Early Asteroid Research in Austria

Rudolf Albrecht*
Space Telescope European Coordinating Facility
European Southern Observatory
Karl-Schwarzschild Str. 2
D-85748 Garching, Germany

Rudolf.Albrecht@eso.org

Hans-Michael Maitzen, Anneliese Schnell
Institute for Astronomy
University of Vienna
Türkenschanzstr. 17
A-1180 Vienna, Austria

maitzen@astro.univie.ac.at, schnell@astro.univie.ac.at

*) Affiliated to the Astrophysics Division, Space Science Department, European Space Agency

Abstract

Johann Palisa discovered the first asteroid (136) Austria) in 1874 at the Austrian Naval Observatory in Pola, Istria. After discovering 27 more objects in Pola, Palisa was offered a position in Vienna where he had the new large refractor (at that time the largest telescope in the world) at his disposal. During his career he discovered a total of 121 asteroids, making him the most successful discoverer of minor planets using visual techniques.

Joseph Rheden used the new technology of photography to continue the program. He concentrated on measurements of positions for the purpose of orbit determination. At the same time Theodor Oppolzer introduced a new method of orbit determination which was applied to the observations.

International cooperations resulted among other projects in the production of the Wolf-Palisa charts, and, much later, in a remeasurement of the original plates and use of the data for the improvement of orbit determination.

This successful field of research came to an end because of the deterioration of observing conditions in Vienna, financial problems due to the political and economic decline following World War I and the death of Palisa in 1925.



The science of astronomy has a long tradition at the University of Vienna in Austria. Records show that astronomy has been persued since the middle ages. However, for most of the time the work of the Austrian astronomers was hampered by the lack of suitable telescopes. The largest telescope of the old Vienna Observatory, until the middle of the 19th century located on the roof of the old building of the University near the center of Vienna, had a diameter of only 6 inches. As a consequence astronomers in Vienna turned to other areas of interest; they became specialists in calculating orbits of planets and comets.

During the 19th century Austria was a seafaring nation. To support the navigation of her ships at sea, Austria had, as all seafaring nations had to have, a naval observatory (Fig.1).

Fig. 1: The Austro-Hungarian Imperial Naval Observatory in Pola, Istria
Photograph courtesy of Österreichisches Staatsarchiv

The Austrian Naval Observatory was located in Pola (now Pula) near Fiume (now Rijeka) south of the Istria peninsula along the eastern shore of the Adriatic Sea. Pola was the "Kriegshafen" (literally: war harbour) of the Austro-Hungarian Empire.

In 1871 Johann Palisa (1848-1925) was appointed Director of the Austrian Naval Observatory (Fig. 2). His main area of responsibility was the "time service", i.e. the determination and maintenance of the precise time. While the time service was a necessary and demanding task it is easy to imagine that it was not totally satisfying for a reasearch-oriented person.

Following a suggestion by his teacher Theodor von Oppolzer (1841-1886), Palisa started to observe Minor Planets. Although the telescope was, at 6 inches of diameter, not any more powerful than the telescope in Vienna, the observing conditions were considerably better.

In 1874 he found his first object and named it in honour of the Empire and according to the prevailing naming conventions, (136) Austria (Palisa 1874). During his tenure in Pola, Palisa discovered a total of 27 objects. While the discovery of Minor Planets was important to him, he placed even greater importance on the re-observation of objects which had been discovered by others: this was to make sure that good orbits could be determined.

Palisa's mentor von Oppolzer had published a book on orbit calculations (Oppolzer 1870). Based on the "Theoria Motus" (Gauss 1809) he derived useful criteria which allow to decide whether or not an orbit can be determined uniquely from three complete observations (right ascension and declination) at three different epochs. Von Oppolzer calculated orbits and ephemerides for 165 comets and minor planets.

Fig. 2: Johann Palisa (1848 - 1925)

It is interesting to speculate why the then emerging photographic technique was not used. One reason is probably that the lens of the large refractor was optimised for the visual wavelength range, which made it not suitable for the blue-sensitive emulsions of the time (Spitaler 1891). Another reason is presumably the small field of view, which would have necessitated a large number of exposures to cover reasonable areas of the sky.

In any case, Palisa re-observed many of the objects which had been discovered photographically by Max Wolf in Heidelberg, thus assuring the good quality of the orbital elements. The close collaboration with Heidelberg also resulted in the production of the Wolf-Palisa stellar charts. Deep wide-field survey plates, taken in Heidelberg, were converted to high-precision maps in Vienna by superimposing precise coordinate grids. The practical value of these charts for the asteroid observers was that anything in the field of view which was not on the chart was, in all likelihood, a minor planet, a fact which usually could be substantiated by re-observation during the same night, or during following nights. A total of 210 star charts, covering the area around the ecliptic, were published. Production of the charts was discontinued after the First World War, because the prevailing international conditions made it impossible to sell the product.

In 1907 the "Normalastrograph" (plate scale 1 arcmin per mm, lens optimized for blue sensitive plates) was put in operation at the Vienna Observatory. Joseph Rheden (Fig. 3), Palisa's son-in-law, used it to continue the observations of Minor Planets and of comets (Rheden 1913).

He concentrated on the determination of positions for the purpose of orbit determination. Approximately 1000 of the plates taken by Rheden are still in the plate archive of the Observatory. Most of the plates were used for search and discovery, with visual follow-up. Lacking suitable high-precision measuring equipment the plates were not measured at the time. Only in the 1960ies the plates were measured in the framework of a thesis project (Pendl 1969) and the data supplied to the Minor Planet Center (then located in Cincinnati). Accurate determination of positions was carried out and published (Minor Planet Circulars 2698, 2823, 2870, 2907).

Fig. 3: Joseph Rheden (1873 - 1946)

As a consequence of the explosive growth of the city of Vienna around the turn of the century the Observatory had been engulfed by the urban environment. Observing conditions further worsened due to rapid industrialisation and increasing light pollution. During and after the First World War the political and economic situation deteriorated, caused by the breakup of the Austro-Hungarian Empire combined with an economic crisis and hyperinflation, and brought most of the astronomical research in Vienna to a standstill.

The last observations of Minor Planets, which still can be considered a continuation of the original programme, were carried out by Alois Purgathofer (1925-1984), at the occasion of the opposition of the Minor Planet (51) Nemausa in 1954 (Purgathofer 1955).

One of the objects discovered by Palisa, the asteroid (719) Albert, was lost after the initial discovery. Considerable search efforts were made at the time (Palisa 1912, Curtis 1913) and later (Kristensen and West 1989), but the object remained lost. In a remarkable coincidence (719) Albert was recovered by J.A Larsen of the Spacewatch Project (Larsen et al. 2000) several days before this paper was presented.

Acknowledgements

Thanks go to Monika Rode-Paunzen and to Lars Lindberg Christensen.

References

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