Sunspot Positions and Areas from Observations by Pierre Gassendi
Solar activity behaviour on the eve of the Maunder minimum may provide important information on the period of further suppression of sunspot population. We analyse sunspot positions and areas in the 1630s extracted from rare drawings published by Pierre Gassendi in Opera Omnia. This work was published in two different editions, the first in Lyon and the second almost 70 years later in Florence. The drawings published in Lyon are found to be slightly different from those published in Florence, which produces a discrepancy in the position of spots of a few degrees, while sunspot group areas may differ by a factor of two. We reveal that the orientation of the drawings in the book is not always the same as might be seen in the telescope. We conjecture that the time of Gassendi’s observations covers the beginning of a new Schwabe cycle in the southern hemisphere. The differential rotation rate in the 1630s is also assessed and discussed.
KeywordsSunspots Solar cycle, observations Sunspots, velocity
We use data from the Royal Greenwich Observatory, United States Air Force, National Aeronautics and Space Administration (RGO/USAF/NOAA: solarscience.msfc.nasa.gov/greenwch.shtml ), the revised version of Greenwich Photoheliographic Results (GPR) sunspot catalogue provided by the Debrecen Heliophysical Observatory (DHO: fenyi.solarobs.unideb.hu/deb_obs_en.html ), regular solar observations at the Kislovodsk Mountain Astronomical Station GAS GAO ( en.solarstation.ru ), the database by Hoyt and Schatten (1998) provided by the National Geophysical Data Center (NOAA/NGDS: ngdc.noaa.gov/stp/SOLAR ), sunspot positions provided by Arlt et al. (2016) and Soon and Yaskell (2003), and the CalSky Project ( calsky.com ) by Arnold Barmettler, Switzerland.
We warmly thank Roger Ceragioli (a professional optician and specialist in the history of telescopes at the University of Arizona Steward Observatory Mirror Lab) and Albert Van Helden (professor of history, Rice University, The Galileo Project galileo.rice.edu ), who kindly helped us with the Latin texts.
The reported study was funded by RFBR according to the research project No. 16-02-00300-a.
Disclosure of Potential Conflicts of Interest
The authors declare that they have no conflicts of interest.
- Gassendi, P.: 1658, Diniensis ecclesiae praepositi ... opera omnia in sex tomos divisa. Tomus quartus, L. Anisson & Joan B. Devenet, Ludguni. Google Scholar
- Gassendi, P.: 1727, Diniensis ecclesiae praepositi ... opera omnia in sex tomos divisa. Tomus quartus, Typis Regiae Celsitudinis, Florentiae. Google Scholar
- Owens, M.J., Cliver, E., McCracken, K.G., Beer, J., Barnard, L., Lockwood, M., Rouillard, A., Passos, D., Riley, P., Usoskin, I., Wang, Y.-M.: 2016, Near-Earth heliospheric magnetic field intensity since 1750: 1. Sunspot and geomagnetic reconstructions. J. Geophys. Res. 121, 6048. DOI. ADS. CrossRefGoogle Scholar