- Latin for Cloud. The term was originally applied to any non-point source of light from outside the solar system, but is now no longer used to describe galaxies. A wide range of types of nebulae are recognised, including dark and bright types, some dominated by gas and others in which dust is a major component. Dark nebulae are seen as dark outlines against bright objects – the Coalsack being a prime example. Among bright nebulae are reflection nebulae which shine by light reflected from other objects, emission nebulae which glow, usually from emissions from hot, young stars, and planetary nebulae, which are expanding gas bubbles resulting from nova explosions. The solar nebula is the term for the mass from which the Sun and the rest of the solar system have condensed. The types of nebula merge into each other and a given nebula can have parts which absorb radiation, and others which reflect or retransmit it.
- noun a slightly cloudy spot on the cornea
- noun a spray of medicinal solution, applied to the nose or throat using a nebuliser
Origin & History of “nebula”
As its form suggests, nebula was originally a Latin word, but it goes back to a prehistoric Indo-European base (*nebh- ‘cloud’) which produced a wide range of other descendants, including German nebel ‘cloud’, Greek néphos ‘cloud’, and Latvian debess ‘sky’. It also got into Old English, as nifol ‘dark’. The Latin word was originally used in English for a sort of ‘cataract’ over the eye, and the present-day astronomical application to a ‘cloud’ of stars did not emerge until the early 18th century. The derivative nebulous (16th c.) is an earlier borrowing.