Comet Hale-Bopp Over Arizona’s Superstition Mountains, 1997. Photo by William R. Dellinges. Clearly visible are the comet’s white dust tail that shines by reflected sunlight, and the blue ion tail that shines by glowing gas.

Comet Hale-Bopp Over Arizona’s Superstition Mountains, 1997. Photo by William R. Dellinges. Clearly visible are the comet’s white dust tail that shines by reflected sunlight, and the blue ion tail that shines by glowing gas.