Sunspot have an irregular cycle of 11 years, though intervals as short as 7 years and as long as 17 years have been recorded.
Not every cycle displays the same number or size of sunspots.
In particular, between A.D. 1645 and 1715, an era dubbed the Maunder Minimum after British astronomer E. W. Maunder, who detected it, sunspot activity was scarce.
This coincides with the middle or coldest part of a period of cooling known as the Little Ice Age.
Fluctuations in the cycle are likely to occur again, but no one really knows whether they will have any impact on Earth.
Over the last decades the Sun has had a markedly high average level of sunspot activity.
