The galactic halo is an extended, roughly spherical component of a galaxy, which extends beyond the main, visible component. It can refer to any of several distinct components which share these properties:
- 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 contrasts with the flat disc. In an elliptical galaxy, there is no sharp transition between the body of the galaxy and the halo.
Famous quotes containing the words galactic and/or halo:
“In sci-fi convention, life-forms that hadn’t developed space travel were mere prehistory—horse-shoe crabs of the cosmic scene—and something of the humiliation of being stuck on a provincial planet in a galactic backwater has stayed with me ever since.”
—Barbara Ehrenreich (b. 1941)
“There is a touch of divinity even in brutes, and a special halo about a horse, that should forever exempt him from indignities.”
—Herman Melville (1819–1891)