What is protoplanetary?

Some articles on protoplanetary:

History Of Solar System Formation And Evolution Hypotheses - Formation Hypotheses - Outstanding Issues
... to test the nebular model by finding of protoplanetary discs or even planets around other stars ... Possible processes that cause the migration include orbital friction while the protoplanetary disc is still full of hydrogen and helium gas and ...
Protoplanetary Nebula - Naming
... The name protoplanetary nebula is an unfortunate choice due to the possibility of confusion with the same term being sometimes employed when discussing the unrelated concept of protoplanetary disks ... The name protoplanetary nebula is a consequence of the older term planetary nebula, which was chosen due to early astronomers looking through telescopes and finding a similarity in appearance of planetary nebula ...
Protoplanetary Disk - Formation
... Protoplanetary disks around T Tauri stars differ from the disks surrounding the primary components of close binary systems in their size and temperature ... Protoplanetary disks have radii up to 1000 AU, and only their innermost parts reach temperatures above 1000 K ... The oldest protoplanetary disk ever discovered is 25 million years old ...
Orion Nebula - Stellar Formation
... Space Telescope have yielded the major discovery of protoplanetary disks within the Orion Nebula, which have been dubbed proplyds ... This remnant cloud is the protostar's protoplanetary disk, where planets may form ... show that dust grains in these protoplanetary disks are growing, beginning on the path towards forming planetesimals ...
Protoplanetary Disk
... 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 ... Externally illuminated photo-evaporating protoplanetary disks are called proplyds ...