photosphere Visible surface of the Sun. It is a layer of highly luminous gas c.500km (300mi) thick and with a temperature of c.6000K, falling to 4000K at its upper level. The photosphere is the source of the Sun's visible spectrum. The lower, hotter gases produce the continuous emission spectrum, while the higher, cooler gases absorb certain wavelengths. Sunspots and other visible features of the Sun are situated in the photosphere.

photosphere The thin shell of light around the Sun from which light escapes and within which the solar spectra originate.