Extra radiation at certain specific wavelengths in a spectrum, compared with neighboring wavelengths (colors).

1. A nebula which, as a result of ionized gas within it, shines by its own light.
2. A gas cloud that receives energy from a hot star, allowing it to give off radiation in emission lines; such as, those of hydrogen.

The characteristic reddish radiation of many emission nebulae is mostly from the hydrogen-alpha line.

The spectrum formed by the emission of electromagnetic radiation by a source; such as, a star.

Electromagnetic radiation emitted or absorbed at discrete frequencies or wavelengths.

The type of electromagnetic radiation emitted when electrons and atoms forming part of a hot gas interact by collisions; the resulting radiation is continuous, as opposed to discrete, line emission.