Wiktionary
n. (context astronomy English) An aggregation of individual stars, dust, and gas (and possibly dark matter) that surrounds a galaxy
Wikipedia
The galactic halo is an extended, roughly spherical component of a galaxy which extends beyond the main, visible component. Several distinct components of galaxies comprise the halo:
- the galactic spheroid ( stars)
- the galactic corona (hot gas, i.e. a plasma)
- the dark matter halo
The distinction between the halo and the main body of the galaxy is clearest in spiral galaxies, where the spherical shape of the halo contrasts with the flat disc. In an elliptical galaxy, there is no sharp transition between the body of the galaxy and the halo.
Usage examples of "galactic halo".
MACHOs, big brown dwarfs in the galactic halo, leaking radiation in the long infrared –.
Their assignment was to monitor the most important object in either Heechee or human cosmology, the kugelblitz that hung outside the galactic halo.
Extending above and beyond these spiral arms is the galactic halo, a sparsely populated region containing globular star clusters that support the more senior members of the galactic family.
The cluster was in the galactic halo and, of course, the trip was a long one.