Search results
Results from the WOW.Com Content Network
A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may not be considered an accretion disk ; while the two are similar, an accretion disk is hotter and spins much faster.
A gas flow then develops from the companion star to the primary. Angular momentum conservation prevents a straight flow from one star to the other and an accretion disk forms instead. Accretion disks surrounding T Tauri stars or Herbig stars are called protoplanetary disks because they are thought to be the progenitors of planetary systems.
ALMA image of HL Tauri, a protoplanetary disk. In astrophysics, accretion is the accumulation of particles into a massive object by gravitationally attracting more matter, typically gaseous matter, into an accretion disk. [1] [2] Most astronomical objects, such as galaxies, stars, and planets, are formed by accretion processes.
In astronomy, a disk wind is a particle outflow observed around accretion disks, mainly near protoplanetary disks [1] [2] and active galactic nulei (AGN). [3] [4] The disk wind is made up of a gaseous and a dusty component. [1] Especially in edge-on protoplanetary disks this disk wind can be directly imaged. [5] [6]
Protoplanetary disks and debris disks can be imaged with different methods. If the disk is seen edge-on, the disk can sometimes block the light of the star and the disk can be directly observed without a coronagraph or other advanced techniques (e.g. Gomez's Hamburger or Flying Saucer Nebula [27]).
The protoplanetary disk is sometimes referred to as an accretion disk, because while the young T Tauri-like protostar is still contracting, gaseous material may still be falling onto it, accreting on its surface from the disk's inner edge. [40] In an accretion disk, there is a net flux of mass from larger radii toward smaller radii. [23]
When this accretion phase is nearly complete, the resulting object is known as a protostar. [4] N11, part of a complex network of gas clouds and star clusters within our neighbouring galaxy, the Large Magellanic Cloud. Accretion of material onto the protostar continues partially from the newly formed circumstellar disc.
Debris disks detected in HST archival images of young stars, HD 141943 and HD 191089, using improved imaging processes (24 April 2014). [1] 486958 Arrokoth, the first pristine planetesimal visited by a spacecraft. Planetesimals (/ ˌ p l æ n ɪ ˈ t ɛ s ɪ m əl z /) are solid objects thought to exist in protoplanetary disks and debris disks.