Knowra Globular cluster Globular cluster A dense, roughly spherical collection of stars bound by gravity, typically orbiting in a galaxy’s halo. Its stars generally formed early in the galaxy’s history and share a compact, gravitationally bound system.
Star : A luminous sphere of plasma held together by gravity and powered by nuclear fusion. Stars are the members whose combined light and motion reveal a cluster.
Two-body relaxation : The gradual change in stellar orbits caused by repeated weak gravitational encounters between pairs of stars. It redistributes energy and drives stars outward from dense cluster centers.
Galaxy formation and evolution : The processes by which galaxies form and change through the growth of stars, gas, and dark matter. Globular clusters trace early episodes in their host galaxies’ assembly.
Messier 13 : A bright globular cluster in the constellation Hercules, about 22,000 light-years from Earth. Its rich star field makes it a classic example of a dense cluster.
Gravitational binding energy : The energy required to disperse a system of masses against their mutual gravitational attraction. It quantifies the cluster’s resistance to disruption.
Core collapse : The contraction of a star cluster’s center as energy transfer causes its central density to rise. Some globular clusters develop exceptionally dense cores through this process.
Galactic halo : The extended region surrounding a galaxy’s visible disk, containing stars, gas, and dark matter. Many globular clusters orbit far beyond their galaxy’s bright disk.
47 Tucanae : A massive, bright globular cluster in the southern constellation Tucana. Its well-studied stellar populations and compact core illustrate cluster structure.
Stellar population : A group of stars characterized by shared properties such as age, chemical composition, or location. Cluster stars often share age and composition, making their population unusually coherent.
Mass segregation : The tendency for more massive stars in a cluster to become concentrated toward its center. Relaxation sorts stars by mass, changing the cluster’s radial structure.
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