The photosphere (coming from "photo" the Greek word for light) sits between the chromosphere and the convection level within the Suns structure. In the anatomy of the Sun it is a very thin layer measuring between 100 and 500 km thick (from a total diameter of around 700,000km). It is often considered to be the "surface" of the Sun (a very awkward thing to define considering the sun is a flaming ball of gas and isn't that dense in any of its layers), and as reflects this most measurements of the Suns physical attributes (such as diameter and volume) are taken with the photosphere as the boundary. It is also thought to be the densest region within the Suns structure, but even then it is only 0.1% of the density of air on Earth at sea level

Most of the solar energy we receive from the Sun is the visible (white) light emitted from the photosphere. The photosphere is one of the coolest regions of the Sun (between 4300K and 6000 K), so very little hydrogen gas is ionized (exists in a plasma state). The photosphere is the densest part of the solar stucture, but is still insignificant compared to Earth's atmosphere (0.01% of the density of air at sea level).

Many of the photospheres characteristics can be seen quite easily using a basic telescope with a the correct filter attatched to reduce the Suns energy to a non-damaging level(MAKE SURE YOU HAVE EXPERT SUPERVISION BEFORE ATTEMPTING THIS AS STARING DIRECTLY AT THE SUN CAN CAUSE BLINDNESS). These features include the bright faculae, and supergranules (these are large convection cells around 1000km across) large scale flows, patterns of waves and oscillations and the dark sunspots occuring at the site of strong magnetic fields (Apparently it's also possible to measure the flow of material within the photosphere using the Doppler effect)

Information taken from: photosphere.html

Pho"to*sphere (?), n. [Photo- + sphere.]

A sphere of light; esp., the luminous envelope of the sun.


© Webster 1913.

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