Exploring the Southern Sky: A Pictorial Atlas from the European Southern Observatory (ESO)

278 Pages·1987·61.361 MB·English

by  Svend Lausten, Claus Madsen, Richard M. West (auth.)

EXPLO RING
SvendLaustsen
Claus Madsen
THE SOUTHERN SKY
RichardM.West
A Pictorial Atlas from the
European Southern Observatory (ESO)
With 240 Photographs, Partly in Colour,
31 Diagrams and a Fold-out Plate
Springer-Verlag
Berlin Heidelberg NewY ork
London Paris Tokyo
SVEND LAUSTSEN
CLAUS MADSEN
RICHARD M. WEST
European Southern Observatory (ESO)
Karl-Schwarzschild-StraBe 2
D-8046 Garching bei Miinchen
ISBN-13: 978-3-642-64877-9 e-ISBN-13: 978-3-642-61588-7
DOl: 10.1007/978-3-642-61588-7
This work is subject to copyright. All rights arc rcscrvcd,
whether the whole or part of the material is concerned, specifi
cally the rights of translation, reprinting, re-use of illustrations,
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publication or parts thereof is only permitted under the pro
visions of the German Copyright Law of September 9, 1965,
in its version of June 24, 1985, and a copyright fee must always
be paid. Violations fall under the prosecution act of the Ger
man Copyright Law.
© Springer-Verlag Berlin Heidelberg 1987
Softcover reprint of the hardcover 1st edition 1987
Reproduction of the plates and figures:
Chemigraphia, Gebruder Czech, Munchen
Typesetting and printing:
Universitatsdruckerei H. Sturtz AG, Wiirzburg
Bookbinding:
Buchbinderci Sigloch, Kunzelsau
2124/3130-543210
Foreword
The photographs in this book combine beauty Many questions remain to be answered. How The photographs that appear in this book
and scientific relevance. The characteristics of did the galaxies form? How did our solar system have been taken with the telescopes of ESO, the
the galaxies, nebulae and other objects shown originate? No one can answer the former ques European Southern Observatory, a cooperative
have been determined by the physical laws which tion with confidence, while only preliminary venture of eight countries, Belgium, Denmark,
govern their destiny, but the resulting shapes and ideas have been developed about the latter. The France, Germany, Italy, the Netherlands, Swe
colours have a profound aesthetic appeal. detailed study of the objects shown in this book den and Switzerland. ESO's telescopes are lo
Astronomical research has begun to give us should help us to search for more definite an cated at La Silla, a 2400 meter high mountain
some idea as to how the Universe evolved. Start swers. in the Atacama desert in northern Chile, where
ing from a condition of extremely high density the skies are of an extraordinary/purity and
and temperature, an expanding Universe origi transparency. The ESO Headquarters for re
nated some twenty thousand million years ago. search and technological development is in
What preceded this stage is beyond the limits Garching near Miinchen. This book demonstrates
of our knowledge. In this expanding Universe the fruits of international cooperation in science.
multitudes of stars and galaxies formed. Study
ing them in detail allows us to push the limits L. Woltjer
of our knowledge even further back in space and Director General of ESO
time, and thereby to come closer to the mysteri
ous moment of the origin of the Universe. Along
the way we may also learn much about physics
under conditions very different from those en
countered on earth.
v
Table of Contents Acknowledgements
Introduction . . . . 1 3 Minor Bodies in the Solar System 193 First of all, we would like to thank all our col
A Guide to this Book 2 leagues who have made original images from La
3.1 Meteoroids and Minor Planets 194
Silla available for reproduction in this book.
3.2 Comets . . . . . . . . 205
1 The Universe and its Galaxies 5 They are identified in the List of Plate Data on
page 263.
