A facula // (plural: faculae //), Latin for "little torch", is literally a "bright spot". The term has several common technical uses. It is used in planetary nomenclature for naming certain surface features of planets and moons, and is also a type of surface phenomenon on the Sun's photosphere. In addition, a bright region in the projected field of a light source is sometimes referred to as a facula, and photographers often use the term to describe bright, typically circular features in photographs that correspond to light sources or bright reflections in a defocused image.
Solar faculae are bright spots in the photosphere that form in the canyons between solar granules, short-lived convection cells several thousand kilometers across that constantly form and dissipate over timescales of several minutes. Faculae are produced by concentrations of magnetic field lines. Strong concentrations of faculae appear in solar activity, with or without sunspots. The faculae and the sunspots contribute noticeably to variations in the solar constant. The chromospheric counterpart of a facular region is called a plage.
Faculae on Mercury are bright areas often surrounding irregular depressions. They are generally interpreted to be pyroclastic in nature. The faculae on Mercury are all named using words in different languages meaning snake.
Cererian faculae were initially speculated to suggest current or past outgassing on Ceres, perhaps due to volcanism or cometary activity. The brightest cluster of spots (Cereale Facula) is located in the center of an 80-kilometer (50 mi) crater called Occator. These bright features have an albedo of about 40%, four times brighter than the average of Ceres's surface. The spots appear to be mostly sodium carbonate (Na
3), implying that hydrothermal activity followed by evaporation of the water is probably what created the spots.
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- LPSC 2015: First results from Dawn at Ceres: provisional place names and possible plumes
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