The photosphere, which is the atmosphere's lowest and coolest layer, is normally its only visible part.Light escaping from the surface of the star stems from this region and passes through the higher layers. The Sun's photosphere has a temperature in the 5,770 K to 5,780 K range.Starspots, cool regions of disrupted magnetic field lie on the photosphere.
Above the photosphere lies the chromosphere. This part of the atmosphere first cools down and then starts to heat up to about 10 times the temperature of the photosphere.
Above the chromosphere lies the transition region, where the temperature increases rapidly on a distance of only around 100 km.
During a total solar eclipse, the photosphere of the Sun is obscured, revealing its atmosphere's other layers. Observed during eclipse, the sun's chromosphere appears (briefly) as a thin pinkish arc, and its corona is seen as a tufted halo. The same phenomenon in eclipsing binaries can make the chromosphere of giant stars visible.
^ abLang, K.R. (September 2006). "5.1 MAGNETIC FIELDS IN THE VISIBLE PHOTOSPHERE". Sun, earth, and sky (2nd ed.). Springer. p. 81. ISBN978-0-387-30456-4. "this opaque layer is the photosphere, the level of the Sun from which we get our light and heat"
^Mariska, J.T. The solar transition region. p. 60. ISBN978-0-521-38261-8. "100 km suggested by average models"
^Lewis, J.S. (2004-02-23). Physics and chemistry of the solar system (second ed.). Elsevier Academic Press. p. 87. ISBN978-0-12-446744-6. "The dominant color is influenced by the Balmer radiation of atomic hydrogen"|accessdate= requires |url= (help)