Astronomy and solar research – Rudolf Wolf and his legacy

Rudolf Wolf (1816 to 1893) was a classical naturalist in the nineteenth century. Born 200 years ago, his broad academic interests, key discoveries, interdisciplinary exchange and diverse publishing and collecting activities still set him apart to this day. 

Astronomer and founder of the Eidgenössische Sternwarte

Wolf celebrated his greatest academic successes as an astronomer. In 1852, he joined other scientists in describing the discovery of the connection between fluctuations of the earth's magnetic field and sunspot activity, demonstrating that a sunspot cycle lasts at least eleven years. Wolf's international acclaim as an astronomer led to his appointment at the newly founded Polytechnic School (now ETH Zurich) in Zurich in 1855, where the architect Gottfried Semper constructed the Eidgenössische Sternwarte according to Wolf's specifications. It served Wolf and his successors as a basis for further solar research and observations.   

First Director at ETH-Bibliothek

As a secondary function, the professor of astronomy was also elected as the Polytechnic School's first librarian – an ideal appointment: not only did Wolf have broad mathematical and scientific expertise; he was also interested in cultural-scientific issues and enjoyed excellent contacts with Switzerland’s naturalist societies, which supported the establishment of the library by donating books. Wolf presented the first printed catalogue (external link) to coincide with the inauguration of the library in January 1856.

Wolf's legacy

Today, rare astronomical works and other purchases or acquisitions from the Wolf era rank among ETH-Bibliothek's most highly sought-after and valuable old holdings. However, Wolf's legacy goes further: today, ETH-Bibliothek safeguards and renders accessible the Collection of Astronomical Instruments, which is also based on Wolf's collecting activities. This also goes for the hundred-year-old series of sunspot measurements that began with Wolf’s systematic solar observations. ETH-Bibliothek makes many of these historically valuable documents and objects accessible online.

Materials on Wolf, astronomy and solar research

Rare Books

Cometa anno 1664 et 1665 observatus à Joh Hevelio

Johannes Hevelii Prodromus Cometicus, 1666, Fig. A [S. 10]
ETH-Bibliothek, Rare Books, Rar 9472 fol.,

  • Works from the collection of Rudolf Wolf
  • Wolf's owner's marks (book plates, stamps, covers)
  • Search in (external link)

Image Archive

Ptolemaic map, 1598

ETH-Bibliothek, Image Archive, Ans_02775-010-PL,

ETH Zurich University Archives

Sunspot drawing no. 10286, 1927

Sketch of spots and torch areas for the investigation of solar activity on 11.02.1927, by William Otto Brunner. ETH-Bibliothek, ETH Zurich University Archives, Hs 1304.2:10323.

  • Unique series of measurements recording sunspots from 1881 to 1995
  • Additional records from the Eidgenössische Sternwarte
  • Information on the current status of the digitization in the project portrait

Collection of Scientific Instruments and Teaching Aids
Graphometer, Michael Butterfield, approx. 1700

ETH-Bibliothek, Collection of Astronomical Instruments, KGS_333-02 (external link)


Literature by and about Rudolf Wolf in the Swiss journals online (external link) in the Knowledge Portal or in E-Periodica (external link).