What does nebula mean?
In astronomy, a nebula is a diffuse cloud or mass of interstellar gas and dust. Such regions may emit light, reflect the light of nearby stars, or absorb light and appear dark. Nebulae are important because they contain the raw material from which stars and planetary systems form; embedded stars can also illuminate the surrounding gas, producing vivid colors in astronomical images. The term was once used more broadly for any indistinct, luminous object in the sky, including the Andromeda Galaxy, before modern astronomy established that many such objects were separate galaxies. Today, the word normally has a precise astronomical meaning, although it can occasionally be used figuratively for a diffuse, confusing mass. A planetary nebula is a particular kind of nebula formed from the material shed by a dying star, and it should not be confused with a nebula in which stars are being born. The word is consequently both a practical term for astronomers and an evocative image of cosmic clouds, glowing gas, and stellar beginnings.
nounA diffuse cloud or mass of interstellar gas and dust, which may emit, absorb, or reflect light.
- A diffuse cloud or mass of gas and dust in interstellar space, which may be luminous, dark, or partly obscured.
- A formerly broad astronomical term for a diffuse celestial object, especially a spiral galaxy seen in the sky as a luminous patch.
"The telescope revealed a colorful nebula glowing in the darkness."
"A nebula in the constellation Orion contains vast quantities of gas and newly forming stars."
"Early observers called the Andromeda Galaxy a nebula before its nature as a separate galaxy was established."
The standard plural is nebulae; the form nebula is not normally used as a plural in modern English.
"Several nebulae appear as colorful patches in long-exposure photographs."
Some nebulae are stellar nurseries, while planetary nebulae are the glowing leftovers of dying stars.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does nebula come from?
The word comes through Latin from nebula, meaning a mist or cloud. Latin nebula was related to Greek nephos, meaning cloud, which survives in scientific words such as nephology and nephoscope. English adopted the word in the early modern period, and its astronomical meaning became established as telescopic observations revealed luminous and dark clouds in the heavens.
Related word forms
How nebula is actually used
In astronomy, the term is standard and usually refers to interstellar gas or dust. The historical sense is now uncommon, while modern senses distinguish nebulae from stars, planets, and galaxies.