selfluminous

Self-luminous describes something that emits light from within rather than merely reflecting ambient light. In physics, a self-luminous body generates visible radiation through internal energy sources, such as thermal energy, chemical reactions, or radioactive decay.

Natural self-luminous sources include the Sun and other stars, which produce light through nuclear fusion and transport energy outward. Some organisms also produce light biologically, a phenomenon known as bioluminescence, seen in certain marine creatures, fungi, and insects like fireflies. The light from these sources is generated by internal chemical or nuclear processes rather than by external illumination.

Artificial self-luminous sources are those that produce light without relying on reflected light. This category includes light-emitting devices that convert electrical energy into light, such as light-emitting diodes and traditional electric lamps. It also encompasses radioluminescent materials, which emit light due to radioactive decay, and phosphorescent or chemiluminescent materials that glow after being excited by an external stimulus. Such materials are used in safety signage, watches, and various special applications where a constant or persistent light source is desirable.

Self-luminous is distinct from objects that are merely illuminated by external light. Reflective surfaces, for example, rely on ambient illumination and do not emit their own light. In practice, the term is used across disciplines with slight nuance: in astronomy, it denotes bodies that radiate energy; in materials science and design, it encompasses devices and materials that generate light through internal processes.

See also: luminescence, bioluminescence, radioluminescence.