Astrophysicist and space pioneer dies
Aug 10, 2006
The US astrophysicist James Van Allen died yesterday aged 91. Van Allen was best known for his studies of the Earth's magnetosphere -- the region of space filled by the Earth's magnetic field. In particular, he found bands of intense radiation, later named the Van Allen radiation belts, which he discovered using the first US satellite, Explorer 1. He also conducted the first surveys of the radiation belts of Jupiter and Saturn using the Pioneer 10 and 11 spacecraft.
Born on 7 September 1914, Van Allen graduated from the Iowa Wesleyan College in 1935 and then received a Masters and PhD from the University of Iowa. In April 1942, after a spell at the Carnegie Institution of Washington, he moved to the Applied Physics Laboratory at the Johns Hopkins University in Maryland, where he helped develop anti-aircraft technology for use on board ships. Later that year he was commissioned as an officer in the US Navy, field testing his anti-aircraft technology in the Pacific Ocean.
After the war Van Allen started work on high-altitude research, first at the Applied Physics Laboratory and, after 1950, at the University of Iowa. He and his graduate students used the university's football field to launch rockets designed to carry out cosmic-ray experiments above the atmosphere, and in 1953 discovered electrons believed to be responsible for the northern and southern lights. Then in 1955 Van Allen and a number of other scientists developed plans to launch a scientific satellite during the International Geophysical Year in 1957--58. Following the success of the Soviet Union's Sputnik 1 satellite, the Explorer spacecraft went into orbit on 31 January 1958.
Among Van Allen's instruments was a Geiger counter that showed regions of intense radiation surrounding the Earth. These regions consist of high-energy charged particles that are trapped in the Earth's magnetic field and follow roughly helical paths. The lower belt, which exists between about 1000km and 5000km above the equator, contains electrons and protons, while the upper belt, from 15000km-25000km above the equator, consists largely of electrons. This discovery marked the birth of magnetospheric physics, a field that would subsequently be studied by hundreds of scientists across the world.
Following the success of Explorer 1, Van Allen was involved in a number of major space projects. These included the first four Explorer spacecraft, the first Pioneer probes and several Mariner spacecraft. He remained at the University of Iowa until his retirement in 1985, having headed the university's physics department since 1951. He continued with research following his retirement, continuing to monitor data from Pioneer 10 and working on the Galileo probe to Jupiter. He was a teacher and mentor to large number of doctoral, graduate and undergraduate students, and received many awards. These included the US National Medal of Science and the Royal Swedish Academy of Sciences' Crafoord Prize.
About the author
Edwin Cartlidge is News Editor of Physics World