Knowra Bondi accretion Bondi accretion Bondi accretion is the steady, spherically symmetric inflow of gas from a stationary medium onto a gravitating object. Its classical model relates the accretion rate to the object's mass and the gas's density and sound speed.
Bondi radius : The characteristic radius where a gravitating object's escape speed equals the ambient gas sound speed. It marks the scale inside which gravity can overcome the gas's pressure support.
Euler equations : The equations governing motion and conservation of mass, momentum, and energy in an ideal fluid. Bondi's steady flow follows from applying these fluid equations under spherical symmetry.
Hoyle–Lyttleton accretion : A model of gravitational capture from a uniform gas flowing past a moving object. It replaces Bondi's stationary ambient medium with a relative bulk flow.
Black hole : A region of spacetime whose gravity prevents anything, including light, from escaping beyond its event horizon. A black hole can capture ambient gas, though relativistic effects limit the classical model near its horizon.
Bondi accretion rate : The mass per unit time predicted to flow onto an object in the classical Bondi model. The model's central result depends on mass, ambient density, sound speed, and the equation of state.
Continuity equation : A conservation law stating that changes in mass density balance mass flowing into or out of a region. It makes the mass accretion rate constant with radius in a steady spherical flow.
Bondi–Hoyle–Lyttleton accretion : A model of gas accretion onto an object moving relative to a uniform medium. It extends the Bondi framework to include motion through the surrounding gas.
Neutron star : A compact stellar remnant composed predominantly of densely packed neutrons. Its gravity can capture surrounding gas, while its surface and magnetic field add physics absent from the basic model.
Bondi solution : The steady radial flow solution for gas accreting spherically from a uniform medium onto a point mass. Its velocity and density profiles describe the flow from the distant medium toward the accretor.
Spherical symmetry : A condition in which a system is unchanged by rotations about a central point. It reduces the gas motion to a radial problem, excluding disks and directional structure.
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