1.1 A Look into F ornax 8 4 The Southern Sky and ESO 221
In addition, we gratefully acknowledge
1.2 An Ordered Sequence of Galaxies 15
4.1 A European Organization for friendly support by the following astronomers
1.3 The Local Group. . 47
Astronomy . . . . . . . . 223 in the form of texts, clarifying discussions, hints,
1.4 The Sculptor Group 69
4.2 The La Silla Observatory 223 etc.: M. Cullum, P. Grosb0l, S. Jorsiiter, A.F.M.
1.5 Multiple Galaxies. . 74
4.3 The Headquarters in Garching 247 Moorwood, S. D'Odorico, H. Pedersen, B. Rei
1.6 Clusters of Galaxies 87
4.4 The Next Generation of Telescopes 250 purth, H.-E. Schuster, P. Shaver, P. Stattmayer
1.7 Peculiar Galaxies . . 99
and M. Tarenghi. Thanks are also due to the
Glossary . . . 257 Swedish team and P. Corbern at the Roque de
2 The Milky Way Galaxy 117
Plate Data . . 263 los Muchachos Observatory, and Optronics Inc.
2.1 Panorama of the Milky Way 119 Index of Objects. 271 (Plate 34).
2.2 The Milky Way from Orion to Pup- We are particularly grateful for technical sup
pIS . . . . . . . . . . . . . . . 124 port by B. Dumoulin (photography), S. Dunlop
2.3 The Milky Way from Vela to Carina 134 (language editing), C. Jauch (drawings), H. Niel
2.4 The Milky Way from Crux to Norma 154 sen (typing), K. Kjar (proofreading), J. Quebatte
2.5 The Milky Way from· Scorpius to (photofinishing), E. Volk (typing), and H. Zodet
Scutum ............. 164 (photography).
2.6 Milky Way Objects at High Galactic Finally, we are indebted to the Director Gen
Latitude ............ 185 eral of ESO, Professor L. Woltjer, who suggested
the compilation of this book and gave continu
ous encouragement during its preparation.
S. Laustsen . C. Madsen' R.M. West
VI
Introduction
If you ever fly from Europe to South America, The outcome of all these efforts can be found of new and better photographic products on the
the chances that the person in the seat next to in professional journals and occasionally in the amateur market. Likewise, the need to observe
you is an astronomer may be larger than you media, whenever a new, exciting discovery is fainter and fainter objects has challenged the in
think. A little less than half of thc world's 6000 made. The overall picture becomes available genuity of engineers in the fields of semiconduc
professiona1 astronomers Jive in Europe and much later to the public and, due to the high tors, optics and electronics, and has also substan
many of them regularly travel to the South. The degree of specialization, also to many of the pro tially contrihuted to the development of efficient
goal of their journey lies in the dry Atacama fessional astronomers. image-processing software. Indeed, many of the
desert, more than 600 km north of Santiago de This book docs not attcmpt to evaluate in innovations that have been made at ESO in the!-ie
Chile, under the splendid southern sky. Here detail the front-line research that is done at La fields have been taken over in other disciplines
they stay at the ESO La Silla Observatory, days S:illa, nor does it claim to give an evenly balanced and by European industry.
or months at a time, scrutinizing the Universe account of modern astronomy. The present ap This book is a picture book and is meant
with the most powerful astronomical instru proach is different, not to say unusual. The idea to be used as such. Why not first have a look
ments available. has been to look over the shoulders of the astron at the two hundred Plates of southern celestial
The creation of the European Southern Ob omers and to se1ect some of the impressive im objects and fie1ds? Enjoy the beauty of these im
servatory in 1962 has had a profound impact ages of astronomical objects that have been ob ages, many of which have not been included be
upon European astronomy. With the support of tained during the past 10 years at the ESO obser fore in a popular book. The reader who wants
8 member countries, it has stimulated collabora vatory. To explain briefly why these pictures are to know more will find the details in the text
tion among astronomers in Europe and abroad, interesting, and to remind ourselves - not the and the Figures. Note also the" Guide to this
and has undertaken several major projects ad least the professional astronomers - about the Book", the Glossary, the List of Plate Data and
vancing astronomical science and technology. extraordinary beauty of the southern sky. Our the Indexes which contain much supplementary
Many discoveries, and significant progress in aim is to describe the multitude of phenomena information. It is hoped that the complete docu-
various astronomical fields, have been achieved that we witness in the Milky Way and in other . mentation will render this book useful, not only
at ESO. Astronomy may be one of the oldest galaxies, and thereby to give a kaleidoscopic to the interested layman, but also to the dedi
sdences, but in many respects it is also one of view of modern astronomical research. cated amateur astronomer and perhaps even to
the most modern. Gone are the days when the Many of the illustrations in this book are our professional colleagues.
