Revisiting Christoph Scheiner's Sunspot Records: a New Perspective on Solar Activity of the Early Telescopic Era

Abstract

Christoph Scheiner was one of the most outstanding astronomers in the history of the sunspot observations. His book, Rosa Ursina, is the reference work regarding the study of the earliest sunspot records. The sunspot observations compiled by Scheiner in Rosa Ursina and Prodomus, including records made by other observers, forms one of the main references of the observations known for that period; particularly around the 1620s. Thus, his work is crucial to determine the solar activity level of the first solar cycles of the telescopic era. The number of sunspot groups recorded in Scheiner's documentary sources has been included in the existing sunspot group number databases. However, we have detected significant errors in the number of groups currently assigned to Scheiner's records. In this work, we reanalyze the information in Scheiner's source documents. Consequently, the standard 11-yr solar cycle shape for the second solar cycle of the telescopic era, which is not clear in previous studies, now becomes evident. In addition, the highest daily number of groups recorded during this cycle (8 groups) is 20% less than the one included in the existing sunspot group number databases. Using the hypergeometrical probability distribution, we find that solar minima in 2008-2009 and 2018-2019 are comparable to the most probable solar activity level of the minimum around 1632. In particular, the estimated lower limit for the solar activity in 1632 is even comparable with the solar activity level in 2008 and 2018.

References in corpus (10)

• Visualization of the challenges and limitations of the long-term sunspot number record
• Solar cyclic activity over the last millennium reconstructed from annual 14C data
• Sunspot area catalogue revisited: Daily cross-calibrated areas since 1874
• Small-Scale and Global Dynamos and the Area and Flux Distributions of Active Regions, Sunspot Groups, and Sunspots: A Multi-Database Study
• Sunspot positions, areas, and group tilt angles for 1611-1631 from observations by Christoph Scheiner
• Sunspot characteristics at the onset of the Maunder Minimum based on the observations of Hevelius
• Strong evidence of low levels of solar activity during the Maunder Minimum
• Number of Sunspot Groups from the Galileo-Scheiner controversy revisited
• Daniel Mögling's sunspot observations in 1626 - 1629: A manuscript reference for the solar activity before the Maunder Minimum
• Sunspot observations by Charles Malapert during the period 1618-1626: a key dataset to understand solar activity before the Maunder minimum

Cited by in corpus (4)

• Re-calibration of the Sunspot Number: Status Report
• Scale Transfer in 1849 : Heinrich Schwabe to Rudolf Wolf
• Temporal and Latitudinal Variation in Penumbra-Umbra Ratios of the Sunspots: Analyses of RGO, Kodaikanal and Debrecen Databases
• Sunspot Observations in 1684-1702: John Flamsteed and Philippe de La Hire