Wikipedia
Self-gravity is the gravitational force exerted on a body, or a group of bodies, by the body(ies) that allows it/them to be held together. Self-gravity (self-gravitation) has important effects in the fields of astronomy, physics, seismology, geology, and oceanography. Self-gravity has important impacts in regard to the physical behavior on large scale (planet size or larger) objects, such as the oceans on Earth or the rings of Saturn. The equation to calculate the effects of self-gravitation were made exact by Lynden-Bell for the purpose of giving an exact description of models for rotating flattened globular clusters, which was a crucial step in understanding how clusters of stars interact with each other. Self-gravity deals with large-scale observations in fields outside of astronomy as well. Self-gravity does not typically appear as the central focus of scientific research, but understanding it and being able to include its effects mathematically increases the accuracy of models and understanding large-scale systems.