1 in January 2004. He also made significant contributions to fields as diverse as meteor astronomy, satellite tracking, variable stars, supernovae, stellar evolution, astronomical instrumentation and radio astronomy. Along with his colleagues Willy Ley, Wernher von Braun and others, Fred wrote and consulted for a series of very popular articles in Collier's magazine in the early 1950's and these articles, along with earlier lectures at New York's Hayden Planetarium, helped spark the U.S. involvement in space exploration. Of these early beginnings of space exploration, Fred wrote in 1972 "it was no easy task to convince people that man could really go into empty space beyond the Earth's atmosphere, and even beyond the Earth's tenacious gravitational grasp. On looking back over these years, I am still surprised that we succeeded in convincing them."
Fred was responsible for initiating the Smithsonian Astrophysical Observatory's observatory on Mt. Hopkins near Tucson Arizona and he was active in the design of the multi-mirror telescope that was in operation until 1999, when a 6.5-meter single mirror telescope replaced it. In 1981, the observatory was renamed the Fred Lawrence Whipple Observatory. Fred was successful as both a manager of large science enterprises and as a researcher. He once told me that one of his secrets for doing both management and science simultaneously involved his spending some mornings in a room adjacent to his office doing research. His secretary was asked to (correctly) notify morning callers that Dr. Whipple was not in his office at the moment and could he return the call later on in the day. When asked the secret of his longevity at his 90th birthday party, he noted, "you've got to start early." Fortunately for Planetary Science, he did start early - and he stayed late. Until he reached 90 years of age, he rode his bicycle to the office most every day and those days when he drove to work, his car was easy to identify from the single word "comets" on his license plate.
Fred Whipple was awarded seven honorary degrees and included among his many tributes are a certificate of Merit from President Truman (1948), the J. Lawrence Smith Medal of the National Academy of Sciences (1949), a Distinguished Federal Civilian Service Award (1963), the Frederick C. Leonard Memorial Medal of the Meteoritical Society (1970), the Gold Medal of the Royal Society (1983), the Bruce Medal of the Astronomical Society of the Pacific (1986), and the Henry Norris Russell Lectureship of the American Astronomical Society (1987). He also discovered six new comets and discovered and named an asteroid (1252 Celestia) after his mother. Asteroid 1940 was renamed (1940) Whipple to honor his professional achievements.
Fred Whipple was a Harvard Professor, director of the Smithsonian Astrophysical Observatory, a Presidential medallist and his name is synonymous with comets. He was one of the few great innovative thinkers in twentieth century planetary science. Yet through it all, he remained just Fred to all who knew him. Whether you were a young student or a distinguished internationally recognized scientist, this gentleman treated everyone with the same kindness and respect. The entire planetary science community has benefited immeasurably from his wide-ranging insights; we've lost a creative scientist and a kind mentor - but he remains a superb role model for us all.
This obituary is based on one by D.K. Yeomans and J. Veverka that appeared in "Nature" (4 Nov. 2004, vol. 432, p. 31).
Photograph provided by J. Veverka.