Observational Astrophysics

518 Pages·1998·11.876 MB·English

by  Pierre Léna, François Lebrun, François Mignard (auth.)

I.
-&- ~ ASTRONOMY A:\fO
I
I ,L \ --\ ASTROPHYSICS LJBRARY
~
LIBRARY
Series Editors: I. Appenzeller, Heidelberg, Germany
G. Borner, Garching, Germany
M. Harwit, Washington, DC, USA
R. Kippenhahn, Gottingen, Germany
P. A. Strittmatter, Tucson, AZ, USA
V. Trimble, College Park, MD, and Irvine, CA, USA
Springer-Verlag Berlin Heidelberg GmbH
t\STRONOMY AND
~~;-l
ASTROPHYSICS LIBRARY
LIBRARY
Series Editors: 1. Appenzeller . G. Borner . M. Harwit . R. Kippenhahn
P. A. Strittmatter . V. Trimble
Theory of Orbits (2 volumes)
Volume 1: Integrable Systems and Non-perturbative Methods
Volume 2: Perturbative and Geometrical Methods
By D. Boccaletti and G. Pucacco
Galaxies and Cosmology
By F. Combes, P. Boisse, A. Mazure and A. Blanchard
The Solar System 2nd Edition By T. Encrenaz and J.-P. Bibring
The Physics and Dynamics of Planetary Nebulae By G. A. Gurzadyan
Astrophysical Concepts 2nd Edition By M. Harwit
Stellar Structure and Evolution By R. Kippenhahn and A. Weigert
Moderu Astrometry By J. Kovalevsky
Supernovae Editor: A. Petschek
General Relativity, Astrophysics, and Cosmology
By A. K. Raychaudhuri, S. Banerji and A. Banerjee
Tools of Radio Astronomy 2nd Edition
By K. Rohlfs and T. L. Wilson
Atoms in Strong Magnetic Fields
Quantum Mechanical Treatment and Applications
in Astrophysics and Quantum Chaos
By H. Ruder, G. Wunner, H. Herold and F. Geyer
The Stars By E. L. Schatzman and F. Praderie
Gravitational Lenses By P. Schneider, J. Ehlers and E. E. Falco
Relativity in Astrometry, Celestial Mechanics and Geodesy
By M. H. Soffel
The Sun An Introduction By M. Stix
Galactic and Extragalactic Radio Astronomy 2nd Edition
Editors: G. L. Verschuur and K. I. Kellermann
Reflecting Telescope Optics (2 volumes)
Volume I: Basic Design Theory and its Historical Development
Volume II: Manufacture, Testing, Alignment, Modem Techniques
By R. N. Wilson
Galaxy Formation By M. S. Longair
Astrophysical Formulae 3rd Edition (2 volumes)
Volume I: Radiation, Gas Processes and High-Energy Astrophysics
Volume II: Space, Time, Matter in Cosmology
By K. R. Lang
P. Lena F. Lebrun F. Mignard
Observational
Astrophysics
Translated by S. Lyle
Second Revised and Enlarged Edition
With 254 Figures, 67 Tables and 61 Exercises
i
Springer
Pierre Lena Fran~ois Mignard
Observatoire de Paris-Meudon Observatoire de la Cote d' Azur
Universite de Paris VII Centre de Recherche en Geodynamique et Astrometrie
5, Place Jules Janssen Av. Copernic
F-92l95 Meudon Principal Cedex, France F-06130 Grasse, France
e-mail: [email protected] e-mail: [email protected]
Fran~ois Lebrun Translator
a
Commissariat l'Energie Atomique/Sac\ay Stephen Lyle
DSMJDAPNIAlSAp
8, Impasse du Coteau
F-91191 Gif-sur-Yvette Cedex, France
F-69480 Pommiers, France
e-mail: [email protected]
e-mail: [email protected]
Cover picture: The array of six free-flying satellites (five 1.5-m telescopes plus a central interferometric
recombinating hub) is a configuration studied since 1997 by the European Space Agency for the mission
DARWIN, aimed at the detection and spectroscopy of Earth-like extrasolar planets, to be observed in the
near-infrared part of the electromagnetic spectrum (ca. 5-20 micrometers). The satellites would be
deployed ca. 5 astronomical units from the Sun. In the background appears, as simulated, the view that
such an interferometer would give of our own inner Solar system (Venus, Earth and Mars), as seen at a
distance of 10 parsec, after some hours of measurement. The bright Sun is eliminated by the optical system,
in order to view the fainter planets. (Courtesy of Bertrand Mennesson & Marc Ollivier)
Title ofthe original French edition: Astrophysique: Methodes physiques de ['observation
© InterEditions, Paris et CNRS Editions, Paris 1986, 1996
CIP data applied for
Die Deutsche Bibliothek - CIP-Einheitsaufnahme
Lena, Pierre: Observational astrophysics: with 67 tables and 61 exercises / P. Lena; F. Lebrun; F. Mignard. Trans!. by
S. Lyle. - 2., rev. and en!. ed. - Berlin; Heidelberg; New York; Barcelona; Budapest; Hong Kong; London; Milan;
Paris; Singapore; Tokyo: Springer, 1998 (Astronomy and astrophysics library) Einheitssacht.: Methodes physiques
de I'observation <eng!.>
ISSN 0941-7834
This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, speci
fically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or
in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the
provisions ofthe German Copyright Law of September 9, 1965, in its current version, and permission for use must always
be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law.
