Circumstellar disc

A flattened distribution of gas, dust, or both that orbits a star. It can form from material expelled by a star or remain from the star’s formation.

Angular momentum: A measure of rotational motion, determined by an object's mass distribution and velocity. Conservation of angular momentum helps collapsing stellar material settle into a rotating disc.
Protostar: A young stellar object still gaining mass from its surroundings before sustained hydrogen fusion begins. A protostar commonly forms at the center of a collapsing cloud and its surrounding disc.
Planet formation: The processes by which planets assemble from dust, pebbles, planetesimals, and gas around stars. Protoplanetary discs are the environments in which planets assemble.
Accretion disc: A rotating structure of matter that spirals inward toward a central object while releasing gravitational energy. This broader class includes circumstellar discs as well as discs around compact objects.
Keplerian rotation: Orbital motion in which speed decreases with distance from a central mass according to Kepler's laws. Most circumstellar discs orbit at speeds set mainly by the star's gravity.
Interstellar medium: The gas and dust occupying the space between stars in a galaxy. Circumstellar discs inherit material from the interstellar clouds that collapse to form stars.
Herbig–Haro object: A bright nebula formed where jets from a young star collide with surrounding gas. Jets associated with accreting young stars trace processes linked to their discs.
Circumplanetary disc: A disc of gas and dust orbiting a planet, often associated with the formation of moons. Its central object is a planet rather than a star.
Protoplanetary disc: A gas-and-dust disc around a young star from which planets can form. This common circumstellar-disc subtype supplies the raw material for planetary systems.
Hydrostatic equilibrium: A balance in which pressure gradients counteract gravity in a fluid at rest or in steady structure. Vertical pressure support helps determine a disc's thickness around its orbital plane.

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