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Thin disks were independently worked out by Lynden-Bell, Pringle, and Rees. Pringle contributed in the past thirty years many key results to accretion disk theory, and wrote the classic 1981 review that for many years was the main source of information about accretion disks, and is still very useful today.
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.
The disk of a Class 0 protostar is thought to be massive and hot. It is an accretion disk, which feeds the central protostar. [39] [40] The temperature can easily exceed 400 K inside 5 AU and 1,000 K inside 1 AU. [51] The heating of the disk is primarily caused by the viscous dissipation of turbulence in it and by the infall of the gas from the ...
The torque caused a magnetic coupling and acted to transfer angular momentum from the Sun to the disk. The magnetic field strength would have to have been 1 gauss. The existence of torque depended on magnetic lines of force being frozen into the disk, a consequence of a well-known magnetohydrodynamic (MHD) theorem on frozen-in lines of force ...
This theory explains the extraction of energy from magnetic fields around an accretion disk, which are dragged and twisted by the spin of the black hole. Relativistic material is then feasibly launched by the tightening of the field lines. Penrose mechanism. [16]
Accretion of gas on both planets also tends to reduce the supply toward the inner disk, lowering the accretion rate toward the Sun. This process works to deplete somewhat the disk interior to Jupiter's orbit, weakening the torques on Jupiter arising from inner Lindblad resonances and potentially ending the planets' outward migration. [11]
The most accepted theory for the energy source of active galactic nuclei is the presence of an accretion disk around a supermassive black hole.
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.