Definition of planetary nebula in US English:

planetary nebula


  • A ring-shaped nebula formed by an expanding shell of gas around an aging star.

    • ‘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.’