<P> The visible surface of the Sun , the photosphere , is the layer below which the Sun becomes opaque to visible light . Above the photosphere visible sunlight is free to propagate into space , and almost all of its energy escapes the Sun entirely . The change in opacity is due to the decreasing amount of H ions , which absorb visible light easily . Conversely , the visible light we see is produced as electrons react with hydrogen atoms to produce H ions . The photosphere is tens to hundreds of kilometers thick , and is slightly less opaque than air on Earth . Because the upper part of the photosphere is cooler than the lower part , an image of the Sun appears brighter in the center than on the edge or limb of the solar disk , in a phenomenon known as limb darkening . The spectrum of sunlight has approximately the spectrum of a black - body radiating at about 6,000 K , interspersed with atomic absorption lines from the tenuous layers above the photosphere . The photosphere has a particle density of ~ 10 m ( about 0.37 % of the particle number per volume of Earth 's atmosphere at sea level ) . The photosphere is not fully ionized -- the extent of ionization is about 3 % , leaving almost all of the hydrogen in atomic form . </P>
<P> The visible surface of the Sun , the photosphere , is the layer below which the Sun becomes opaque to visible light . Above the photosphere visible sunlight is free to propagate into space , and almost all of its energy escapes the Sun entirely . The change in opacity is due to the decreasing amount of H ions , which absorb visible light easily . Conversely , the visible light we see is produced as electrons react with hydrogen atoms to produce H ions . The photosphere is tens to hundreds of kilometers thick , and is slightly less opaque than air on Earth . Because the upper part of the photosphere is cooler than the lower part , an image of the Sun appears brighter in the center than on the edge or limb of the solar disk , in a phenomenon known as limb darkening . The spectrum of sunlight has approximately the spectrum of a black - body radiating at about 6,000 K , interspersed with atomic absorption lines from the tenuous layers above the photosphere . The photosphere has a particle density of ~ 10 m ( about 0.37 % of the particle number per volume of Earth 's atmosphere at sea level ) . The photosphere is not fully ionized -- the extent of ionization is about 3 % , leaving almost all of the hydrogen in atomic form . </P>
what is the name of the surface of the sun
what is the name of the surface of the sun
photosphere
photosphere