planetary nebula
Noun
Meaning
a nebula that was once thought to be a star with its planets but is now thought to be a very hot star surrounded by an expanding envelope of ionized gases that emit a fluorescent glow because of intense radiation from the star
Source: WordNetSynonyms
Hypernyms
Examples
Absorbed ultraviolet light energises the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula.
A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from old red giant stars late in their lives.
Artist's depiction of the life cycle of a Sun-like star, starting as a main-sequence star at lower left then expanding through the subgiant and giant phases, until its outer envelope is expelled to form a planetary nebula at upper right.
A planetary nebula that might have a binary system at its center.
It covers 0.25 square degrees, making it also the largest planetary nebula as seen from Earth.
For one reason, the planetary nebula phase for more massive stars is on the order of thousands of years, which is a blink of the eye in cosmic terms.