Weather in Space

Sunspots and Solar Activity

What is the Wolf Number?

Sunspot Activity 1000 C.E. to Present

Years (c.e.) Name
1010 to 1050 Oort Minimum
1100 to 1250 Medieval Maximum
1280 to 1340 Wolf Minimum
1420 to 1530 Spörer Minimum
1645 to 1715 Maunder Minimum
1790 to 1820 Dalton Minimum
1950 to Present Modern Maximum

Swiss astronomer Johann Rudolf Wolf (1816–1893) devised a system for counting sunspots in 1848. The Wolf Number is named in his honor. Astronomers count sunspots from various observation points across the globe, then average those counts to come up with the official Wolf Number for that period.


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