Table Of ContentlilHI IE
IINVIISIIBLIE
SIKY
ROSAT ANO THE AGE OF
X-RAY ASTRONOMY
BERND ASCHENBACH • HERMANN-MICHAEL HAHN • IOACHIM TRUMPER
TRANSLATED BY HELMUT IENKNER
c
SPRINGER SCIENCE+BUSINESS MEDIA, LLC
Originally published as Der unsichtbare Himmel, © 1996 by Birkauser Library of Congress Cataloging-in-Publication Data
Verlag, Basel, Switzerland.
Aschenbach, B.
© 1998 Springer Science+Business Media New York The invisible sky : ROSAT and the age of x-ray astronomy / Bernd
Originally published by Springer-Verlag New York, Ine. in 1998 Aschenbach, Hermann-Michael Hahn, Joachim TrUmper; [translated by
Helmut Jenkner].
p. cm.
AII rights reserved. No part ofthis publication may be reproduced, stored
ISBN 978-1-4612-7222-9 ISBN 978-1-4612-1628-5 (eBook)
in a retrieval system, or transmitted, in any form or by any means,
DOI 10.1007/978-1-4612-1628-5
electronic, mechanical, photocopying, recording, or otherwise, without
1. X-ray astronomy. 2. ROSAT (Artificial satellite) 1. Hahn.
the prior written permission of the publisher.
Hermann-Michael. II. TrUmper, J. (Joachiml, 1933- III. Title.
QB472.A83 1993
522'.6883-dc21 97-34139
CIP
Printed on acid-free paper.
987654321
ISBN 978-1-4612-7222-9 SPIN 10557928
Table of Contents
-
Preface 7 Imaging of X-Rays 51 5
An Artificial "Optic Nerve" 52
Introduction 9 Building a Satellite 53
Commands from Bavaria 56
The Invisible Sky 9
Early Morning Shock 59
The Most Accurate X-Ray Map 63
The History of X-Ray Astronomy 17
Astro-Navigation for ROSAT 63
X-Rays from the Sun? 20
A Fortuitous Discovery 21 X-Ray Astronomy in Our Galaxy 67
Filling up the Sky 22
X-Rays from a Comet 67
The Moon as Observing Assistant 23
X-Rays from the Moon 71
Rotating Blinders 26
The Demystification of the Sky 71
With Uhuru Toward New Frontiers 26
The Sun as a Prototypical Star 72
Cygnus Cycles 28
What Heats the Corona? 72
Magnetic Remote Sensing 30
The Hertzsprung-Russell Diagram 74
Einstein and EXOSAT 32
Helpful Mass Screenings 76
ROSAT - Creating a Satellite 37 Magnetic Fields Determine X-Ray
Luminosity 78
A New Type of Detector 37 ROSAT Registers Strongest X-Ray Burst 80
A Key Experience 38 X-Ray Views into Cosmic Delivery Rooms 81
Pulsars - Energy Beacons in the Universe 38 X-Rays from the Sirius System 85
The HEXE Balloon Program 40 The End of a Solar-Type Star 86
The Search for the Black Hole 41 Consequences of Proximity 87
Contacts with Moscow 42 The Source of the X-Rays 87
ROSAT - The ROentgen SATellite Project 43 Magnetic White Dwarfs 90
Grazing ReVections 45 A Mysterious Gap 92
Technical Preparations 46 Exploding Stars 92
Difficult Production 47 Supernova 1987 A 93
How to Glue Glass to Metal? 49 ROSAT's First Measurements 96
ROSAT Goes International 50 The Fast Supernova 1993 J 98
-
6 Galactic Supernovae 99 A New X-Ray Pulsar 138
A Stellar Explosion in the Stone Age 100 Super-Bubbles in the LMC 138
Supersonic Stellar Debris 113 The 30 Doradus Complex 141
Pulsars in X-Rays 114 The Andromeda Galaxy 142
Revealing Cooling 115 Starburst Galaxies 146
Enigma Geminga 116 Active Galaxies 149
Classical X-Ray Binaries 117 An End to the Confusing Variety? 152
Difficult Search 118 Multispectral Cooperation 154
Black Holes 118 Gigantic Energy Beacons 155
The Particle Slingshot SS 433 119 Clusters of Galaxies 155
Impenetrable Clouds 123 A Deep View Through the Lockman Hole 158
A Hot Neighborhood 127
Bubbles in the Milky Way 127 Epilogue 165
The Galactic Center 129
List of Acronyms 169
Perhaps a Black Hole? 134
Index 171
X-Ray Astronomy Outside Our
Galaxy 135
Our Nearest Neighbors 135
Fusion Processes on the Surface 137
Preface
-
Astronomy is not confined to the exploration of the "courage of omission" and concentrate on those
7
visible sky: Since the fifties, scientists have opened areas that can be conveyed without substantial
more and more new windows to the universe, prerequisites; but we have tried to take into
making it possible to study numerous new aspects account all crucial aspects and have striven for
of cosmic events. factual correctness. We also used this courage
The German science satellite ROSAT, circling of omission when personal contributions of the
Earth since June I, 1990, is an important milestone investigators working with ROSAT were involved.
