Photosphere but more tenuous corona. Other "surface features" on the photosphere are solar flares and sunspots. Photosphere The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/"phos, photos" meaning "light" and σφαῖρα/"sphaira" meaning "sphere", in reference to it being a spherical surface that is perceived to emit light. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately 2/3, or equivalently, a depth from which 50% of light will escape without being scattered. In other words, a photosphere is the
Spherical shell to "r" (formula_4). A Dyson sphere encloses a fictitious spherical shell around a star, as first described by author Olaf Stapledon. Spherical shell In geometry, a spherical shell is a generalization of an annulus to three dimensions. It is the region between two concentric spheres of differing radii. The volume of a spherical shell is the difference between the enclosed volume of the outer sphere and the enclosed volume of the inner sphere: where is the radius of the inner sphere and "R" is the radius of the outer sphere. An approximation for the volume of a thin spherical shell