资料来源 : Webster's Revised Unabridged Dictionary (1913)

Planetary \Plan"et*a*ry\, a. [Cf. L. planetarius an astrologer,
   F. plan['e]taire planetary. See {Planet}.]
   1. Of or pertaining to the planets; as, planetary
      inhabitants; planetary motions; planetary year.

   2. Consisting of planets; as, a planetary system.

   3. (Astrol.) Under the dominion or influence of a planet.
      ``Skilled in the planetary hours.'' --Drayton.

   4. Caused by planets. ``A planetary plague.'' --Shak.

   5. Having the nature of a planet; erratic; revolving;
      wandering. ``Erratical and planetary life.'' --Fuller.

   {Planetary days}, the days of the week as shared among the
      planets known to the ancients, each having its day.
      --Hutton.

   {Planetary nebula}, a nebula exhibiting a uniform disk, like
      that of a planet.

资料来源 : WordNet®

planetary nebula
     n : 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