Astrophysics (index)

Globular Cluster

(GC)
(spherical group of stars orbiting a galaxy)

A Globular Cluster (GC) is a group of stars, typically in the shape of a sphere, that is bound to a Galaxy and orbits its center. They may be found above or below the Galactic Plane, but within the galaxy's presumed dark-matter halo.

They are generally Population II stars, i.e., less Metal and older than the Sun.

Globular clusters and Open Clusters are generally thought to be stars formed over a short period of time, making the stars approximately the same age (Coeval). However, clusters have shown a very slight division in the plotting of the main sequence on globular cluster H-R Diagrams (HRD), and the observation of spectral signs of Aluminum and Sodium suggest a second generation of stars as these are elements likely to be synthesized by short-lived first-generation stars (O-Type Star (O) and A-Type Star (A)) in their giant phases.

Current aging methods (e.g., using the Turn-off Point (TO)) of Milky Way-globular clusters show them to be quite old, some on the order of 13 billion years, with ~10 billion years common. Examples of younger globular clusters can be found in the Magellanic Clouds.


(stars,object type)
http://en.wikipedia.org/wiki/Globular_cluster

Referenced by:
Baade's Window
Caldwell Catalog
Carbon Planet
Color-Magnitude Diagram (CMD)
Velocity Dispersion (σ)
Galactic Plane
H-R Diagram (HRD)
Luminosity Function (LF)
Metallicity (Z)
Mock Catalog
NGC 1866
Omega Centauri
Open Cluster
Sagittarius Dwarf Elliptical Galaxy (Sgr dE)
Star Formation History (SFH)
Star Formation Rate (SFR)
Stellar Age Determination
Turn-off Point (TO)

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