The Maunder Minimum, also known as the "prolonged sunspot minimum", was a period around 1645 to 1715 during which sunspots became exceedingly rare. During a 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. The Maunder Minimum occurred within the Little Ice Age, a long period of lower-than-average European temperatures. The reduced solar activity may have contributed to the climatic cooling, although the cooling began before the solar minimum and its primary cause is believed to be volcanic activity. Sunspot observations The Maunder Minimum occurred between 1645 and 1715 when very few sunspots were observed. That was not because of a lack of observations, as during the 17th century, Giovanni Domenico Cassini carried out a systematic program of solar observations at the Observatoire de Paris, thanks to the astronomers Jean Picard and Philippe de La Hire. Johannes Hevelius also performed observations on his own. Here is the total of sunspots recorded, by example, in the decennial years (omitting Wolf numbers): During the Maunder Minimum enough sunspots were sighted so that 11-year cycles could be determined from the count. The maxima occurred in 1676–1677, 1684, 1695, 1705 and 1718. Sunspot activity was then concentrated in the southern hemisphere of the Sun, except for the last cycle when the sunspots appeared in the northern hemisphere. According to Spörer's law, spots appear at high latitudes at the start of a cycle, subsequently moving to lower latitudes until they average about latitude 15° at solar maximum. The average then continues to drift lower to about 7° and after that, while spots of the old cycle fade, new cycle spots start