The Invisible Universe978-1-4615-8184...Earth visible and invisible images of those totally alien worlds. We are in a period of grand technological progress, a time of learn ing, of

The Invisible Universe

George B. Field, formerly Director of the

Harvard-Smithsonian Center for Astrophysics,

is now the Robert Wheeler Willson Professor

of Applied Astronomy at Harvard University

and Senior Physicist at the Smithsonian

Astrophysical Observatory.

Eric) Chaisson, formerly a member

of the Harvard faculty, is now

Professor of Astronomy at Haverford College.

Thomas P. Stephenson, formerly Director of the

Harvard-Smithsonian Center for Astrophysics

Image Processing Facility, is currently Manager of

The Analytic Sciences Corporation (TASC)

Image Processing Laboratory.

The Invisible Universe

Probing the frontiers of astrophysics

by

GEORGE B. FIELD and ERIC J. CHAISSON

Astronomical Images and Descriptions

by

Thomas P. Stephenson

Birkhiiuser Boston . Basel . Stuttgart

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior permission of the copyright holders.

Copyright © 1985 by George B. Field

Softcover reprint of the hardcover 1st edition 1985

and Eric J. Chaisson

Library of Congress Cataloging in Publication Data

Field, George B., 1929-The invisible universe.

Includes index. 1. Astronomy. 2. Radioastronomy. 3. Astrophysics.

I. Chaisson, Eric. II. Tide. QB43.2.FH 1984 520 84-24621 ISBN 978-0-8176-3235-9 ISBN 978-1-4615-8184-0 (eBook) DOI 10.1007/978-1-4615-8184-0

ISBN 978-0-8176-3235-9

To Susan and Lola

Table of Contents

Preface ........................................... ix

Acknowledgments ................................. xiii

1 Radiation Visible and Invisible: Keys to the Universe .................................. 1

2 Interstellar Space: Dark Realms 0/ the Nighttime Sky . ...................... 27

3 Sun and Stars: Sites o/Invisible Activity ............................ .43

4 Planets, Life, and Intelligence: Are ~ Alone? .................................... 59

5 Galaxies: Nature's Grand Structures ............................ 77

6 Cosmic Violence: Black Holes, Quasars, and Beyond . ..................... 99

7 Universe: Its Large-Scale Structure . ............................ 119

8 Forces of Nature: The Limits o/Knowledge ............................ 139

Epilogue ......................................... 153

Appendices ....................................... 157

Glossary ......................................... 177

Suggestions for Further Reading ....................... 189

Index ................................ " ........... 191

VII

Preface

.. . And indeed, these latest centuries merit praise because it is during them that the arts and sciences, discovered Iry the ancients, have been reduced to so great and constantlY increasing perfection through the investigations and experiments of clear-seeing minds. This development is particularlY evident in the case of the mathematical sciences. Here, without mentioning various men who have achieved success, we must without hesitation and with the unanimous approval of scholars assign the first place to Galileo Galilei, Member of the Acadmry of the Lincei. This he deserves not onlY because he has effectivelY demonstrated faUacies in many of our current conclusions, as is amplY shown Iry his published works, but also Iry means of the telescope (invented in this country but greatlY perfected Iry him) he has discovered the four sateOites of Jupiter, has shown us the true character of the Milky wa~ and has made us acquainted with spots on the Sun, with the rough and cloudy portions of the lunar surface, with the threefold nature of Saturn, with the phases of Venus and with the physical character of comets. These matters were entirelY unknown to the ancient astronomers and philosophers; so that we may trulY say that he has restored to the world the science of astronomy and has presented it in a new light.

From the publisher's preface to Galileo's Dialogues Concerning Two New Sciences, Leiden, 1638

EARLY IN THE SEVENTEENTH CENTURY, Galileo Galilei trained his newly invented telescope on the heavens, almost instantaneously creating a revolution in astronomy, as well as a breakthrough in human perception. Viewing for the first time blemishes on the Sun, rugged mountains on the Moon, and whole new worlds orbiting Jupiter, he demolished the Aristotelian philo-

ix

THE INVISIBLE UNIVERSE

sophy of cosmic immutability. Indeed, the Universe changes; and so does our perception of it.

Nearly four centuries later, we are experiencing another period of unsurpassed scientific achievement - a revolution in which contemporary astronomers are revealing the invisible Universe as Galileo once revealed the visible Universe. In the last two decades, we have learned how to detect, measure, and analyze invisible radiation streaming to us from dark objects in space. And once again our perceptions are changing.

Consider these recent advances made with instruments that are sensitive to radiation invisible to the human eye:

• Perhaps as much as ninety percent of the matter in the Universe is dark, invisible even to large optical telescopes.

• The fiery creation of the Universe itself is revealed only by an invisible radio emission, called the cosmic background radiation.

• Sharply tuned radio emissions from atoms and molecules in space demonstrate a rich chemistry at work in the dark depths of space between the stars of our nighttime sky.

• Strong radio signals, emitted by the powerful cores of the quasi-stellar sources (or quasars), seem to imply that matter is being ejected at speeds greater than that oflight.

• Infrared waves, emanating from warm, compressed clouds in interstellar space, indicate that new stars are forming at this moment at myriad sites within them.

• Ultraviolet radiation, sampled by telescopes orbiting above our hazy atmosphere, is helping us to understand the birth, maturity, and death of stars.

• X rays (as well as radio and infrared waves), emanating from the heart of our Milky Way Galaxy, can be explained by a colossal whirlpool of hot gases in orbit around a supermassive black hole.

