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.
Etymology
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
