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sunspot number

noun, Astronomy

Wolf number

[woo lf; French vawlf] /wʊlf; French vɔlf/
noun, Astronomy
a number indicating the degree of sunspot activity on the sun as a factor of observer idiosyncrasies, the number of sunspot groups, and the number of individual sunspots.
Also called relative sunspot number, sunspot number.
Origin of Wolf number
1975-80; after Rudolf Wolf (1816-93), Swiss astronomer Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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