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Concept
Self-gravitation
Summary
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.
Self-gravity must be taken into account by astronomers because the bodies being dealt with are large enough to have gravitational effects on each other and within themselves. Self-gravity affects bodies passing each other in space, within the sphere defined by their Roche limit. In this way, relatively small bodies can be torn apart, though typically the effects of self-gravitation keep the smaller body intact because the smaller body becomes elongated. This has been observed on Saturn because the rings are a function of inter-particle self-gravity. Additionally, in most astronomical circumstances the transit through a Roche limit is temporary, so the force of self-gravitation can restore the body's composition after the fact. Self-gravity is also necessary to understand quasi-stellar object discs, accretion disc formation, and stabilizing these discs around quasi-stellar objects.
Self-gravitational forces are also significant in the formation of planetesimals and indirectly the formation of planets, which is critical to understanding how planets and planetary systems form and develop over time.
Official source
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