Nuclear Bulge
The spherical cloud of stars that lies at the center of spiral galaxies.
Nucleosynthesis ...
NUCLEAR BULGE
The nuclear bulge is the central, spherical part of a spiral galaxy. It is surrounded by a disk-shaped mass of stars with spiral arms.
Surrounding the central nucleus of a spiral galaxy is a large nuclear bulge, which is nearly spherical in most cases and may have a diameter of up to half that of the disk.
At the center is the nuclear bulge (with possibly a bar) with radius of about 20,000 ly. The disk and the bulge are surrounded by the galactic halo, which is spherical and even larger than the galactic disk.
In Hubble's classification, a spiral with a large nuclear bulge and closely coiled arms. [H76]
Early-Type Stars
Hot stars of spectral types O, B, A, and early F. [H76]
Earth ...
They are often chaotic in appearance, with neither a nuclear bulge or any trace of spiral arm structure. Collectively they are thought to make up about a quarter of all galaxies.
Stars poor in atoms heavier than helium. Nearly always relatively old stars found in the halo, globular clusters, or the nuclear bulge.
precession
The slow change in the direction of Earth's axis of rotation. One cycle takes nearly 26,000 years.
As previously discussed the halo stars and globular clusters, and the nuclear bulge probably formed first, followed by the disk of our galaxy. Galaxies in general must have formed out of great clouds of gas collapsing due to their own self-gravity.
Population II: Stars poor in atoms heavier than helium; relatively old stars found in the halo, globular clusters, or the nuclear bulge.
Often the regions containing bright young stars and gas clouds are arranged in long spiral arms that can be observed to wind around the galaxy. Generally a halo of faint older stars surrounds the disk; a smaller nuclear bulge often exists, ...
 See also: Bulge, Galaxy, Orbit, Sun, Disk
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