Opportunities in Cosmic-Ray Physics and Astrophysics

NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.

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The National Research Council was established by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academys purposes of furthering knowledge and of advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce Alberts and Dr. Harold Liebowitz are chairman and vice chairman, respectively, of the National Research Council.

This project was supported by the National Aeronautics and Space Administration under Grant No. NAGW-3557.

Front Cover: Radio map of the supernova remnant Cassiopeia A made with the National Radio Astronomy Observatorys (NRAO) Very Large Array. The bright ring of radio emission marks the interface between the rapidly expanding sphere of ejecta from the supernova and the shock-heated interstellar medium outside. This supernova occurred about 300 years ago, and the sphere is now about 10 light-years across. Acceleration of cosmic rays is thought to occur at shocks driven by expanding supernova remnants. (Courtesy of NRAO.)

Back Cover: Interactions of cosmic-ray protons and nuclei with the gas in the interstellar medium create all kinds of secondary particles. Among these are neutral -mesons, which in turn produce high-energy rays from the decay 0 . The back cover shows a map in galactic coordinates of the diffuse -ray flux seen by the EGRET instrument on the Compton Gamma-Ray Observatory. Interpretation of these observations confirms that the cosmic-ray sources must supply about 3 1040 ergs/s. (Courtesy of NASA.)

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Copyright 1995 by the National Academy of Sciences. All rights reserved.

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