• Gamma rays, radiating from compact regions near the center of our Galaxy, must originate by the annihilation of antimatter - the strange opposite of matter on Earth.

From Earth and planets to stars and galaxies, astronomers and astrophysicists have accelerated their exploration of previously uncharted space. Over the course of the past two decades we have begun to unravel the mystery of the greatest puzzle of all: the Universe itsel£

We still ask the same questions as did the ancients about ourselves, our environment, and our place in the cosmic scheme of matter and life. We seek a deeper understanding of the starry points of light in the evening sky.

"

Preface

We strive to understand the origin and destiny of things. But our present attempts to find answers are aided by experimental tools made possible by modem technology: telescopes to gather information about the astronomical Universe; high-energy accelerators to penetrate the sub-microscopic world of elementary particles; automated space probes to gather data unavailable on Earth; and sophisticated computers to help keep pace with the increasing wealth of new information.

Computerized telescopes now operate, from the ground and from orbit, in each of the invisible domains of the electromagnetic spectrum. Radio telescopes as large as engineers can build them scan the Universe for signals that cannot be observed visually. State-of-the-art infrared detectors fly aboard high-altitude balloons, reconnaissance aircraft, and satellites, seeking the warm clouds that mark the birthplaces of stars in space. Telescopes aboard spacecraft map distant sources of potent ultraviolet, x-ray, and gamma-ray emission from previously unknown exotic astronomical objects. These are not merely passive probes like the pioneering satellites that marked the dawn of the Space Age a mere quarter-century ago, but complete orbiting observatories operated remotely by teams of scientists and engineers, much like major ground-based telescopes. Robot space probes also navigate through the system of known planets, telemetering to Earth visible and invisible images of those totally alien worlds.

We are in a period of grand technological progress, a time of learning, of groping in the darkness - more a time of exploration than of mature science. Sampling the Universe's rich spectrum of radiation to uncover its myriad forms of matter, we currendy strive to fit our lode of recent discoveries into a newly emerging scientific philosophy. Galileo would have been pleased.

In this book, we aim to share with the interested layperson a timely survey of our new cosmos, much of which is inherendy invisible. Discussing stars, galaxies, and especially the hidden matter among them, our work summarizes key discoveries made in this golden age of astronomy which we now share. In each chapter, we concentrate on what we have recendy leamed, including the main problems currendy puzzling us; we then discuss how we might attack those problems with observational equipment and theoretical insight expected to emerge during the remaining years of this century.

Our book is inspired by the recendy completed Report of the Astronomy Survey Committee, which recommends a program of astronomical research for the 1980s. The Report resulted from a two-year national study of the goals, aspirations, and objectives of the American astronomical community. Chaired by one of us (G.B.E), the study was commissioned by the National Academy of Sciences at the request of the Federal Government

XI


We hope that this book, as well as the Report* from which it derives, will aid in developing long-term policies designed to unlock secrets of the Universe for the good of all humankind.

We are indebted to Drs. Robert Harlow, Alan Lightrnan, and Mark Stier for a careful reading of the manuscript, and to our illustrator, Torn Stephenson, for contributing to the section entitled 'i\stronornical Image Precessing" that begins on page 13.

XII

George B. Field, Cambridge, Massachusetts, and Eric j. Chaisson, Haverford, Pennsylvania

Winter, 1984

,. Astronomy and Astrophysics for the 1980s. Volume 1: Report of the Astronomy Survey Committee Volume 2: Reports of the Panels Volume 3: Challenges to Astronomy and Astrophysics: Working Documents of the Astronomy Survey Commitee (National Academy Press, 1982, Washington, D.C.)

Acknowledgments

Images for the color plates are provided by the following individuals and institutions:

Observers J. Burns D. Chance p. Crane J. Dickel G. Dulk G. Fazio E. Feigelson W. Forman D.Gary W. Gilmore C. Jones M. Morris

Institutions Columbia University

G. Neugebauer 1. de Pater M. Reid R. Schild E. Schreier E. Seaquist C. Snyder J. Stocke R. Tresch-Fienberg G. Withbroe F. Yusef-Zadeh

Harvard-Smithsonian Center for Astrophysics Jet Propulsion Laboratory, California Institute of Technology National Radio Astronomy Observatory Space Telescope Science Institute University of California, Los Angeles

Polaroid Corporation provided additional support in the reproduction of the color plates.

Quotations preceding each chapter were taken, with permission, from the following sources:

PREFACE: Dialogues Concerning Two New Sciences by Galileo Galilei, Leiden, 1638; translated by H. Crew and A. de Salvio, 1914, The Macmillan Co., New York.

XliI


CHAPTERS 1, 2, 4, 5: The Sidereal Messenger: Unfolding Great and Marvelous Sights, and Proposing Them to the Attention o/Every One, But Especially Philosophers and Astronomers by Galileo Galilei, Venice, 1610; translated by E.F. Carlos, Dawsons of Pall Mall, London.

CHAPTERS 3, 6: History and Demonstrations Concerning Sunspots and Their Phenomena by Galileo Galilei, Rome, 1613; translated by S. Drake, 1957, Anchor, New York.

CHAPTER 7: Dialogue on the Two Chief World Systems by Galileo Galilei, Florence, 1632; translated by S. Drake, 1967, 2nd ed., Univ. Ca. Press, Berkeley and Los Angeles.

CHAPTER 8: The Assayer by Galileo Galilei, Rome, 1623; translated by S. Drake, 1957, Anchor, New York.

EPILOGUE: Dioptrics by Johannes Kepler, Augsburg, 1611; translated by E.F. Carlos, Dawsons of Pall Mall, London.

XIV