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 panels responsible for the report were chosen for their special competences and with regard for appropriate balance.

This project was supported by the National Aeronautics and Space Administration under Grant No. NAG5–6916, the National Science Foundation under Grant No. AST–9800149, and the Keck Foundation.

Cover: The montage on the front cover consists of one image from each of the seven panel reports in this volume. Top left: x-ray image showing loops of million-degree plasma in the solar corona (page 240). Top middle: optical/ infrared image of the stars at the very center of our galaxy in orbit around the putative black hole located there (page 115). Top right: radio map of the giant elliptical galaxy Messier 87 showing the structure of the huge cloud of relativistic plasma encompassing the galaxy and powered by the central black hole (page 187). Middle: x-ray image of the nearby supernova remnant E0102–72.3 showing the expanding shell of hot gas formed by the supernova explosion (page 37). Middle right: simulated interferometric image reconstruction of how an Earth-like planet around a nearby star would appear to the Terrestrial Planet Finder (page 348). Bottom right: artist’s conception of the Laser Inteferometer Space Antenna orbiting Earth and superimposed on the ripples in space-time produced by the gravitational power of merging supermassive black holes (page 144). Bottom left: computer visualization of the hot gas in a theoretical chunk of the universe from a cosmological simulation (page 292).

Library of Congress Control Number: 2001093504

International Standard Book Number: 0-309-07037-6

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Copyright 2001 by the National Academy of Sciences. All rights reserved.

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