ISBN 978-3-642-08336-5 ISBN 978-3-662-03685-3 (eBook)
DOl 10.1007/978-3-662-03685-3
© Springer-Verlag Berlin Heidelberg 1988, 1998
Originally published by Springer-Verlag Berlin Heidelberg New York in 1998.
Softcover reprint of the hardcover 2nd edition 1998
The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the
absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and
therefore free for general use.
Typesetting: Data conversion by EDV-Beratung F. Herweg, Hirschberg
Cover design: design & production GmbH, Heidelberg
SPIN: 10552651 55/3144 - 5 43210 - Printed on acid-free paper
Preface to the Second English Edition
The success of the first English edition led Springer-Verlag to publish this
second one, and we thank Prof. Beiglbock as well as Mrs. A. Kubler for their
action during this venture. The authors are deeply indebted to Mr. Stephen
Lyle for his careful and patient translation of the French version and for his
friendly cooperation with us.
Progress is becoming incredibly rapid in astronomical observing tools;
since the completion of this book, the Infrared Space Observatory (ISO) has
been launched and has completed its mission, the VIRGO and LIGO gravita
tional detectors are under construction, the Next Generation Space Telescope
is under design, and the European Very Large Telescope has seen its first
light, as will soon the SOFIA airborne submillimeter observatory, the VLT
and Keck optical interferometers, and many other powerful instruments.
We nevertheless hope that the basic physical principles outlined in this
book will remain useful for the students, astronomers, physicists and en
gineers who are busily planning the conception or use of new or existing
instruments.
The Internet has revolutionized access to information and may deeply
modify the role of textbooks in the future. Although rapidly evolving, Internet
sites containing astronomical information can be readily listed and offer a
start to fruitful navigation for the motivated reader. We have provided such
a list, at least as a starting point, in Appendix E. This list was kindly compiled
by Jean-Marc Deltorn, a graduate student at the Laboratoire d'Astronomie
Spatiale (Marseille), and we greatly thank him for this work.
June 1998 The authors
Preface to the Second French Edition
In memory of Philippe Delache
Up until the middle of the Twentieth century, the tools of astronomical ob
servation consisted almost exclusively of telescopes, spectrometers and pho
tographic plates, and these tools had been more or less brought to perfection
through the combined efforts of astronomers and opticians. The sudden ar
rival of radioastronomy, followed by infrared, ultraviolet, X-ray and y-ray
astronomy, the possibility of observation from space, in situ exploration of
the solar system, and the advent of computer technologies, with their prodi
gious capacity for processing data, represented so many events that were to
transform astrophysical observation. The transformation has not yet reached
its conclusion, and this is indeed the main difficulty facing any attempt to
provide an overview.
The aim in the present text is therefore methodological. Rather than at
tempting to detail the diverse techniques related to each wavelength region,
which are so well treated in more specialised works, our aim was to present the
physical ideas behind the instrumentation used: telescopes forming images,
spectrometers analysing them, and detectors converting them into signals.
In this approach, the main principles are identified, and the ultimate limita
tions allowed by physical theory are revealed. Consequently, the underlying
theme will be the properties of the photon (or those of the electromagnetic
wave), this being the main information carrier in astrophysics. The gathering,
measurement, and quantitative analysis of this information are the subject
matter of the present book, determining what to include and what to sacri
fice. The same applies to the few mathematical tools exposed in appendixes
with a view to homogenising notation. The methodological approach also
limits what is covered, and no claim is made to comprehensive discussion of
all observational methods, nor to exhaustive and systematic coverage of the
tools they involve.
