Astrophysics (Index)About

disk galaxy

(galaxy shaped like a flat circle)

Disk galaxy is a term for disk-shaped galaxies (e.g., as opposed to elliptical galaxies), including spiral galaxies, and including galaxies that are generally disk-shaped, even if they have a bulge, e.g., lenticular galaxy. The term disk refers to the galaxy's disk-like feature, often not intended to include the protrusions of the bulge.

Some analysis of observation suggests a majority of disk galaxies (including the Milky Way) comprise two overlaid disks of stars: a thick disk (i.e., thick disk stars), and within it, a thin disk (thin disk stars) that also includes gas, and dust. The thin disk stars are apparently younger, the result of more recent star formation.

(galaxy type)
Further reading:

Referenced by pages:
circumgalactic medium (CGM)
galactic disk
galactic plane
galactic tide
galaxy classification
lenticular galaxy (S0)
Lindblad torque
Milky Way
satellite plane problem
spiral galaxy
stellar dynamics
surface density (Σ)
Toomre Q parameter (Q)