A ring-shaped nebula formed by an expanding shell of gas round an ageing star.
〔天文〕行星状星云
Example sentencesExamples
The Boomerang Nebula is a young planetary nebula and the coldest object found in the Universe so far.
To obtain direct clue of the presence of magnetic fields in planetary nebulae, astronomers decided to focus on the central stars, where the magnetic fields should have survived.
Until recently, it was thought that shells around planetary nebulae were a rare phenomenon.
Astronomers call such an object a planetary nebula, because its round shape resembles that of a planet when viewed with a small telescope.
One way that astronomers classify planetary nebulae is by the number of axes that they contain.
Definition of planetary nebula in US English:
planetary nebula
noun
Astronomy
A ring-shaped nebula formed by an expanding shell of gas around an aging star.
〔天文〕行星状星云
Example sentencesExamples
Until recently, it was thought that shells around planetary nebulae were a rare phenomenon.
The Boomerang Nebula is a young planetary nebula and the coldest object found in the Universe so far.
To obtain direct clue of the presence of magnetic fields in planetary nebulae, astronomers decided to focus on the central stars, where the magnetic fields should have survived.
One way that astronomers classify planetary nebulae is by the number of axes that they contain.
Astronomers call such an object a planetary nebula, because its round shape resembles that of a planet when viewed with a small telescope.