A Protoplanetary Disk (or Preplanetary Disk) is a Circumstellar Disk, consisting of Dust and gas orbiting a young star or Protostar such as a T-Tauri Star. Radii can be as much as 1000 AU. Such disks are thought to provide the material for Planet Formation. The disks often develop a flared torus shape due to a combination of heat and Radiation Pressure from the central star. They can last several million years, evolving through Accretion, outflows, Photoevaporation, and/or condensation into larger bodies, small to large (Planetesimals or planets).
The term Proplyd is used for observed protoplanetary disks, visible for being illuminated, typically by the star's Ultraviolet radiation, resulting in Photodissociation ionization and Velocity Dispersion.
Carbon Monoxide (CO)
Core Accretion Model
Gravitational Instability Model
Infrared Space Observatory (ISO)
Meter Size Barrier
Rossby Wave Instability (RWI)
Stellar Age Determination
T-Tauri Star (TTS)