Our Astronomical Column


    A Large Sunspot.—A large group of sunspots recently visible is the largest that has appeared for over a year. The group when near the sun's east limb on Feb. 14 was quite small, but between Feb. 17 and 19 it developed rapidly, and by Feb. 21 had become a conspicuous stream of spots easily visible to the naked eye. The central meridian passage of the group occurred on Feb. 20-8; its latitude was 6°, and its area on Feb. 17, 19, and 21 was respectively 150, 900, and 1700 millionths of the sun's hemisphere. On Feb. 19, spectroscopic observations made at 15h showed a mass of hydrogen to be descending into the following member of the group with the velocity of about 30 km./sec. On succeeding days the group was not unusually active, so far as rather limited observations showed. It may be remarked that sunspots during 1930 were both appreciably less in number and smaller than in 1929. The sunspot minimum may be expected in two or three years' time.

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    Our Astronomical Column. Nature 127, 321 (1931). https://doi.org/10.1038/127321a0

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