Abstract
Between 1761 and 1776, Christian Horrebow made regular observations of sunspots from Rundetårn in Copenhagen. Based on these observations he writes in 1775 that “it appears that after the course of a certain number of years, the appearance of the Sun repeats itself with respect to the number and size of the spots”. Thus, Horrebow hypothesized the idea of a cyclic Sun several decades before Heinrich Schwabe discovered the solar cycle and estimated its period. This proves the ability of Horrebow as a sunspot observer. In this article, we present a general overview of the work of Christian Horrebow, including a brief biography and a complete bibliography. We also present a translation from Danish to English of his writings on sunspots in the Dansk Historisk Almanak. These writings include tables of daily sunspot measurements of which we discuss the completeness.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
Notes
Original: Schon aus meinen früheren Beobachtungen, die ich jährlich in dieser Zeitschrift mittheile, scheint sich eine gewisse Periodicität der Sonnenflecken zu ergeben und diese Wahrscheinlichkeit gewinnt durch die diesjährigen noch an Sicherheit.
Original: (...) dog lader det til, at visse Aars Forløb kommer samme Solens Skikkelse igien i Henseende til Mængden og Størrelsen af Pletterne, og ligeledes bliver det i Tiiden værdt at lægge Mærke til, om ikke Pletternes Tal i Solen og Størrelsen haver nogen Indflydelse paa Luftens Tilstand hos os paa Jorden.
References
Arlt, R.: 2008, Digitization of sunspot drawings by Staudacher in 1749 – 1796. Solar Phys. 247, 399. DOI . ADS .
Bugge, T.: 1784, Observationes Astronomicae Annis 1781, 1782 and 1783. ADS .
Clette, F., Svalgaard, L., Vaquero, J.M., Cliver, E.W.: 2014, Revisiting the sunspot number. A 400-year perspective on the solar cycle. Space Sci. Rev. 186, 35. DOI . ADS .
Gyldenkerne, K., Darnell, P.B.: 1990, Dansk astronomi gennem firehundrede år.
Horrebow, P.: 1735, Basis astronomiae sive astronomiae pars mechanica in qua Danica; simulque eorundem usus, sive methodi observandi Roemerianae describuntur observatoria, atque instrumenta astronomica Roemeriana. DOI . ADS .
Hoyt, D.V., Schatten, K.H.: 1995, A new interpretation of Christian Horrebow’s sunspot observations from 1761 to 1777. Solar Phys. 160, 387. DOI . ADS .
Hoyt, D.V., Schatten, K.H.: 1998, Group sunspot numbers: a new solar activity reconstruction. Solar Phys. 181, 491. DOI . ADS .
Karoff, C., Jørgensen, C.S., Senthamizh Pavai, V., Rainer, A.: 2019, Christian Horrebow’s sunspot observations – II. Construction of a record of sunspot positions. Solar Phys. DOI .
Muñoz-Jaramillo, A., Vaquero, J.M.: 2019, Visualization of the challenges and limitations of the long-term sunspot number record. Nat. Astron. 3, 205. DOI . ADS .
Schwabe, H.: 1844, Sonnenbeobachtungen im Jahre 1843. Von Herrn Hofrath Schwabe in Dessau. Astron. Nachr. 21, 233. DOI . ADS .
Svalgaard, L.: 2017, A recount of sunspot groups on Staudach’s drawings. Solar Phys. 292, 4. DOI . ADS .
Svalgaard, L., Schatten, K.H.: 2016, Reconstruction of the sunspot group number: the Backbone method. Solar Phys. 291, 2653. DOI . ADS .
Thiele, T.N.: 1859, De Macularum Solis antiquioribus quibusdam obstervationibus Hafniae institutis, scripsit Th. N. Thiele, astr. stud. Astron. Nachr. 50, 257. DOI . ADS .
Usoskin, I.G., Kovaltsov, G.A., Lockwood, M., Mursula, K., Owens, M., Solanki, S.K.: 2016, A new calibrated sunspot group series since 1749: statistics of active day fractions. Solar Phys. 291, 2685. DOI . ADS .
Vaquero, J.M., Svalgaard, L., Carrasco, V.M.S., Clette, F., Lefèvre, L., Gallego, M.C., Arlt, R., Aparicio, A.J.P., Richard, J.-G., Howe, R.: 2016, A revised collection of sunspot group numbers. Solar Phys. 291, 3061. DOI . ADS .
Wolf, R.: 1873, Astronomische Mittheilungen XXIII. Astron. Mitt. Eidgenöss. Sternwarte Zür. 4, 77. ADS .
Acknowledgements
We would like to thank the referee for thoughtful comments which significantly improved the paper. The translation of Christian Horrebow’s published papers on sunspots was done by Lenore Messick, Events and Communication Support, Aarhus University. The project has been supported by the Villum Foundation. Funding for the Stellar Astrophysics Centre is provided by the Danish National Research Foundation (grant agreement no. DNRF106), funding for VSP is provided by the Deutsche Forschungsgemeinschaft (grant no. AR355/12-1). We are very grateful to Susanne Elisabeth Nørskov, who has been most helpful throughout the project with finding the notebooks and other historical texts. We are also grateful to Kristian Hvidtfelt Nielsen, who helped with interpreting the historical texts.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Disclosure of Potential Conflicts of Interest
The authors declare that they have no conflicts of interest.
Additional information
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Electronic Supplementary Material
Below are the links to the electronic supplementary material.
11207_2019_1465_MOESM3_ESM.pdf
Translation of Christian Horrebow’s writings in Skrifter son udi Kiøbenhavnske Selvskab af Lærdoms og Videnskabers Elsker, Tidende Deel (PDF 5.7 MB)
Rights and permissions
About this article
Cite this article
Jørgensen, C.S., Karoff, C., Senthamizh Pavai, V. et al. Christian Horrebow’s Sunspot Observations – I. Life and Published Writings. Sol Phys 294, 77 (2019). https://doi.org/10.1007/s11207-019-1465-z
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s11207-019-1465-z