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Self-gravitation is the gravitational force of an object on itself, i.e., on other portions of itself. It keeps stars and planets intact, and presumably galaxies, galaxy clusters, and many clouds; these are termed self-gravitating bodies. Small solid objects, such as a chair, are basically unaffected by self-gravitation: at such a small scale, the gravity of chair material on portions of the chair is so small as to be immeasurable and certainly beyond practical use; such objects are held together by chemical bonds. A meteoroid is presumably not held together by self-gravitation but for such objects, considering larger sizes and masses, there comes a point where self-gravitation holds it together, and even loose material still remains with the object if undisturbed, i.e., it normally does not drift away.
Much physical phenomena is modeled ignoring self-gravitation, in situations where it is not significant. For some astrophysical phenomena, whether to include it in a model can be an issue. Disks are an example in which it may be necessary to figure out whether self-gravitation (e.g., whether gravitational force of some dense portion of the disk on surrounding portions) is sufficiently significant to suggest including it in a model.