Knowra Stellar association Stellar association A loose grouping of young stars formed from the same star-forming region. Its members are not gravitationally bound and gradually disperse into the Galaxy.
Star formation : The process by which dense regions of gas and dust collapse to form stars. Associations preserve the nearby stellar products of a shared episode of star formation.
Molecular cloud dispersal : The removal or breakup of gas from a molecular cloud by stellar feedback and other processes. Removing the birth cloud weakens the collective gravity that could otherwise bind its new stars.
Open cluster : A relatively young, compact group of stars held together by mutual gravity. Unlike an association, an open cluster is gravitationally bound, at least initially.
Scorpius–Centaurus association : The nearest major OB association, composed of several young stellar subgroups in the Scorpius–Centaurus region. Its subgroups provide a nearby example of a large, structured OB association.
Molecular cloud : A cold, dense interstellar cloud composed mainly of molecular hydrogen, where stars commonly form. The stars in an association typically emerge from the same molecular cloud.
Stellar feedback : The return of energy and matter from stars to their surroundings through radiation, winds, and explosions. Feedback can expel gas and leave a young stellar grouping gravitationally unbound.
Globular cluster : A dense, roughly spherical system of old stars bound by gravity and orbiting a galaxy. Its compact, strongly bound structure contrasts with an association's youth and looseness.
Orion OB1 association : A complex of young stellar subgroups in the Orion region, including many massive stars. Its subgroups illustrate how associations can contain populations of different ages.
Stellar kinematics : The study of stars' motions through space, including their velocities and orbital paths. Related motions help identify association members after the group begins to spread.
Virial equilibrium : A dynamical state in which a system's kinetic and gravitational potential energies satisfy the virial theorem. Associations are expanding or dispersing rather than settled into virial equilibrium.
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