Tidal stripping

Tidal stripping is the removal of material from an astronomical object when another object's gravity overcomes its ability to hold that material. It can reshape galaxies, star clusters, and smaller bodies.

Tidal force: A differential gravitational force caused by variation in a gravitational field across an extended object. The difference in gravitational pull across an object supplies the force that strips its material.
Sagittarius Dwarf Spheroidal Galaxy: A dwarf spheroidal galaxy currently being disrupted by the Milky Way. Its stellar streams trace stars removed during repeated passages around the Milky Way.
Stellar halo: The diffuse, roughly spherical population of stars surrounding a galaxy's central disk or bulge. Accreted and stripped satellite stars help build the Milky Way's stellar halo.
Ram-pressure stripping: The removal of gas from a galaxy as it moves through the hot gas of a galaxy cluster. It strips gas through hydrodynamic pressure rather than differential gravity.
Roche limit: The distance within which a body's tidal forces can overcome the self-gravity holding another body together. Crossing this distance can make a satellite unable to retain its material.
Stellar stream: An elongated structure of stars stripped from a star cluster or dwarf galaxy by tidal forces. Streams are the extended debris left behind when a bound system loses stars.
Galactic archaeology: The reconstruction of a galaxy's formation history from the ages, chemistry, and motions of its stars. The chemical and orbital patterns of stripped stars preserve evidence of past accretion.
Galaxy harassment: The cumulative dynamical disturbance of a galaxy through repeated high-speed encounters with other galaxies. Repeated encounters can reshape galaxies without the stripping being solely a steady tidal process.
Hill sphere: The region around an astronomical body where its gravity can retain satellites against a larger body's perturbations. Material beyond this gravitational domain is especially vulnerable to removal.
Globular cluster: A dense, roughly spherical collection of old stars bound by mutual gravity. Tidal stripping can remove its outer stars and contribute to the Milky Way's stellar halo.

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