A Brief Look at a Mid-20th Century Classic: “The Larousse Encyclopedia of Astronomy.”

Packed full of beautiful drawings: the Larousse Encyclopedia of Astronomy(1966 edition).

As I’ve explained many times before, I value the printed word. When I’m looking for information, I generally lean towards authors that have a proven track record in a given discipline, rather than spending hundreds of hours on an online forum to find specific answers to questions. These are and have always been my ‘authorities’. By carefully studying the astronomical literature of the past, I have discovered many facts that the modern forum user has not known, let alone considered. Many of these discoveries are presented in my new historical work, Chronicling the Golden Age of Astronomy. That said, knowledge is never fixed; there is always something new to learn! And so, I have turned to what I consider to be a classic astronomy text of the mid-20th century; The Larousse Encyclopedia of Astronomy, to get a better insight into what people of science had learned in the human generation immediately preceding my own.

The Larousse Encyclopedia of Astronomy first came off the printing press back in 1959, in a unique collaboration between the French professional astronomer, Gérard Henri de Vaucouleurs (1918–1995) and his compatriot, the distinguished amateur astronomer and artist, Lucien Rudaux(1874-1947). It was a match made in heaven, for this superb fusion of art and science enjoyed a number of reprintings, first in 1962 and finally in 1966. The edition I discuss here was published in 1966, which included an introduction written by the distinguished American astronomer, Fred L. Whipple(1906-2004) of comet fame.

The Title Page.

My personal copy of this work was acquired somewhat serendipitously, when, during my year at the University of Strathclyde, Glasgow, studying for my Post-Graduate Certificate in Physics Education(2000-2001), I was offered this book after it was discontinued by the University library. What’s more, it was going free to a good home! How could I refuse? What I got was a beautiful, large tome, with a durable and strong cloth-over-board cover, and in excellent general condition.Neat!

The beautiful, cloth-over board cover of the Larousse Encyclopedia of Astronomy.

The book was conceived of right at the beginning of the space age, when Mankind triumphantly declared his conquest of outer space. No longer dependent on idle speculation, the authors aimed to show the reader that modern astronomical science had finally brought the heavens down to Earth. No longer were the stars, galaxies, planets and their Moons pie in the sky abstractions; these were places every bit as real as the ground beneath our feet!

Imagine my surprise when I first started combing through its thick pages only to discover that this work was not, in fact, an encyclopedia, at least in the normal sense of the word! The contents page ought to have alerted me to this;

The title page.

The contents page reveals the non-encyclopedic nature of the work.

Instead, the work is divided into 4 sections or ‘books,’ which include;

Book I: The Splendour of the Heavens

Book II: The Empire of the Sun

Book III: The Realm of the Stars

Book IV: Astronomical Instruments and Techniques

Book I: The Splendour of the Heavens

Book I, which has two chapters, deals with the elements of physical astronomy and is wonderfully illustrated throughout. It provides the reader with a basic, albeit solid grounding in how the sky works. This is classical knowledge, as true today as the day it was penned. Take a look at some of the drawings and diagrams used to illustrate these chapters:

The Earth from space.

A rapidly disappearing vista; the majesty of the Milky Way from a dark country site.

Some of the conic sections; the circle, ellipse and parabola.

Kepler’s second law of planetary motion, illustrating the concept of equal areas in equal times.

The realm of the galaxies.

Book II Empire of the Sun

Many classic stories are recounted in the text, including the once seriously considered planet Vulcan, thought to orbit the Sun closer in than Mercury. There is even a diagram showing the hypothetical orbit as envisioned by the great French astronomer, Urbain Le Verrier(1811-1877).

The hypothetical orbit of the planet Vulcan( denoted by a ‘V’) as imagined by Le Verrier.

We are prone to forget that the Earth is a planet in its own right but the Larousse Encyclopedia we get an exquisite overview of the many and various meteorological phenomena that make our world so spectacular.

Check out this page showing the kinds of clouds that grace the Earth’s atmosphere at various altitudes;

Earth’s cloud systems.

Moving on to our nearest neighbour in space, the Larousse excels with some fine, high- resolution images of the lunar regolith. What may surprise a few readers is that some very detailed lunar images were made using the 100-inch Hooker reflector atop Mount Wilson. This giant eye on the sky is far more famous for the seminal contributions it made to cosmology, especially Edwin Hubble’s discovery that the Universe is expanding. The photographs really don’t do proper justice to the actual quality of the images reproduced in the work, but will nonetheless serve our purposes here;

The first quarter Moon as imaged by the 100-inch reflector on Mount Wilson.

