Kepler's Old Sketches Help Solve Sun Mystery

In a remarkable intersection of history and modern science, sketches of sunspots made by German astronomer Johannes Kepler in 1607 are aiding researchers in unraveling solar activity patterns from the 17th century. This period is critical for understanding the sun's 11-year solar cycle, which fluctuates between periods of heightened and diminished activity. The significance of Kepler's drawings, previously overlooked for quantitative analysis, has been re-evaluated, revealing insights into the solar cycle phase during his observations. Researchers, including Hayakawa, have focused on reconstructing the heliographic coordinates to pinpoint the location of sunspots observed by Kepler. This effort is complemented by studies of cosmic rays and their impact on Earth's atmospheric chemistry, particularly the carbon isotopes found in tree rings and ice cores. These isotopes provide a historical context for sunspot observations, extending knowledge of solar activity prior to systematic records. The findings indicate that the sunspot group Kepler documented corresponds to the tail-end of Solar Cycle minus 14, rather than the onset of Solar Cycle minus 13. This challenges previous assumptions about the duration of these cycles, suggesting that Solar Cycle minus 13 had a standard 11-year length, aligning with Spörer’s law regarding solar cycle transitions. As scientists continue to explore the implications of Kepler's work, they aim to identify further precursors to the Maunder Minimum, a period marked by significantly reduced solar activity. This research underscores the enduring relevance of historical scientific observations in enhancing contemporary understanding of solar dynamics.