astronomer gazed through his telescope and told based on photographs, but others have been ob
the world about his visual impressions. High tained with modern detectors. Photography and
technology has taken ovcr, so that the maximum astronomy have always been close companions
amount of information can be obtained during and they have had a profound impact on each
the precious observing time. In order to pene other. The very term "photography" was first
trate deeper into the mysteries of the Universe, introduced by the English astronomer John
the modern astronomer must work efficiently Herschel and there are numerous examples of
and with extremely sophisticated instruments. how the repeated demands by astronomers for
better and faster emulsions have stimulated pho
tochemical research and led to the availability
1
A Guide to this Book
The photographs in this book can be enjoyed spectral bands. This method is superior to using lay-out problems to maintain the principle. For
without knowledge of their provenance, but colour film in that it better reproduces the these Plates the related Figures show the orienta
readers who want to know more will find de "true" colours of astronomical objects. Some tion. Finally, in a few cases (Plates 1, 139, 178,
tailed documentation in the List of Plate Data illustrations are computer-enhanced, "false-col 199, 200, 202 and 203) it was more convenient
on page 263. A Glossary (page 257ff.) explains our" images, in order to better show particular to choose a different orientation, which is indi
many of the astronomical terms in the text. Indi details. The relevant information is given in the cated for each Plate.
vidual objects can be found easily with the help text. The List of Plate Data (p. 263) gives addi
of the Indexes (page 271 ff.). Some of the images seen in the illustrations tional information about each photo. The image
In what follows, further information is given are not celestial but result from optical reflection scale is indicated as degrees (0), arcminutes (')
about some basic features of this book and the in the telescope used. A typical effect is the or arcseconds (") per centimetre. A full circle
pictures therein. "cross", sometimes with a circular "halo" measures 360°; 1 ° = 60' = 3600"; l' = 60". The
around brighter stars. It is caused by the spider angular distance, that is the separation in the sky
that carries the secondary mirror or the plate between two objects can be calculated by mea
THE PHOTOGRAPHS holder. Very bright stars, even if they are outside suring their distance on the photo in centimetres,
the field of the photograph, may cause double and then multiplying this figure with the image
With very few exceptions, all illustrations in or multiple reflections in the telescope optics scale given in the Table.
Chapters 1-3 are reproductions of original expo with resulting" ghost" images. A typical exam The celestial positions of the photos are also
sures that were made with telescopes at the ESO ple is seen in Plate 187. In some Schmidt pictures, given in the Table of Plate Data. Astronomers
La Silla Observatory. Most of them were ob the light from bright stars at the edge of the use a coordinate system in the sky that is very
tained photographically, but some were made field is reflected from the plateholder and is seen similar to geographical longitude and latitude on
with modern detectors. Further explanation as a diffuse, fan-shaped image, perpendicular to the surface of the Earth. In this so-called equato
about CCD's is given on page 242. the edge. rial system, Right Ascension (R.A.) corresponds
Many of the pictures are reproduced in the to longitude and Declination (Dec!.) to latitude.
normal way as positive photos with white stars R.A. increases towards the east from 0 h to 24 h
on a black sky, but some are shown as negative ORIENTATION, SCALE AND POSITION (0 h-24 h), and Dec!. from the celestial South
photos, with black stars on a white sky. The Pole at -90°, over the equator at 0° to the North
"negative" presentation is quite common in as The orientation of almost all the celestial photos Pole at + 90°. The zero-point (R.A. = 0 h; Decl. =
tronomy, because the human eye is best able to in this book is such that north is up and east 0°), also known as the" Vernal Equinox", is the
discern fine differences in density against a rela is to the left. This principle has been strictly position in the sky of the Sun on March 21.
tively bright background. Faint celestial objects maintained, except in a few cases. For instance, Another system of coordinates relates to our
often come out better in a negative print. it has no meaning for Plate 50, containing the own Galaxy, and is called the Galactic coordinate
Some of the colour pictures were originally celestial South Pole, and for Plate 122, contain system. Galactic longitude and latitude describe
made on colour film. Others are regenerated col ing both celestial poles. For the wide-angle positions in the sky, relative to the plane of our
our images, which were made by superimposing Milky Way photos, Plates 124, 132, 133, 149, Galaxy, that is to the band of the Milky Way
black-and-white images obtained in different 150, 157 and 158, it would have led to serious (see also Plate 122 and the fold-out panorama).
