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.
Read more about Protoplanetary Disk: Formation, Relation To Abiogenesis
Famous quotes containing the word disk:
“Unloved, that beech will gather brown,
This maple burn itself away;
Unloved, the sun-flower, shining fair,
Ray round with flames her disk of seed,
And many a rose-carnation feed
With summer spice the humming air;”
—Alfred Tennyson (1809–1892)