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| A Baby Star surrounded by Protoplanetary Disc |
A protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may be considered an accretion disc
because gaseous material may be falling from the inner edge of the disk
onto the surface of the star, but this process should not be confused
with the accretion process thought to build up the planets themselves.
Externally illuminated photo-evaporating protoplanetary disks are called
proplyds.