The Maunder Minimum, also known as the "prolonged sunspot minimum", was a period around 1645 to 1715 during which sunspots became exceedingly rare. During the 28-year period 1672–1699 within the minimum, observations revealed fewer than 50 sunspots. This contrasts with the typical 40,000–50,000 sunspots seen in modern times over a similar timespan.
The Maunder Minimum was first noted by Gustav Spörer in publications in 1887 and 1889, work that was relayed to the Royal Astronomical Society in London, and then expanded on, by solar astronomers Edward Walter Maunder (1851–1928), and his wife Annie Russell Maunder (1868–1947), who also studied how sunspot latitudes changed with time. Two papers were published in Edward Maunder's name in 1890 and 1894, and he cited the two earlier papers written by Gustav Spörer. Because Annie Maunder had not received a university degree, restrictions at the time caused her contribution not to be publicly recognized. The term Maunder Minimum was popularised by John A. Eddy, who published a landmark paper in Science in 1976.