Kepler's sketches clarify 17th-century sunspot activity decline

A study by Japanese and Belgian astronomers analyzed 17th-century sunspot sketches by Johannes Kepler, shedding light on the Maunder Minimum (1645-1715), a period with only 59 recorded sunspots compared to 40,000-50,000 in modern cycles. This research, published in The Astrophysical Journal Letters, aims to clarify the transition to this unique solar cycle, which has been debated due to conflicting tree ring reconstructions.