Photospheres

Part of speech: noun

Definitions

1. The luminous outer shell of a star, particularly the visible surface from which light is emitted
2. A layer of gas surrounding a celestial object, mainly associated with the Sun, that emits and absorbs radiation
3. The region from which electromagnetic radiation is detectable, characterized by thermal and optical properties that define a star's appearance

Etymology: "Photospheres" is simply the plural of "photosphere", so its history is that of the single word. The term is built from two Greek-derived elements: "photo-", from Greek "phōs" meaning light, and "-sphere", from Greek "sphaira" meaning ball or globe. Joined together, they describe a luminous globe, which is exactly what a star's visible outer layer looks like from a distance. The "-sphere" element is the older and more widely recognised of the two, appearing in English words such as "atmosphere" and "hemisphere", while "photo-" has become familiar through words like "photograph". Combining these in astronomy gave astronomers a neat label for the glowing outer shell of a star, the region that gives the star its visible surface.

Synonyms: stellar surfaces, star surfaces, photosurfaces, luminescent spheres, radiant spheres