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Galaxies are gravitationally bound systems of stars, interstellar gas and dark matter, often hosting a central supermassive black hole. For questions about the structure, composition, dynamics, classification, etc. of galaxies. This includes small systems of interacting galaxies (i.e. merger, or galaxy + satellite system), but for galaxy groups and clusters use [galaxy-clusters], and for questions specific to our own Milky Way galaxy use [milky-way].

Galaxies are massive systems held together by gravitational attraction, consisting of , star systems, star clusters and the ISM (), stellar remnants, cosmic dust and an important but not yet completely understood component called . Many galaxies, perhaps all, host a central super-massive .

For questions about the structure, composition, dynamics, classification, etc. of galaxies. This includes small systems of interacting galaxies (i.e. merger, or galaxy + satellite system), but for galaxy groups and clusters use , and for questions specific to our own Milky Way galaxy use .

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