The spherical cloud of stars that lies at the center of spiral galaxies.
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.
Size of nuclear bulge (Sa=large; Sc=v. small)
Openness of spiral pattern (Sa=tightly wound; Sc=v. open)
Resolution of arms into supergiant stars and HII regions (Sa=smooth, few small HII regions; Sc=clumpy, lots of bright supergiants & HII regions).
nuclear bulge nuclear force That force exerted by subatomic particles that is responsible for form, shape, and motion in the subatomic world of the nucleus. nucleic acid Substance of the DNA molecule. nucleon Either the proton or neutron inside the atomic nucleus.
@Larian LeQuella: You can see a small portion of the nuclear bulge of our Galaxy, just outside the disk of galactic dust, below the direction to the galactic center in the constellation Sagittarius.
Surrounding the central nucleus of a spiral galaxy is a large ~, which is nearly spherical in most cases and may have a diameter of up to half that of the disk.
In Hubble's classification, a spiral with a large ~ and closely coiled arms. [H76]
Hot stars of spectral types O, B, A, and early F. [H76]
A galaxy with a prominent ~ and luminous spiral arms of gas, dust, and young stars that wind out from the nucleus. Masses span the range from 1010 to 1012 M.
A spiral galaxy - not really a nebula at all (although many do appear nebulous).
They are often chaotic in appearance, with neither a ~ nor any trace of spiral arm structure. Collectively they are thought to make up about a quarter of all galaxies. Most irregular galaxies were once spiral or elliptical galaxies but were deformed by gravitational action.
5. Draw a picture of our Galaxy, both from the side and as viewed from above. Indicate the direction of the Galaxy's rotation. Label the halo, the ~, the disk, and locate the Sun in your figure.
Here's a side view
Figure 15-20a in the book provides a top view.
Population II: Stars poor in atoms heavier than helium; relatively old stars found in the halo, globular clusters, or the ~.
See also: What is the meaning of Galaxy, Bulge, Astro, Star, Orbit?