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Wolf’s sunspot number
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Wolf’s sunspot number

astronomy
Also known as: Wolf number, Zurich relative sunspot number, international sunspot number(Show More)
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Quick Summary

The Wolf number, also known as the sunspot number, is a system for gauging solar activity by counting sunspots and sunspot groups. This method was devised by Swiss astronomer Rudolf Wolf in 1849. Wolf confirmed Samuel Heinrich Schwabe's discovery of an approximately 11.1-year cycle in sunspot activity and correlated it with Earth's magnetism. The Wolf number is still in use today to measure solar activity.123

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3 Britannica Sources
  1. Wolf number
  2. Rudolf Wolf
  3. Sun - History of observation

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