An amazingly detailed image of the Lunar Apennines, the great crater Copernicus, Caucasus and the Lunar Alps, as photographed by the 100-inch Hooker reflector.

The authors are unusually aware of perspective. For example, have a look at this figure, which shows the size of the British Isles in comparison to the size of the Moon.

An amusing lesson in scale: the Britsih Isles superimposed on the full Moon.

Chronicling also features a detailed chapter on the Great Meudon Refractor, located just outside Paris, which once represented the brain and glory of late 19th and early 20th century French astronomical science. The reader of Larousse will be in for quite a treat in the chapter covering the planets, as many of the exquisite drawings came directly from the French tradition. As well as drawings made by Rudaux, who was inspired by the eccentric French astronomer, Camille Flammarion(1842-1925) there are also exquisite renderings from de Vaucouleurs, who made use of a fine 8 inch classical refractor based at Houga Observatory(founded in 1933 by the amateur astronomer and electrical engineer, Julien Peridier), France, during the late 1930s and early 1940s. Many other planetary sketches were made by distinguished French observers such as Bernard Lyot,  H. Camichel and M. Gentili, making use of a superb 15 inch refractor at the Pic du Midi Observatory in the French Pyrenees.This Observatory, which is still alive and well, attracts some of the finest planetary imagers in the world (including the UK’s Damien Peach) who have produced some of the best CCD images of the major planets yet taken from the Earth, owing to the superb astronomical seeing manifested at this high-altitude site.

The relative sizes of the planets as seen through the telescope.

It is clear that while great strides had been made in the improvement of astronomical photography of the planets since the early 20th century, they were still not the equal of visual drawings made by trained observers. Larousse reflects this situation most convincingly.

Elusive markings on little planet Mercury.

Some of the drawings of the Cytherean disk featured in Larousse certainly display atmospheric details that we would consider largely illusory today.

Somewhat dubious atmospheric features of Venus.

The section on the planet Mars is partcularly interesting. As the drawings made in 1941 reveal below, even professsional astronomers like de Vaucouleurs were still actively engaged in visual observations;

A series of Martian disk drawings made by de Vaucouleurs in 1941 using an 8 inch refractor at Houga Observatory.

That such work was still being conducted during a time when the Nazis occupied France is all the more remarkable!

Part of the training of these visual observers involved recording detail from artificial Martian disks, such as the one illustrated below. The image on the top left represents a close up of an articial disk, whereas the image on the top left is a photograph of the same artificial disk taken at the same resolution as the human eye with the telescope.The bottom two images represent sketches of the artificial disk as recorded by two separate observers. One can see that while good objective agreement can be achieved with such tranining, there still exists significant inter-individual differences between the details recorded.

The planetary observers of the era used articial disks to hone their visual skills.

By the mid-20th century, astronomers were beginning to use different parts of the electromagnetic spectrum to explore the Martian orb. The figure below shows two such images; one in infrared(right) and the other at UV wavelengths(left), captured by the astronomers at the Lick Observatory, USA.

Mars as imaged in the ultraviolet( left) and infrared(right).

Both the chapters on the Moon and Mars have discussions on whether life might have or could still exist on these bodies. Predictably, the fabled Martian canals are discussed at some length and the conclusions drawn by the authors seem to still hold a candle for there being life on the Red Planet. Thus, even by the mid-20th century, some planetary observers were still seriously entertaining such outlandish ideas. Of course, this was a time when living creatures were considered to be very much part of the natural order, as “inevitable” as sand grains, rocks and suns; a view that is being rapidly overturned today by the unceasing march of science.

The fabled Martian canals by Douglass(Lowell Observatory).

Still, the fecund imaginings of Rudaux are also on display in the Martian chapter. Decades before any spacecraft landed on the Red Planet, he produced an uncannily real depiction of the Sun about to set beneath the Martian horizon;

Sunset on the Red Planet. Note its smaller size in comparison to a terrestrial sunset.

From Mars, the authors continue on to discuss the fascinating asteroid belt before venturing on to my favourite world; Jupiter. As the drawings in the opening image of this blog reveal, this world shows up a wealth of detail to the keen telescopist armed with an instrument of modest aperture. The authors do a superb job of capturing the dynamism of this gas giant in all its glory:

Things change fast on mighty Jove; as these drawings reveal, taken just one hour apart.

