Max Wolf

German astronomer

• Born: June 21, 1863
• Birthplace: Heidelberg, Baden (now in Germany)
• Died: October 3, 1932
• Place of death: Heidelberg, Germany

Wolf was the first astronomer to use an astronomical camera to discover asteroids by combining the camera with a mechanical telescope. During his very full career, Wolf discovered 582 asteroids with 228 of these receiving general recognition. This figure is a personal record of discoveries in astronomy that has been difficult to surpass.

Early Life

Max Wolf (vohlf) was the son of Franz Wolf and Elise Halwerth. He was attracted to astronomy at an early age and, while a student at Heidelberg, erected his own small observatory. Since his father was a wealthy physician, Wolf was able to afford this private facility. In 1884, he discovered the comet that bears his name. This discovery so fired his interest in astronomy that he gave up all of his other studies to pursue a career in this field, earning a Ph.D. from Heidelberg with a dissertation in celestial mechanics.

In 1891, Wolf discovered his first asteroid, using photography. For this discovery, he was awarded the Lalande Prize of the Paris Academy of Sciences. After a visit to the United States, during which he received financial support for a sixteen-inch double telescope, Wolf returned to Heidelberg to work with the grand duke of Baden to build a new observatory at Königstuhl. In 1893, Wolf was named director of this new observatory and, simultaneously, became extraordinary professor of astrophysics at the University of Heidelberg. In 1902, he was elected to the chair of astronomy at the same university. Wolf remained at Heidelberg for the rest of his life, discovering his last asteroid, 1219 Britta, there only a few months prior to his death.

Life’s Work

Wolf had two major accomplishments during his career. The first was the use of an astronomical camera in connection with a telescope to hunt for asteroids. To accomplish this search, the telescope was centered on a conveniently located bright star. The clockwork of the telescope kept track with the movement of the star so that photographs showed the star as a dot of light. Asteroids and comets moving across the field around the star would appear on the photograph as lines. Visual observation with the telescope alone would then determine whether the line was a comet or an asteroid. Because the clockwork drive for telescopes was not entirely accurate, the photographic session had to be monitored constantly to keep the star in the crosshairs of the telescope. Wolf developed the technique for this method of sky search to a high degree. His methods were adapted widely by other astronomers.

The second great accomplishment of Wolf’s career was the discovery of the Trojan asteroids, a large number of asteroids outside the asteroid belt and in the orbit of Jupiter. In 1906, Wolf observed an asteroid, which he called Achilles, whose orbit seemed unusual. Mathematical computations showed that Achilles was in the orbit of Jupiter. Although this seems impossible, an eighteenth century mathematician, Joseph-Louis Lagrange, had determined that, in theory, a small object can travel in the same orbit as a large object if the two objects and the sun form an equilateral triangle. To do this, the small object must be about sixty degrees ahead of or behind the large one. Wolf was searching sixty degrees ahead of Jupiter when he discovered Achilles. The name “Achilles” was chosen by Wolf because other asteroids had feminine names, but this one was outside the asteroid belt.

The discovery of Achilles suggested that one should search sixty degrees behind Jupiter, and there other bodies were found. The first of these was named Patroclus. This established a pattern; all these asteroids were named for heroes of the Trojan War, and the two groups are collectively called the Trojan asteroids. All of those in the Achilles group, except one, Hector, are named for the Greeks, and, except for Patroclus, the second group are named for the defenders of Troy. Some seven hundred Trojan asteroids have been identified.

Significance

By combining the best technology of his time with accepted theories, Wolf was able to demonstrate the factuality of the Lagrange theory with respect to Jupiter. No other planets have asteroids at the Lagrange points of sixty degrees ahead or behind. By demonstrating an effective method of searching for asteroids, Wolf advanced early twentieth century knowledge of astronomy. The technology of astronomy of the late twentieth century has led to so many asteroid discoveries that one astronomer has called them “vermin of the skies.” In Wolf’s day, they were a new and exciting field of observation and discovery.

Bibliography

Aguirre, Edwin. “A Flaming Runaway Star.” Sky and Telescope 109, no. 4 (April, 2005): 32-33. Describes IC 405, which Wolf called a flaming star.

Croswell, Ken. “The Blue Witch.” Sky and Telescope 113, no. 4 (April, 2007): 26-27. Discusses the colors of interstellar nebulae, including the Witch Head Nebulae discovered by Wolf.

Cunningham, Clifford J. “The First Planetarium.” Mercury 34, no. 5 (September/October, 2005): 10. A brief history of the modern planetarium, which originated in 1913 when Wolf suggested the creation of a planetarium to be installed at a museum in Munich.

Freiesleben, H.-Christ. “Maximilian Franz Joseph Cornelius Wolf.” In vol. 14 of Dictionary of Scientific Biography, edited by Charles Coulston Gillispie. New York: Charles Scribner’s Sons, 1976. This reference work has a biographical sketch of Wolf and includes a short bibliography of his astronomical articles, most of which are in German and are untranslated.

Gehrels, Tom. Asteroids. Tucson: University of Arizona Press, 1979. This textbook on asteroids has several references to Wolf and his work. It explains the significance of asteroids in the planetary scene.

Kowal, Charles T., ed. Asteroids: Their Nature and Utilization. New York: John Wiley & Sons, 1988. Kowal describes Wolf’s discovery of the Trojan asteroids and discusses the Lagrange theory in layperson’s terms.

Mitton, Simon, ed. The Cambridge Encyclopedia of Astronomy. New York: Crown Books, 1977. A basic reference work, this book has good articles on asteroids and the Trojan asteroids. Includes a brief biographical sketch on Wolf that focuses on his work.

Vaucouleurs, Gérard Henri de. Astronomical Photography: From the Daguerrotype to the Electron Camera. New York: Macmillan, 1961. A history of asteroid photography. Contains numerous references to Wolf’s work and several photographs and charts of asteroids.