SPICULE

in astronomy, rising jet of comparatively cool, dense gas extending through the chromosphere, or lower atmosphere, of the Sun. The corona, or outer atmosphere, is above the spicules and seems to be formed from them. About 100,000 spicules are active in the Sun at any given time. Each rises from the lower chromosphere at about 20 km (12 miles) per second to a height of several thousand kilometres and then within a few minutes disperses or collapses. Spicules appear to be independent of sunspots and other local events in the underlying photosphere. See chromosphere.