by David Lechter

While looking through a cornucopia of astronomical images at the Pinterest web site I came across the following image that is actually page 49 of an old book entitled “Smith’s Illustrated Astronomy”(3).

I was able to download a digital copy of the book from (1) and the following quote from the Preface helps explain the purpose of Smith’s book:

“It has been the object of the author of this Illustrated Astronomy, to present all the distinguishing principles in physical Astronomy with as few words as possible; but with such occular demonstrations, by way of diagrams and maps, as shall make the subject easily understood. The letter press descriptions and the illustrations will invariably be found at the same opening of the book; and more explanatory cuts are given, and at a much less price than have been given in any other elementary Astronomy.

This work is designed for common schools, but may be used with advantage as an introductory work in high-schools and academies. In the preparation of these pages most of the best works in our language have been consulted, and the best standard authorities, with regard to new discoveries and facts, have governed the author’s decisions”.

The image follows:

Orbits of the Planets

What struck my eye is that the image shows not only the known planets and some asteroids but their orbital inclinations with respect to the ecliptic. You’ll agree that it is very difficult to read the planets’ names and inclinations recorded in the image; some are relatively clear but some are not. Noteworthy, and difficult to see, is the planet labeled as Herschel, the discoverer of Uranus. William Herschel discovered Uranus in March 13, 1781.

Despite the difficulty in reading the orbital inclinations, a check with Wikipedia(2) shows the image is correct in Smith’s illustration of the planets’ orbital inclinations as seen in Table 1.

Table 1. Inclinations of the Planets (as seen in the image)

Neptune is notably absent in the image. Neptune was observed with a telescope on September 23, 1846 by Johann Gottfried Galle, a director of the Berlin Observatory just three years before the first edition of Smith’s textbook. One can only imagine why Neptune is left out of the image. In fairness to Smith, he does discuss Herschel (Uranus) and Leverrier (Neptune) on page 30. Maybe the image got too crowded or maybe it was an oversight on the artist’s part. We’ll never know I suppose.

We can get a taste of the debate over what to name Herschel’s newly-discovered planet by reading a letter written by Caroline Herschel, William’s sister, to Maria Mitchell and quoted by Dava Sobel in her book on the planets(4). Maria Mitchell, incidentally was an American Astronomer and discoverer of “Miss Mitchell’s Comet”! Caroline’s letter describes how William wanted to name the planet “Georgium Sidus” acknowledging the King’s kindness, while some people in France campaigned for “Planet Herschel”. Sobel mentions that “many other names came forward” too. Herr Bode, director of the Berlin Observatory suggested “Uranus” who “sought safety in mythology”. Sobel notes that sixty years were to pass before the name Uranus was generally accepted. (Incidentally, during this time a German chemist, Martin Heinrich Klaproth, extracted a metal from pitchblende and called it Uranium).

Perhaps we now know why Smith used the name Herschel instead of Uranus in his diagram seen above.

History shows us that continuing studies of ‘Uranus’ a planet with a perturbed orbit led to the discovery of Neptune, a planet that may have been observed by Galileo(5), but was discovered mostly through mathematics!

Sources:

1. Smith’s illustration

2. Orbital inclination

3. Smith, Asa. Smith’s Illustrated Astronomy. New York: Daniel Burgess & Co. 1855.

4. Sobel, Dava. The Planets. New York: Penguin Books, 2005.

5. Neptune