The French planetary astronomers of this era spent a considerable amount of time learning about the nature of the four giant satellites that circle Jupiter, recording with great attention to detail, many of their many kinematic interactions, particularly transits and eclipses( mutual or otherwise);

Drawings showing some fascinating aspects of Jupiter’s large satellite system.

On the best nights of astronomical seeing, the French planetary astronomers made significant strides in recording many of the main albedo features of the Galilean satellites. The reader will note that these visual observations are exceedingly difficult to conduct, owing to the tiny angular diameters they subtend, requiring large aperture, ultra-high magnifications and good air in equal measure to do any justice to them;

Full disk drawings of the Galilean satellites as recorded by Eugene M. Antoniadi(top plate) using the 33-inch Meudon refractor, and those made by Lyot, Camichel and Gentili employing instruments at the Pic Du Midi Observatory(bottom plate).

The section on Saturn is equally engaging, with beautiful artwork showing its majestic features:

A wonderful full-colour drawing of Saturn showing its atmospheric features and majestic ring system.

It was only in the 1930s and 40s that astronomers were beginning to divine the chemical composition of the atmosphere of the outer planets and their satellites. Larousse presents good spectral data of Saturn’s mysterious satellite, Titan, as recorded by the Dutch-American astronomer, Gerard P. Kuiper, showing for the first time that it contained several simple hydrocarbons, such as methane and ethane.

When it comes to the outermost worlds in our solar system, considerable uncertainty was still the rule rather than the exception. For example, planetary astronomers were very unsure as to the size of Pluto, as evidenced by the following illustration:

By the mid-20th century, our scientfic knowledge of Pluto was very uncertain, including its estimated size. Orb C is closest to the modern accepted size.

We now know that Pluto, archetypal of a new class of bodies known as dwarf planets, has a surface area slightly less than half that of our own Moon.

After presenting an excellent overview of comets, Larousse provides an equally fascinating overview of meteors and meteorites; pieces of heaven that end their lives in Earth space:

Artistic rendition of the radiant of a spectacular meteor storm occurring on the night of October 9 1933.

Moving on to discuss our star, the Sun, Larousse provides a detailed exposition of our knowledge of the Sun and shows that solar scientists had developed technologies that enabled them to see phenomena that hitherto were quite invisible to human eyes.

For example, Larousse presents a remarkable sequence of photographs showing the evolution of a solar prominence:

A sequence of solar prominences as recorded on June 18 1929.

It even shows how astronomers were using narrow band imaging techniques to capture solar images at wavelengths centred on the Calcium K line and the Hydrogen alpha line:

Solar astronomers at Meudon Observatory were developing narrow band imaging techniques. Left hand column represents Calcium K line spectrograms, while the right hand column shows a sequence of H alpha images.

Indeed, these narrowband imaging techniques are now used by amateur solar astronomers across the world.

Book III: The Realm of the Stars

This section of the encyclopedia discusses the stars as suns. And while it is not possible to gain a full knowledge of stellar physics without treating it mathematically, the authors do a great job of explaining difficult physical phenomena in layman’s terms. The section on the nuclear physics of stellar interiors is very impressively conveyed in this volume. But there are also wonderful nuggets of information that you only infrequently encounter in other texts. For example, Larousse presents a very useful table showing the degree to which starlight is extinguished as a function of altitude;

The degree of attenuation in stellar brightness as a function of altitude.

One consequence of this attenuation of stellar brightness as altitude decreases is that we can never experience the full glory of bright stars or deep sky objects if  they remain close to the horizon. From my own location at 56 degrees north latitude, the maximum elevation of the celestial equator will be 90-56 = 34 degrees. Now, consider the bright star Sirius, whose declination is ~ -17 degrees, its maximum altitude above my southern horizon is 34 +(-17) = 17 degrees. From the table above, we see that the apparent brightness of Sirius will be a full half magnitude lower than it would appear at altitudes above 45 degrees or so. This is also true of deep sky objects. For instance, I became acutely aware of this effect as I followed the bright globular cluster M13 with my 12″ f/5 Dob during late March and much of April. Before midnight, the view was rather disappointing as the cluster was then at a low altitude in the east. I would often wait until the wee small hours of the morning to let the cluster rise as high as possible in the sky in order to achieve the best possible view. The change in the cluster’s appearance was quite striking from hour to hour but it was definitely worth the wait!

