Nuclear star cluster

A dense, massive concentration of stars at a galaxy’s center. It can coexist with a central supermassive black hole and contains stars formed across multiple episodes.

Galactic bulge: A dense, roughly spheroidal concentration of stars near the center of a galaxy. It is the larger stellar component in which many nuclear star clusters are embedded.
Dynamical friction: The loss of orbital energy by a massive object moving through a background of stars or other matter. It can draw massive star clusters inward until they contribute stars to the nucleus.
Milky Way nuclear star cluster: The dense concentration of stars surrounding the Milky Way’s central black hole, Sagittarius A*. It is the nearest nuclear star cluster and the best-resolved example.
Nuclear stellar disk: A flattened, rotating concentration of stars in a galaxy’s central region. Its disk-like shape contrasts with the more compact, approximately spheroidal cluster.
Intermediate-mass black hole: A black hole with a mass between those of stellar-mass and supermassive black holes. Some nuclear clusters may contain one, but convincing detections remain difficult.
Supermassive black hole: A black hole with a mass of hundreds of thousands to billions of Suns, commonly found at a galaxy’s center. It can occupy the same galactic nucleus as a nuclear star cluster.
Star formation: The process by which dense regions of gas collapse to form stars. Gas reaching a galactic center can produce new generations within the nuclear cluster.
Andromeda Galaxy: The nearest large spiral galaxy to the Milky Way, located about 2.5 million light-years away. Its nucleus has a distinctive double-peaked appearance associated with an eccentric stellar disk.
Nuclear bulge: A small central stellar component, often with a flattened or boxy shape, embedded within a larger galactic bulge. It is a broader central structure that can surround or overlap a nuclear star cluster.
Black hole–nuclear star cluster connection: The observed relationship between central black holes and nuclear star clusters across galaxies. Their coexistence raises questions about shared growth and possible competition for central mass.

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