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 stars, star systems, star clusters and the ISM (interstellar-matter), stellar remnants, cosmic dust and an important but not yet completely understood component called dark-matter. Many galaxies, perhaps all, host a central super-massive 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.