After discussing the stars, their brightness, and distribution across the heavens, Larousse presents excellent chapters on both variable and multiple stars systems that are as valid today as they were when first written. Some of the most visually stunning, colour contrast binary systems are presented in a beautiful colour plate shown below:

Beautiful artistic renderings of some of the skies most celebrated double stars.

After discussing the stars, the authors move on to consider the Milky Way Galaxy as a whole, as well as the vast reaches of intergalactic space. Here, yet again, we are presented with stunning black & white images of a variety of objects both within and far beyond our own ‘Island Universe’;

The Great Globular Cluster M 13, in Hercules as photographed by the 60-inch reflector atop Mount Wilson in 1910. The exposure was made over several nights in June and the resulting star count amounted to 40,520 !

The 20th century wrought new technologies that helped astronomers delineate the fine details of our own galaxy’s spiral arms. Larousse presents early data collated by astronomers using the 21cm microwave hydogen emission line:

Tracing the nearby structure of the Milky Way’s spiral arms centered on the Sun((marked with an x) using the hydrogen 21cm microwave emission line.

In this regard, the pioneering work of the Dutch astronomer, Dr. Jan Oort(1900-1992), of Leiden Observatory, is discussed in detail.

Larousse presents many stunning monchrome images of celebrated galaxies like this one of M 51, the famous Whirlpool Galaxy in Canes Venatici:

M51 and its companion galaxy, as photographed by the 100 inch Hooker reflector atop Mount Wilson. a 3 hour exposure made on the evening of May 15 1926.

By the mid-20th century, astronomers had discovered that the Universe was in a state of expansion with many more distance measurements of galaxies added to Edwin Hubble’s pioneering list. This helped astronomers refine the value of the Hubble constant (Ho), the reciprocal of which provided the age of the Universe. Back then, of course, there was still considerable uncertainty regarding the precise age of the cosmos but Larousse entertains timescales of the order of 5 billion years, in agreement with upper bounds established by the half lives of the most long-lived radionuclides.

In a chapter entitled Past and Future, the authors discuss the concept of stellar and galactic evolution in more or less its modern sense of the word. It also introduces some basic cosmology.

Stellar evolution as portaryed by a Hertzsprung-Russell Diagram.

There is no mention of dark energy or dark matter, of course, since these were not postulated at the time. Still, the reader can gain a fairly accurate education on some of the big questions astronomers and cosmologists were asking in the middle of the 20th century.

Book IV: Astronomical Instruments and Techniques

In this, the last section of Larousse, we learn of the magnificent ingenuity of scientists and engineers of yesteryear in designing what was then, state-of-the-art astronomical equipment. The encyclopedia is lavishly illustrated with wonderful old photos of classic telescopes including some giant ones, such as the 100-inch Hooker reflector on Mount Wilson and the venerable 40-inch Clark refractor at Yerkes Observatory, the latter of which I discuss in relation to double stars (Aitken) and planetary observing(E.E. Barnard)  in Chronicling;

The wonderful 100-inch Hooker reflector while in active service. It has now been retired from professional use.

The largest refractor ever built; the 40-inch Clark at Yerkes Observatory.

This section discusses the details of using old photographic emulsions, micrometers, photometers and many other scientific instruments that were part of the workanight instrumentation of the pros of that era. Computers were still in their infancy in those days and so their users still had to resort to doing much of their work by hand.

The business end of a 15-inch refractor used for double star mensuration.

The basic principles of radio astronomy is covered at the end of Larousse, including an early picture of Jodrell Bank Observatory;

The gigantic steerable radio telescope at Jodrell Bank, Manchester, UK, which was newly dedicated in 1945. This author reckons Sir Bernard Lovell is the character seen seated in the control room(top image).

Well, I hope you enjoyed this brief overview of a now classic text. I for one feel very privileged to have acquired it both for educational and sentimental reasons. Larousse is part of our shared astronomical heritage, and will continue to take a good place in my own ibrary. And while modern re-prints are available, it’s nice to have an original copy.

They certainly don’t make tomes like this any more!

Thanks for reading.


If you like this work, please support me by considering my new book on the history of our science over four centuries, Chronicling the Golden Age of Astronomy.


De Fideli.

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