The terms galactic corona and gaseous corona have been used in the first decade of the 21st century to describe a hot,

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

ised, gaseous component in the

galactic halo A galactic halo is an extended, roughly spherical component of a galaxy which extends beyond the main, visible component. Several distinct components of a galaxy comprise its halo: * the stellar halo * the galactic corona (hot gas, i.e. a plas ...

of the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

. A similar body of very hot and tenuous gas in the halo of any

spiral galaxy Spiral galaxies form a galaxy morphological classification, class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''

may also be described by these terms.

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 A galactic disc (or galactic disk) is a component of disc galaxies, such as spiral galaxies like the Milky Way and lenticular galaxies. Galactic discs consist of a stellar component (composed of most of the galaxy's stars) and a gaseous compone ...

ejecting hot gas. The hypothesis is that a single

supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

and then its

supernova remnant A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar mat ...

both produce hot ionized gas that supplies an individual “galactic fountain”. The expelled material forms a giant bubble of high-pressure, low density, hot gas in the denser, cooler gas and dust of the

. 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 A geyser (, ) is a spring with an intermittent water discharge ejected turbulently and accompanied by steam. The formation of geysers is fairly rare and is caused by particular hydrogeological conditions that exist only in a few places on Ea ...

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

, guided by the disc's own gravitational attraction, enriching the gas and dust in the disc with the heavy elements (loosely termed “metals” by astronomers) which were produced in supernova precursors, and during

explosions.

Current research

Galactic coronas have been and are currently being studied extensively, in the hope of gaining a further understanding of galaxy formation. However, considering how galaxies differ in shape and size, no particular theory has been able to adequately explain how all galactic coronas are formed and maintained.

References

External links

* * * {{DEFAULTSORT:Galactic Corona Corona Corona

Current hypothetical scenario

Current research

See also

References

External links