on this road. Its data have provided us not While we mention scientists by name in the
only with a complete survey of the x-ray sky in historical chapters, we preferred to attribute all
several colors, but also with important insights ROSAT results to the satellite itself, as it were
into normal and exotic cosmic objects. It can be otherwise, the list of names would have grown too
said without exaggeration that the entirety of these long, and the danger of forgetting one or the other
data has changed our view of the world in which would have been too high.
we live. We have tried to find words to describe the
Soon after launch, we wanted to make the fantastic world of ROSAT, and to join them with
results of our astronomy with ROSAT available the most intriguing images of the invisible sky, for
to the public. But requests from the publisher those who make science projects like the ROSAT
had to be put off for quite some time. For x -ray satellite possible with their tax contributions.
scientists at the Max Planck Institute, research Our thanks go to them as well as to the individuals
and the publication of the results in scientific providing help and review during the development
journals must take precedence. That the thoughts of this book.
and ideas finally resulted in an actual book
is due to the efforts of the science journalist Bernd Aschenbach
among us, who sifted through the rich harvest Hermann-Michael Hahn
of ROSAT data for several months and prepared Joachim Triimper
this book in continuous dialogue with the rest July 1996
of us. Of course, we had to develop some Garching, Germany
Introduction
-
The Invisible Sky achieved the second "border crossing" in Bonn, 9
Germany, in 1888 when he generated and detected
For thousands of years our visual perception radio waves. The Scottish physicist James Clerk
has ruled our notions about the world. What Maxwell had predicted their existence as part of
we see with our own eyes leaves much deeper his theory of electromagnetic radiation more than
impressions in our experience than any other a quarter century earlier. Finally, in 1895, Wil
kind of information -perhaps with the exception helm Konrad Rontgen detected a strange new kind
of pain, but this is mainly a protective function. of radiation that could penetrate matter. These
"A picture is worth a thousand words" is the core mysterious rays, which he termed "x"-rays could
principle of modern information and advertising even disclose details, especially bones, inside the
strategies. human body.
But what we see is only a minute portion of re Soon it became obvious that Rontgen's x
ality. Not because our sense of vision is insufficient rays - unlike Herschel's infrared and Hertz's radio
to probe extremely distant or exceedingly small waves - were located far beyond the violet end
objects: We have learned to overcome such short of the spectrum. Visible light, as another conse
comings. We can explore distant galaxies with quence of Maxwell's theory, was only a small part
powerful telescopes or send space probes to the of the electromagnetic spectrum, comparable to
planets of our solar system, providing us with data just a single octave of a much wider keyboard.
and images of our neighboring worlds, or we can These discoveries had considerably broadened
peer into the microcosm using microscopes. the horizon for physicists within barely a century,
But our eyes can show us only a very limited but for some time they had little direct influence
slice of the world, because visible light carries on astronomy. Earth's atmosphere does not per
only a small part of the information about physical mit radiation other than visible light and radio
reality. Other facets remain hidden. waves to reach the ground without being fully or
The German-born astronomer William Freder partly absorbed - fortunately for all living beings
ick Herschel showed this fundamental limitation (including astronomers), since the unweakened
of our vision for the first time in 1800. He de ultraviolet, which immediately borders the violet
tected invisible forms of radiation in a simple but end of the visible spectrum, poses a serious threat
convincing experiment. Using a glass prism, he to life on Earth.
scattered the light of the sun into the colors of Although stargazers had always used the "op
the rainbow and placed thermometers at the vari tical window," it took astronomers until the middle
ous colors in order to measure the intensity of the of the twentieth century to recognize and exploit
corresponding radiation. A thermometer placed the much wider "radio window" in the atmosphere.
outside the band of colors, beyond the red end, Although the American astronomer Karl Guthe
also showed an increase in temperature. Herschel Jansky discovered the "static" originating from the
had detected infrared radiation. Heinrich Hertz Milky Way in the early nineteen thirties, detector
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