Stellar Populations
Since most globular clusters formed in the early stages of the universe,
they are composed of the ancient Population II
stars (right panel), which are low in metals.
The younger
Population I
stars are found primarily in the disks of spiral galaxies, where repeated stages of
star formation and nuclear burning of hydrogen and helium into heavier elements
have taken place.
The Galactic Halo
The globular clusters lie in a spherical outer halo of our galaxy and seldom
encounter the galactic disk. The above right image shows
the distribution of some globular clusters in the Milky Way, plotted in galactic coordinates with the
center of the galaxy at the center of the diagram and the disk of
the galaxy indicated by the horizontal line. Clearly the globular clusters have a very different
distribution than that of the disk stars.
The following figure is a schematic picture of our galaxy showing the halo with
globular
clusters.
