Photospheres

Photospheres are the visible surfaces of stars, including the Sun. It is the layer of a star’s atmosphere from which most of the star’s light escapes, commonly defined as the region where the optical depth is about 2/3. In the Sun, the photosphere has a temperature near 5,500 to 6,000 kelvin and emits a blackbody-like continuum with numerous absorption lines produced by elements in the photosphere (Fraunhofer lines).

It is not a solid surface but a gaseous layer. Convection produces granulation patterns, and stronger magnetic fields give rise to cooler regions known as sunspots. The photosphere is the origin of the Sun’s visible spectrum and serves as the effective “surface” for many diagnostic techniques, including spectroscopy and Doppler measurements. Observations of the photosphere enable determinations of temperature, composition, motion, and magnetic fields.

In digital media, photosphere or photo sphere refers to a spherical panorama image, typically 360 degrees, projected onto a sphere for interactive viewing. Such photospheres are created with 360-degree cameras or by stitching multiple photos and are commonly displayed in equirectangular projection in virtual reality viewers, online tours, and mapping applications.

Because the term spans astronomy and photography, photospheres can denote either the visible surfaces of stars or digital spherical images. In astronomy, observations of the photosphere inform models of temperature, composition, and dynamics; in media, they enable immersive, navigable environments but require careful handling of projection and distortion.