2
They are both expressed in degrees, and the zero is the brightest star in Orion. The Greek alphabet of 5 magnitudes therefore corresponds to a dif
point (longitude = 0°; latitude = 0°) is the direc is listed below. ference in apparent brightness of exactly 1 00
tion of the centre of the Milky Way Galaxy. In the early 18th century, the English astron times. We can also write 1st magnitude as 1m,
omer John Flamsteed (1646-1719) gave consecu 2nd magnitude as 2m, etc. Intermediate bright
tive numbers to stars in each constellation, or nesses are expressed with decimals, for instance
NAMES AND DESIGNATIONS dered by R.A.; for instance, Betelgeuse was" 58 1 '?5. The brightest star in the sky, Sirius, has
Ori" in his system. an apparent magnitude of -1.6. It is 7.6 magni
The brighter stars bear intriguing names like Be However, most astronomical objects do not tudes, or about 1100 times, brighter than the
telgeuse, Canopus and Pollux. Many of them can carry names but only designations which origi faintest stars that can be seen with the unaided
be traced back to antiquity and relate to Greek nate in some catalogue, compiled by patient and eye, and which are of magnitude 6. The faintest
or Roman mythology, and others are of Arabic persistent observers. The objects in this book objects that can be observed with large telescopes
origin. For instance, Betelgeuse is a corruption have designations from the following astronomi are of magnitudes 25-26.
of the Arabic "yad al-jawza", the hand of Orion. cal catalogues (see also the Glossary): A relatively faint object close to us may have
Canopus is a Greek proper name with Egyptian the same apparent brightness as a luminous ob
M Messier Catalogue (1771-1782)
roots and Pollux is the latinized name of a char ject further away. An important, but difficult as
NGC New General Catalogue of Nebulae and
acter in Greek mythology, the twin of Castor. pect of astronomical research is to determine the
Clusters of Stars (1888)
Quite a few of the non-stellar objects described luminosity of an object, that is the total amount
IC First and Second Index Catalogue
in this book have descriptive names like the" Or of radiation it emits per unit of time. It is com
(1895, 1908)
ion Nebula", the "Antennae galaxies", etc. See mon to compare other stars to the nearest one,
HR Bright Star Catalogue (4. Ed., 1982)
also Table 1 in the Index of Objects (p. 271). our Sun. A frequently used astronomical unit
HD Henry Draper Catalogue
From ancient times, the sky has been divided is therefore a Solar Luminosity, which is the
(1918-1924)
into constellations, that is groupings of bright amount of energy radiated by the Sun per sec
ESO ESO/Uppsala Survey of the ESO(B) At
stars that seem to form figures and symbols in ond. The luminosity of a star depends on its
las (1982)
the sky. Different cultures have divided the sky temperature and its radius. Another astronomi
in different ways and a great variety of constella Tables 2 and 3 of the Index of Objects contain cal unit is a Solar Mass. The heaviest known
tions are known in historical sources. The 89 all the objects mentioned in this book, ordered stars have masses of about 100 solar masses.
constellations that are now in use were defined by Messier and NGC/IC numbers, respectively. In astronomy, earthly units of measurement
by the International Astronomical Union in often turn out to be inconvenient. For instance,
1923. distances are usually expressed in Light-years or
Bright stars are often referred to by the con BRIGHTNESS, LUMINOSITY, MASS AND DISTANCE Astronomical Units. One light-year is the distance
stellations to which they belong. For instance, which is travelled in one year by light at a speed
the brightest star in the constellation of Centaur The apparent brightness of an astronomical ob of 300000 km/sec. A light-year may be divided
us is Alpha Centauri, and the second brightest ject is the brightness with which we see it in the into light-days or light-minutes. On this scale,
is Beta Centauri. The short forms are r:x Cen and sky. It is common to express the apparent bright for example, the mean distance between the Sun
f3 Cen. This nomenclature was first introduced ness in magnitudes, a system which was first in and the Earth is 8.2 light-minutes. This distance,
by the German astronomer Johann Bayer troduced by the Greek astronomer Hipparchos 150 million km, is also referred to as one astro
(1572-1625) who based his system on observa (died in 125 B.C.), but defined in modern terms nomical unit, which is mainly used in descrip
tions done by his contemporary Danish col in 1857 by the English astronomer Norman R. tions of the Solar System.
