Editing Galactic corona

{{short description|Hot, ionised, gaseous component of a galactic halo}}
{{use dmy dates |date=December 2020}}
{{inline citations |date=December 2020}}
{{incomplete citations |date=December 2020}}
The terms '''galactic corona''' and '''gaseous corona''' have been used in the first decade of the 21st&nbsp;century to describe a hot, [[ion]]ised, gaseous component in the [[galactic halo]] of the [[Milky Way]]. A similar body of very hot and tenuous gas in the halo of any [[spiral galaxy]] 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]] 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. 

==Current research==
Galactic coronas have been and are currently being studied extensively, in the hope of gaining a further understanding of galaxy formation.<ref name=Pedersen-etal-2006/><ref name=Williams-etal-2005/>
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.<ref name=Hille-2017/>

==See also==
* {{annotated link|Galaxy formation and evolution}}
* {{annotated link|Galactic coordinate system}}
* {{annotated link|bulge (astronomy)|Galactic bulge}}
* {{annotated link|Disc galaxy}}
** {{annotated link|Spiral arm}}
* {{annotated link|Galactic halo}}
* {{annotated link|Galactic spheroid}}

==References==
{{reflist|25em|refs=

<ref name=Pedersen-etal-2006>
{{cite AV media
 |collaboration=X-ray: NASA / CXC / U.&nbsp;Copenhagen; optical: Palomar DSS
 |first1=K. |last1=Pedersen
 |display-authors=etal
 |year=2006
 |title=Detection of hot halo gets theory out of hot water
 |series=NGC&nbsp;5746
 |medium=composite optical & X-ray image with expository caption
 |department=Chandra Space Telescope
 |publisher=Harvard University
 |url=http://chandra.harvard.edu/photo/2006/n5746/ |access-date=2020-12-19
}}
</ref>

<ref name=Hille-2017>
{{cite news
 |last=Hille |first=Karl
 |date=2017-09-22
 |title=Hubble's cool galaxy with a hot corona
 |website=NASA.gov
 |url=https://www.nasa.gov/image-feature/goddard/2017/hubbles-cool-galaxy-with-a-hot-corona
 |access-date=2017-09-25
}}
</ref>

<ref name=Williams-etal-2005>
{{cite arXiv
 |first1=Rik J.   |last1=Williams
 |first2=Smita    |last2=Mathur
 |first3=Fabrizio |last3=Nicastro
 |name-list-style=amp
 |year=2005
 |title=Galactic corona or Local Group intergalactic medium?
 |eprint=astro-ph/0511621
}}
</ref>

}}

==External links==
* {{cite web
 |first=Jerry |last=Bonnell
 |year=1995
 |title=The galactic corona
 |url=http://antwrp.gsfc.nasa.gov/diamond_jubilee/papers/lamb/node4.html
}}

* {{cite book
 |first=Philipp |last=Richter
 |title=How does the Galaxy Work?
 |year=2003
 |chapter=Absorption line studies in the halo
 |series=Astrophysics and Space Science Library
 |volume=315
 |pages=129–135
 |doi=10.1007/1-4020-2620-X_22
 |arxiv=astro-ph/0309693
 |isbn=1-4020-2619-6
 |s2cid=14742733
 }}

* {{cite journal
 |first1=Andrew J. |last1=Fox
 |display-authors=etal
 |year=2005
 |title=Multi-phase high-velocity clouds toward HE&nbsp;0226-4110 and PG&nbsp;0953+414
 |journal=Astrophys. J.
 |volume=630 |issue=1 |pages=332–354
 |doi=10.1086/431915
 |arxiv=astro-ph/0505299
 |bibcode=2005ApJ...630..332F
 |s2cid=2545271
 }}

{{Galaxy}}

{{DEFAULTSORT:Galactic Corona}}
[[Category:Galactic astronomy|Corona]]
[[Category:Extragalactic astronomy|Corona]]