Editing Galactic corona (section)

==Current hypothetical scenario==
The hypothetical source of the galactic halo of ''coronal gas'' may be the cumulative output of many “galactic fountains” in the [[galactic disc]] ejecting hot gas.

The hypothesis is that a single [[supernova]] and then its [[supernova remnant]] both produce hot ionized gas that supplies an individual “galactic fountain”. The expelled material forms a [[superbubble|giant bubble]] of high-pressure, low density, hot gas in the denser, cooler gas and dust of the [[galactic disc]]. At least some of those bubbles extend high or low enough, vertically, to pierce through the denser disk, and form “chimneys” which exhaust the hot gas into the halo, analogous to a terrestrial [[geyser]] spewing out water and steam that is much hotter and much less dense than the surrounding earth, heated by a source hidden deep below.

As the expelled gas in the galactic corona cools, it falls back into the [[galactic disc]], guided by the disc's own gravitational attraction, enriching the [[Interstellar medium|gas and dust in the disc]] with the heavy elements (loosely termed [[metal (astronomy)|“metals”]] by astronomers) which were produced in supernova precursors, and during [[supernova]] explosions.