Astrophysics & Particle Physics-APPC 2026

Accretion disks are gas, plasma, or dust rotating structures that revolve about large objects like black holes, neutron stars, white dwarfs, or young protostars. They develop as material loses angular momentum and spirals toward the center, dissipating gravitational potential energy as heat, radiation, and occasionally intense jets.Accretion disks about black holes and neutron stars are a central source of high-energy radiation, such as X-rays and gamma rays, in X-ray binaries and active galactic nuclei (AGNs).

The accretion process is governed by viscosity, angular momentum transport, and magnetohydrodynamic turbulence that regulate mass inflow and energy dissipation rates.Accretion disks also have important roles in stellar evolution and planet formation. Protostellar accretion disks supply the material to make planets and control the central star's growth in young stellar systems. Infrared, optical, and radio observations show disk structure, gaps, rings, and temperature gradients, illuminating disk dynamics and planet formation mechanisms.Near compact objects, the disk interior can become very hot, emitting thermal emission and non-thermal radiation detectable over the electromagnetic spectrum. Accretion disks may accelerate relativistic jets through interactions with magnetic fields to play a role in the creation of astrophysical outflows observed in AGNs, microquasars, and gamma-ray bursts.Examination of accretion disks gives a clue into the fundamental physics under extreme conditions such as strong gravity, relativistic dynamics, and high-energy particle acceleration.

X-ray telescope, radio interferometer, and space-based observatory observations assist in measuring disk luminosity, spectra, and variability and uncover the intricate interaction between matter and compact objects.Accretion disks are at the core of understanding compact object accretion, high-energy astrophysical processes, jet formation, and the formation of planets and thus are central topics in both observational and theoretical astrophysics.