A 4.8-inch Fraunhofer refractor telescope, originally used for lunar mapping, became the primary instrument for Samuel Heinrich Schwabe to track the sun from 1826 to 1843. This methodical, seventeen-year quest to locate the hypothetical planet Vulcan led to the empirical discovery of the decadal cycle of solar activity, fundamentally altering the scientific understanding of the star at the center of the solar system.
Pharmacy and Early Studies
Born in Dessau in 1789, Schwabe trained in pharmacy starting in 1806 at the Dessau Mohrenapotheke, owned by his maternal grandfather, Johann H. G. Häseler. He later enrolled at the Humboldt-Universität zu Berlin to study pharmacy under Martin Heinrich Klaproth and Sigismund Friedrich Hermbstädt. However, familial obligations intervened when his grandfather fell ill. Upon Häseler's death in 1812, Schwabe assumed control of the family pharmacy, a business venture that provided significant financial prosperity and allowed him to pursue scientific interests during his spare time.
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In 1825, Schwabe acquired a telescope through a lottery, marking the beginning of his transition toward full-time scientific research. He dedicated himself to locating Vulcan, a theoretical planet believed to orbit between Mercury and the Sun. To identify this elusive body, he recorded sunspot activity daily, believing a transit across the solar disc would reveal the planet. Although he never located Vulcan, his meticulous records eventually comprised 8,486 individual drawings of the solar surface.
Discovery of the Solar Cycle
While documenting sunspots, Schwabe identified a recurring variation in their frequency. In 1843, he published his findings in Astronomical Nachrichten, noting a probable ten-year period during which sunspot activity reached its maximum. Although initial reception was muted, his work caught the attention of Rudolf Wolf, the director of the Bern observatory. This evidence of periodicity is now a cornerstone of solar astronomy, and Schwabe's digitized notes remain a vital resource for analyzing historical solar data.
Botanical and Professional Recognition
Beyond astronomy, Schwabe maintained a significant interest in botany and served as the president of a natural history society in Dessau. Between 1838 and 1839, he authored Flora Anhaltina, a two-volume work documenting nearly 2,000 plant species. His contributions to science earned him the Gold Medal of the Royal Astronomical Society in 1857, presented by Richard Carrington. In 1868, he was elected a Foreign Member of the Royal Society, and he bequeathed his extensive scientific notes to the organization before his death in Dessau in 1875.
Fast facts
- Born: 1789, Dessau
- Died: 1875, Dessau
- Education: Humboldt-Universität zu Berlin
- Field of work: Astronomy, Botany, Pharmacy
- Notable work: Solar cycle
- Award: Gold Medal of the Royal Astronomical Society (1857)
- Membership: Royal Society (Foreign Member, 1868)
Questions readers ask
Did Schwabe find the planet Vulcan?
No. Despite observing the solar disc for seventeen years, he never identified the hypothetical planet.
What was the significance of the 1843 publication?
It provided the first scientific suggestion that sunspot activity follows a regular decadal cycle.
Achievements
- Foreign Member of the Royal Society — 1868
- Notable work: solar cycle
- Educated at Humboldt-Universität zu Berlin
- Fields of research: astronomy