Never before has such a rich panoply of instruments been available to those
whose curiosity has turned them toward the heavens as now, at the close of
this millennium: at ground level, telescopes for the visible, the infrared, and
radiofrequencies, and the detection of cosmic rays; in space, observatories
covering all wavelengths of the spectrum. On the Earth, as in space, optical
VIII Preface to the Second French Edition
interferometers are appearing. Neutrino astronomy, and the study of gravita
tional waves, which were only envisaged in the first edition of this book, have
today become a reality. At the same time, the complexity, the time required
for developments, and the growing cost of equipment have radically changed
the way of working and, indeed, the profession of astronomy. Nowadays, it
is often the case, and maybe too often, that those who design and make the
instruments are not the same as those who use them and who interpret the
observations made with them. The aim of this book will have been accom
plished if it helps some astronomers to progress in the quest for data, whilst
at the same time, it gives others an insight into the working of those black
boxes which have become today's tools.
France's contribution to this progress has been considerable: Fourier
transform spectroscopy, radio and optical aperture synthesis, astrometric
techniques, lightened mirrors, adaptive optics, gamma imaging, gravitational
wave detectors; the list continues, and is likely to go on doing so, provided
only that the same enthusiasm guides so many brilliant young people into
the ways of observation and its tools.
The first edition of this work came out in 1986, and its English translation
(Springer-Verlag) in 1988. It was the result of a course given since 1978 to
students for the Master's degree in Astrophysics and Space Techniques, at
the University of Paris VII, which was itself a preparation, for most of those
students, for a Doctoral degree in the same discipline.
Only ten years later, this discipline had evolved so dramatically that a
second edition had become necessary, and that was also an opportunity to
substantially rework the original text. A more coherent plan was forged: hav
ing established the necessary bases, concerning astrophysical information,
the properties of the Earth's atmosphere, and those of radiation, it proceeds
from telescopes towards spectroscopy and the detection of signals. A discus
sion of space-time frames, an area sadly lacking in the first edition, has been
supplied by Franc;ois Mignard. The part of the text devoted to high ener
gies (X-ray and 'Y-ray) has been considerably developed by Franc;ois Lebrun.
Mathematical necessities (Fourier transforms, and an introduction to proba
bility and statistics) have been transferred to appendixes in order to improve
the presentation.
We have nevertheless avoided a complete rewriting. Modifications have
simply been added, usually with dates to increase clarity, in those places
were recent developments had rendered the original text somewhat obsolete.
Signal processing, which has made a great leap forward with the advent
of computerised data processing techniques, indeed deserves a whole book
to itself, although it occupies only a modest fraction of the present work.
The bibliography, which has been brought up to date, gives only educational
references and overviews. Some tables and figures have been added, as well
as a certain number of solutions to exercises, thanks to the help of David
Mouillet. Several errors in the first edition, almost all corrected during the
Preface to the Second French Edition IX
English translation, have been rectified, once attention had been drawn to
them by students and colleagues, all of whom I must thank. As the volume
of the work has greatly increased, some parts appear in small print, referring
to details or more technical questions, and these can be omitted upon a first
reading.
It would be impossible to cite the names of all those colleagues, or students
who later became colleagues, who have contributed to these two editions,
or who have provided original papers. I would like to express my warmest
thanks to all of them. Special thanks are due, however, to Patrick Boisse,
Jean-Gabriel Cuby (detectors and spectroscopy), Dennis Downes (millimetre
radioastronomy), Franc;ois Lacombe (infrared), Andre Lannes, Jean-Marie
Malherbe (computer science), Didier Pelat (signal processing, Sects. 6.1.3 and
6.1.4), Jean Schneider (Sect. 7.5) and Jean Vernin (atmospheric properties),
for invaluable updating during production of this second edition. Madame
Claude Audy and Madame Helene de Castilla of InterEditions took an ac
tive part in the final presentation of the text, as did Eric Gendron through
his careful proof reading. The Centre National de la Recherche Scientifique
(France) and M. Gall also provided assistance during this revision. I was
generously hosted by the Fondation de Treilles, and express my thanks to its
members for their welcome, and the serenity which surrounds this exceptional
place.
I have dedicated this book to my friend and fellow solar astronomer,
Philippe Delache, who left us prematurely in 1994.
