Noun
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: WordNetAbsorbed ultraviolet light energises the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula. Source: Internet
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. Source: Internet
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. Source: Internet
A planetary nebula that might have a binary system at its center. Source: Internet
It covers 0.25 square degrees, making it also the largest planetary nebula as seen from Earth. Source: Internet
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. Source: Internet