X Rays From the Rest of the Universe

NOV 01, 1995

X‐ray sources in space are serving more and more as valuable laboratories for astrophysics, nuclear physics, relativity, plasma physics and cosmology.

DOI: 10.1063/1.881441

David J. Helfand

Just as x rays from a cathode‐ray tube in Wilhelm Röntgen’s laboratory revealed the bones in his wife’s hand, x rays from space have revealed new objects and physical processes hidden from the view of optical telescopes. X rays from beyond Earth’s atmosphere were first detected in 1949 in a 5‐minute V‐2 rocket observation of the Sun. Thirteen years later, the first nocturnal rocket flight quite unexpectedly discovered the existence of a diffuse isotropic glow of 10‐kilo‐electron‐volt x rays across the celestial sphere, as well as the first discrete source of x‐ray emission from beyond the Solar System. By 1965 the number of known sources of celestial x rays totaled 10; at this writing the number exceeds $10^{5} .$

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More about the Authors

David J. Helfand. Columbia University, New York City.