Fred L. Whipple

…of the cometary nucleus by Fred Whipple would do the same for cometary physics. Whipple combined many of the ideas of the day and suggested that the cometary nucleus was a solid body made up of volatile ices and meteoritic material. That was called the “icy conglomerate” model but also…

Thus, Whipple explained the slow shrinking of Encke’s orbit as the result of tangential forces that were pointed opposite to the comet’s direction of motion, causing the comet nucleus to slow down, slowly shrinking the orbit. That model also explained periodic comets whose orbits were growing,…

…as those by Oort and Whipple in 1950, but astronomers occasionally followed up his ideas. In 1968 Egyptian astronomer Salah Hamid worked with Whipple and Marsden to study the orbits of seven comets that passed near the region of Kuiper’s hypothetical comet belt beyond Neptune. They found no evidence of…

Whipple’s classic paper in 1950 had suggested that as comets lost material from the surface, some particles were too heavy to escape the weak gravity of the nucleus and fell back onto the surface, forming a lag deposit. That idea was later studied by American…

American astronomer Fred Whipple explained it in 1950 as the effect of jet forces produced by sublimation of water ice on the surface of the comet’s nucleus, in combination with the rotation of the nucleus.