Figure 9-14 Active Sun in Hα This photograph shows the chromosphere and lower corona during a solar maximum, when sunspots are abundant. The image was taken through a filter that allowed only light from Hα emission to pass through. The hot, upper layers of the Sun’s atmosphere are strong emitters of Hα photons. (See Section 3-17 for details of the Balmer series, Hα−H∞.) A few large sunspots are evident. Most notable are features that do not appear at the solar minimum, such as the snakelike features shown here called filaments, bright areas called plages, and prominences (filaments seen edge-on) observed at the solar limb.