Self-gravitation

thumb|A self-gravitating accretion disc in a quasi steady state Self-gravity is gravitational force exerted by a system, particularly a celestial body or system of bodies, onto itself. At a sufficient mass, this allows the system to hold itself together. The effects of self-gravity have significance in the fields of astronomy, physics, seismology, geology, and oceanography.

The strength of self-gravity differs with regard to the size of an object, and the distribution of its mass. For example, unique gravitational effects are caused by the oceans on Earth or the rings of Saturn. Donald Lynden-Bell, a British theoretical astrophysicist, constructed the equation for calculating the conditions and effects of self gravitation. The equation's main purpose is to give exact descriptions of models for rotating flattened globular clusters. It is also used in understanding how galaxies and their accretion discs interact with each other. Outside of astronomy, self-gravity is relevant to large-scale observations (on or near the scale of planets) in other scientific fields.