Fig. 22.—Quiet prominences of smoke-column type
Fig. 23.—Quiet prominences, shape
of a tree. The white spot indicates
the size of the earth
Fig. 24.—Diagram illustrating the differences in the spectra of sun-spots and of the photosphere. Some lines in the spot spectrum are stronger, others fainter, than in the photosphere spectrum. In the central portion, two reversals; to the right, two bands. After Mitchell
Fig. 25.—Spectrum of a sun-spot, the central band between the two portions of the photosphere spectrum. The spot spectrum is bordered with the half-shadows of the edge of the spot. After Mitchell
The quiet prominences consist almost exclusively of hydrogen and helium; sometimes they contain also traces of metallic gases. They resemble clouds floating quietly in the solar atmosphere, or masses of smoke coming from a chimney. They may appear anywhere on the sun, and their stability is so great that they have sometimes been watched during a complete solar rotation (for about forty days); this is possible only when they occur in the neighborhood of the poles, where they always remain visible outside the sun’s limb. Figs. 22 and 23 show several such prominences according to Young.
