Van Allen found Earth's belts of radiation

WASHINGTON — James Van Allen, who helped launch the United States into space with the discovery that radiation belts surround Earth, died after a heart attack Wednesday at the University of Iowa Hospital. He was 91.

Professor Van Allen's realization that charged solar particles are trapped by Earth's magnetic field in concentric rings around the planet was the first major scientific discovery of the space age. It revolutionized scientific understanding of Earth and the solar system and created a new field of research, called magnetospheric physics.

His breakthrough came from a Geiger counter he sent into space aboard the first U.S. satellite, Explorer 1, in 1958.

The Geiger counter began clicking madly as soon as it reached orbit. The data from that and subsequent satellites showed Earth was surrounded by a vast series of nested shells of trapped particle radiation, later named the Van Allen radiation belts.

Those belts helped scientists understand everything from the northern lights to the chemical composition of space, and alerted scientists to the vast store of knowledge just outside human reach.

Professor Van Allen, who had taken only one undergraduate astronomy class, continued to measure and explore the belts around Earth, then radiation belts around Jupiter and Saturn as well. Until recently, he pursued the discovery of the edge of the heliopause, the outer boundary of the solar wind. He pored over data still coming in from the almost obsolete, Volkswagen-sized Pioneer 10.

The affable, down-to-earth scientist, whose University of Iowa office door was marked with his name and longitude and latitude coordinates, took his achievements in stride. His favorite activity, he said, was teaching the beginning astronomy class at Iowa.

Of the discovery of the radiation belts, "It was like going hunting for rabbits and encountering an elephant instead," he once said.

Time magazine put him on its cover in 1959, and again in 1961. President Reagan gave him the National Medal of Science in 1987. Professor Van Allen received the Vannevar Bush Award from the National Science Board in 1991 and the National Air and Space Museum's trophy in 2006, among many other awards.

"I believe in scientific inquiry for its own sake," he once said. "I think the history of science gives ample examples that pure investigation has enormous benefit. ... I can't tell you what this might be good for, but learning about nature is important. And lovely things turn up."