1. Path. A spot or marking on the skin caused by exposure to the sun.
1818–20. E. Thompson, Cullen’s Nosologia (ed. 3), 333. Ephelis; Sun Spots.
1872–4. Jefferies, Toilers of Field (1892), 262. Her brown but clear cheek, free from freckles and sun-spots.
2. Astron. A spot or patch on the disk of the sun, appearing dark by contrast with the brighter general surface, and constituted by a cavity in the photosphere filled with cooler vapors.
Sun-spots occur only in a zone extending 45° on each side of the sun’s equator, often in groups, and last from a few hours to several months; their diameter varies from about 100 to about 100,000 miles; their frequency shows a marked period of about 11 years, corresponding to a periodicity of magnetic and possibly other phenomena on the earth.
1868. Lockyer, Elem. Astron., § 121. Its [sc. the magnetic needle’s] greatest oscillations occurring when there are most sun-spots.
1878. Newcomb, Pop. Astron., III. ii. 248. 1882, 1893, etc., will be years of numerous sun-spots.
1894. W. L. Dallas, in Indian Meteorol. Mem., VI. 2. The maximum rainfall agreeing approximately with the maximum sunspots.
b. attrib.
1883. Science, I. 462/1. The maximum of auroras corresponds with the minimum sun-spot period.
1884. H. F. Blanford, in Indian Meteorol. Mem. (1894), VI. 2. The epoch of sunspot maximum approximately coincides with that of minimum pressure.
1913. H. H. Turner, in Monthly Notices R. Astron. Soc., Dec., 89. The main Sun-spot swarm was in perihelion in 1816–7.
Hence Sunspottery [-ERY 2], humorous or contemptuous term for the subject or theory of sunspots, esp. of their connection with terrestrial phenomena.
1882. R. A. Proctor, in Standard, 27 Nov., 2/4. I doubt whether even a twelfth of the astronomers of our time favour ‘Sunspottery.’
