---
title: "Planetary nebula"
id: "planetary-nebula"
project: "Interstellar Travel Safety Procedures Publication2"
url: "https://hedronlabs.clickhelp.co/articles/interstellar-travel-safety-procedures-publication2/planetary-nebula"
updated: 2026-10-01T08:39:32Z
---

# Planetary nebula

##  Planetary nebula
 
A planetary nebula (PN, plural PNe) is a type of [emission nebula](https://en.wikipedia.org/wiki/Emission_nebula) consisting of an expanding, glowing shell of [ionized](https://en.wikipedia.org/wiki/Ionization) gas ejected from [red giant](https://en.wikipedia.org/wiki/Red_giant) [stars](https://en.wikipedia.org/wiki/Star) late in their lives.

The term "planetary nebula" is a [misnomer](https://en.wikipedia.org/wiki/Misnomer) because they are unrelated to [planets](https://en.wikipedia.org/wiki/Planet). The term originates from the planet-like round shape of these [nebulae](https://en.wikipedia.org/wiki/Nebula) observed by astronomers through early [telescopes](https://en.wikipedia.org/wiki/History_of_the_telescope). The first usage may have occurred during the 1780s with the English astronomer [William Herschel](https://en.wikipedia.org/wiki/William_Herschel) who described these nebulae as resembling planets; however, as early as January 1779, the French astronomer [Antoine Darquier de Pellepoix](https://en.wikipedia.org/wiki/Antoine_Darquier_de_Pellepoix) described in his observations of the [Ring Nebula](https://en.wikipedia.org/wiki/Ring_Nebula), "very dim but perfectly outlined; it is as large as Jupiter and resembles a fading planet". Though the modern interpretation is different, the old term is still used.