league, Tycho Brahe (1546-1601). In those pre Pogson (1829-1891). According to this system, It is difficult to determine distances outside
telescopic days, errors were made and f3 Ori (Ri a star of 1st magnitude is V100",2.512 times the Earth, and most astronomical distance mea
gel), not r:x Ori (Betelgeuse), as one would expect, brighter than a 2nd-magnitude star. A difference surements are not very accurate, at least by com-
3
mon standards. The distances to the nearest All material bodies, stars and nebulae in ASTRONOMICAL UNITS
stars, around 4 light-years, are known with an cluded, emit electromagnetic radiation. Depend
accuracy of 1-2%, but with increasing distance, ing on the wavelength, this radiation is known 1 Astronomical Unit = 1.496 x 108 km
the achievable precision rapidly deteriorates. by different names, as radio, microwave, infrared, 1 Light-year =9.461 x 1012 km
Methods of distance determination are men optical or visual, ultraviolet, X-ray and y-ray, 1 Angstrom (A) =1O-10 m
tioned in connection with Plates 6, 37 and 124. when we move through the spectrum from the 1 Solar Luminosity = 3.9 x 1026 Watt
The apparent brightness of an object depends longest to the shortest wavelengths. Since a 1 Solar Mass = 1.989 x 1030 kg
on its luminosity and distance. It decreases with shorter wavelength corresponds to more energet
the square of the distance, so that if we were ic radiation, y-rays are more energetic than X
to move an object to twice its present distance, rays, and ultraviolet radiation is more energetic GREEK ALPHABET
its apparent brightness would become four times than infrared radiation. Hot objects are more
less; at three times the distance, it would be nine energetic than cold ones and therefore radiate Acx Alpha Nv Nu
times less, etc. In other words, if we know the more energy in the short-wavelength region. For BfJ Beta E~ Xi
ry
apparent brightness and the luminosity of an ob example, a star that is hotter than the Sun emits Gamma 00 Omicron
ject, we can calculate its distance; if we know more ultraviolet radiation than does the Sun. In L1<5 Delta iln Pi
the apparent brightness and the distance, we can the visual region, blue light has a shorter wave E8 Epsilon Pp Rho
calculate the luminosity. Note, however, that this length than green light, and green light in turn Z( Zeta ,EO' Sigma
is only true if there is no obscuring material be has a shorter wavelength than red light. HYf Eta Tr Tau
tween us and the object. Atoms radiate at specific wavelengths (spec 89 Theta Yv Upsilon
tral lines). The observation of spectral lines in Il Iota l/>rp Phi
the light of a star therefore indicates the presence KK Kappa Xx Chi
TEMPERATURE AND SPECTRUM of the corresponding atoms in the outer layers AA Lambda 'P1jI Psi
of that star. One of the most common spectral Mil Mu Qw Omega
In daily life, we measure temperatures in °C or lines in the light of interstellar nebulae is the
OF. In astronomy, temperatures are expressed in so-called" H" "-line, which is emitted by hydro
degrees Kelvin (K), that is degrees above the ab gen atoms in the red region of the spectrum with
solute zero at - 273°C. The stars have different a wavelength of 6563 A.
surface temperatures. A common stellar classifi When an atom loses one or more electrons,
cation system corresponds to the temperature it is said to become ionized. Regions in space
scale: O-stars are the hottest (100000 K), then with much ionized hydrogen (" H II regions")
follow the B-stars, the A-stars and the F-stars. are seen as "emission nebulae", which emit
The Sun (5800 K) is of type G, the K-stars are strongly in the spectral lines of various ions and
cooler and the coolest are of type M (3000 K). atoms, including the H,,-line. When the tempera
ture is high enough, oxygen atoms may lose one
electron and emit strongly in blue light. At even
higher temperatures, two electrons are lost from
each oxygen atom and the oxygen ions now emit
in two green spectral lines. This book contains
many examples of nebulae that show these col
ours.
4
1 The Universe and
its Galaxies
5