June 1995 Pierre Lena
Table of Contents
1. Astrophysical Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Carriers of Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Collecting and Analysing Information. . . . . . . . . . . . . . . . . . . . . 9
1.2.1 The Main Characteristics of Photons ............... 9
1.2.2 Observing Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10
1.2.3 Reaching a Systematic Description of Observation. . .. 26
1.3 Strategies and Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26
2. The Earth's Atmosphere and Space. . . . . . . . . . . . . . . . . . . . . .. 31
2.1 Physical and Chemical Structure of the Atmosphere. . . . . . .. 32
2.1.1 Vertical Structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 32
2.1.2 Constituents of the Atmosphere. . . . . . . . . . . . . . . . . . .. 33
2.2 Absorption of Radiation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 36
2.3 Atmospheric Emission .................................. 41
2.3.1 Fluorescent Emission ............................. 41
2.3.2 Thermal Emission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 44
2.3.3 Differential Measurement Techniques. . . . . . . . . . . . . . .. 47
2.4 Scattering of Radiation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 48
2.5 Atmospheric Refraction and Dispersion. . . . . . . . . . . . . . . . . . .. 52
2.6 Turbulence Structure of the Earth's Atmosphere ........... 52
2.6.1 Turbulence in the Lower and Middle Atmosphere. . . .. 53
2.6.2 Ionospheric Turbulence. . . . . . . . . . . . . . . . . . . . . . . . . . .. 60
2.7 Terrestrial Observing Sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60
2.7.1 Visible, Infrared and Millimetre Observations. . . . . . .. 60
2.7.2 Centimetre Radioastronomy and Beyond. . . . . . . . . . .. 63
2.7.3 Man-Made Pollution and Interference. . . . . . . . . . . . . .. 63
2.7.4 The Antarctic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 64
2.8 Observation from Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65
2.8.1 The Advantages of Observation from Space. . . . . . . . .. 66
2.8.2 Sources of Perturbation .. . . . . . . . . . . . . . . . . . . . . . . . .. 66
2.8.3 Choice of Orbits ................................. 72
2.9 The Moon as an Astronomical Site. . . . . . . . . . . . . . . . . . . . . .. 74
2.10 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 75
XII Table of Contents
3. Radiation and Photometry ............................... 79
3.1 Radiometry............................................ 80
3.2 Aspects of Radiation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 84
3.2.1 Blackbody Radiation. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 84
3.2.2 Coherence....................................... 85
3.3 Magnitudes............................................ 90
3.4 Photometry Through the Atmosphere. . . . . . . . . . . . . . . . . . . .. 92
3.5 Calibration and Intensity Standards ...................... 93
3.5.1 Radiofrequencies (>. > 1 mm) ...................... 94
3.5.2 Submillimetre, Infrared and Visible. . . . . . . . . . . . . . . .. 95
3.5.3 Ultraviolet and X-Rays (0.1 nm < >. < 300 nm) ...... 100
3.5.4 Gamma Radiation ................................ 102
3.5.5 Some Examples of Spectrophotometry .............. 102
3.6 Exercises .............................................. 105
4. Telescopes and Images. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 107
4.1 Image and Object in Astronomy .......................... 108
4.1.1 Geometrical Images ............................... 109
4.1.2 Gravitational Optics .............................. 114
4.2 Diffraction and Image Formation ......................... 115
4.2.1 The Zernike-van Cittert Theorem .................. 115
4.2.2 Diffraction at Infinity. Pupils ...................... 120
4.2.3 Pupils and Spatial Filtering ........................ 125
4.2.4 Waveguides and Fibre Optics ...................... 131
4.3 Telescopes ............................................. 133
4.3.1 Radiotelescopes (Beyond the Submillimetre Range) ... 133
4.3.2 Ground-Based Optical Telescopes
(Visible and Infrared) ............................. 146
4.3.3 Aperture Synthesis in the Visible and Infrared ....... 149
4.3.4 Space Telescopes, from Ultraviolet to Submillimetre .. 157
4.3.5 X-Ray Telescopes (0.1-10 keV) ..................... 159
4.3.6 y-Ray Telescopes (> 10 keV) ...................... 160
4.4 Image Degradation by the Atmosphere .................... 167
4.4.1 Perturbations of the Wavefront ..................... 168
4.4.2 Image Formation ................................. 171
4.4.3 Short-Exposure Images and Speckle Interferometry ... 172
4.4.4 Adaptive Optics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
4.4.5 Phase Perturbations in Aperture Synthesis .......... 182
4.5 Image Processing ....................................... 184
4.5.1 The Principal Solution ............................ 185
4.5.2 Methods of Information Restitution ................. 186
4.6 Exercises .............................................. 188