Galactic disk

(Last edited: Thursday, 31 August 2023, 4:11 PM)

Short Definition:

A galactic disc is a component of disc galaxies. An example are spiral galaxies and the Milky Way. The set-up of Galactic discs are a stellar component (these encompass the majority of the galaxy's stars) as well as a gaseous component (simply largely composed of cold gas and dust).

Detailed Definition:

The stellar disc of our Galaxy is divided into two components because the vertical density profile determined from star counts can be explained by a superposition of two exponentials, but not by a single exponential. (Gilmore & Reid, 1983). Further study found a thick-disc component with high-velocity dispersion, significant enrichment, and ancient age. Many writers believe that the thick disc was a relic of a turbulent period in Galactic history when the thick disc developed from accreted satellites or a thin disc heated the substance at high temperatures by one or more merger events (for a discussion, see Reddy Lambert, and Allende Prieto 2006).

This structure was first observed in external edge-on galaxies and later proposed as a distinct part of the Milky Way in a 1983 article by Gilmore and Reid. It is separate from both the thin disk and the halo. The thick disk is a structural component of approximately two-thirds of all disk galaxies, including the Milky Way. It was initially detected in external edge-on galaxies. Soon later, in the 1983 article by Gilmore and Reid, it was proposed as a galactic structure in the Milky Way, distinct from the thin disk and the halo.


The term galaxy was derived from the Greek word galaxas (kklos) (o), which means "milky (circle)," and was called by its appearance in the sky as a milky ring of light.

Sample Sentence(s):

1.     It would take two billion years for the changes caused by a Galactic Battle to be realized.

2.     It glows on the galactic scale.

3.     The galactic disk is the Milky Way's disk component.

Translations of Terms/Concepts into Partner Languages

Polish: dysk galaktyczny

French: disque galactique

German: galaktische Scheibe

Italian: disco galattico

Swedish: galaktisk skiva

» Dictionary of Space Concepts