Editing Stellar atmosphere (section)

==Overview==
The stellar atmosphere is divided into several regions of distinct character:

* The [[photosphere]], which is the atmosphere's lowest and coolest layer, is normally its only visible part.<ref name="BrightPS"/> [[Light]] escaping from the surface of the star stems from this region and passes through the higher layers. The [[Sun]]'s photosphere has a [[effective temperature|temperature]] in the {{cvt|5,770|–|5,780|K|C F |lk=on}} range.<ref name="lowTemp">{{cite book |last=Mariska|first=J. T. |title=The solar transition region |series=Cambridge Astrophysics Series  |url=https://cambridge.org/catalogue/catalogue.asp?isbn=9780521382618&ss=toc |publisher=[[Cambridge University Press]] |isbn=978-0-521-38261-8 |year=1992}}</ref><ref name = "higherTemp"/> [[Starspot]]s, cool regions of disrupted [[magnetic field]], lie in the photosphere.<ref name = "higherTemp">{{cite book |last=Lang|first=K. R. |title= Sun, earth, and sky |edition=2nd |date=September 2006  |publisher=Springer |isbn=978-0-387-30456-4  |page=81 |chapter=5.1 MAGNETIC FIELDS IN THE VISIBLE PHOTOSPHERE |quote=this opaque layer is the photosphere, the level of the Sun from which we get our light and heat}}</ref>
* Above the photosphere lies the [[chromosphere]]. This part of the atmosphere first cools down and then starts to heat up to about 10 times the temperature of the photosphere.
* Above the chromosphere lies the [[solar transition region|transition region]], where the temperature increases rapidly on a distance of only around {{cvt|100|km|mi}}.<ref>{{cite book |last=Mariska|first=J. T. |title=The solar transition region |isbn=978-0-521-38261-8 |page=60 |quote=100 km suggested by average models |year=1992|publisher=Cambridge University Press }}</ref>
* Additionally, many stars have a molecular layer (MOLsphere) above the photosphere and just beyond or even within the chromosphere.<ref>{{cite journal | doi=10.1086/504585 | title=Infrared Spectra and Visibilities as Probes of the Outer Atmospheres of Red Supergiant Stars | year=2006 | last1=Tsuji | first1=Takashi | journal=The Astrophysical Journal | volume=645 | issue=2 | pages=1448–1463 | s2cid=119426022 | doi-access=free }}</ref> The molecular layer is cool enough to contain molecules rather than plasma, and may consist of such components as carbon monoxide, water vapor, silicon monoxide, and titanium oxide.
* The outermost part of the stellar atmosphere, or upper stellar atmosphere, is the [[stellar corona|corona]], a tenuous [[plasma (physics)|plasma]] which has a temperature above one million Kelvin.<ref>{{Cite journal|author= R.C. Altrock |date=  2004 |title= The Temperature of the Low Corona During Solar Cycles 21–23  |journal= Solar Physics   |volume= 224 |issue= 1–2 |page = 255  |doi= 10.1007/s11207-005-6502-4 |bibcode = 2004SoPh..224..255A |s2cid= 121468084 |url= https://zenodo.org/record/1232838 }}</ref> While all stars on the [[main sequence]] feature transition regions and coronae, not all [[Stellar evolution|evolved stars]] do so. It seems that only some [[giant star|giants]], and very few [[supergiant]]s, possess coronae. [[Stellar corona#Coronal heating problem|An unresolved problem]] in stellar [[astrophysics]] is how the corona can be heated to such high temperatures. The answer is believed to lie in [[magnetic field]]s, but the exact mechanism remains unclear.<ref>{{Cite web|url= http://imagine.gsfc.nasa.gov/docs/science/mysteries_l1/corona.html |title= The Sun's Corona – Introduction   |publisher= [[NASA]] |access-date= 2010-05-21 | quote = Now most scientists believe that the heating of the corona is linked to the interaction of the magnetic field lines.}}</ref>
* The [[astrosphere]], which is in the case of the Sun the [[heliosphere]],<ref name="Sterken Baalmann Draine Godenko 2022 p. ">{{cite journal | last=Sterken | first=Veerle J. | last2=Baalmann | first2=Lennart R. | last3=Draine | first3=Bruce T. | last4=Godenko | first4=Egor | last5=Herbst | first5=Konstantin | last6=Hsu | first6=Hsiang-Wen | last7=Hunziker | first7=Silvan | last8=Izmodenov | first8=Vladislav | last9=Lallement | first9=Rosine | last10=Slavin | first10=Jonathan D. | title=Dust in and Around the Heliosphere and Astrospheres | journal=Space Science Reviews | publisher=Springer Science and Business Media LLC | volume=218 | issue=8 | year=2022 | issn=0038-6308 | doi=10.1007/s11214-022-00939-7 | page=| doi-access=free | hdl=20.500.11850/585419 | hdl-access=free }}</ref> can be in a broader understanding considered the furthest part of a stellar atmosphere,<ref name="NASA Science 2017 b915">{{cite web | title=Sun: Facts | website=NASA Science | date=2017-11-14 | url=https://science.nasa.gov/sun/facts/ | access-date=2023-10-11}}</ref><ref name="NASA 2013 z570">{{cite web | title=Components of the Heliosphere | website=NASA | date=2013-01-25 | url=https://www.nasa.gov/image-article/components-of-heliosphere/#:~:text=influence%20in%20space.-,The%20Heliosphere%20is%20the%20outer%20atmosphere%20of%20the%20Sun%20and,planets%20in%20our%20solar%20system. | access-date=2023-10-11}}</ref> before [[interstellar space]] begins at the [[Heliopause (astronomy)|heliopause]]. The astrosphere is not to be confused with the [[Solar System]] and its outermost region the [[Oort cloud]], which extends much further than the astrosphere, therefore far into interstellar space.

During a total [[solar eclipse]], the photosphere of the Sun is [[occultation|obscured]], revealing its atmosphere's other layers.<ref name = "BrightPS">
{{Cite web|url= https://www.sciencedaily.com/releases/1999/08/990805111308.htm |title= "Beyond the Blue Horizon" – A Total Solar Eclipse Chase | date=1999-08-05 |access-date= 2010-05-21 | quote = On ordinary days, the corona is hidden by the blue sky, since it is about a million times fainter than the layer of the sun we see shining every day, the photosphere.}}</ref> Observed during eclipse, the Sun's chromosphere appears (briefly) as a thin pinkish [[arc (geometry)|arc]],<ref>
{{Cite book|last1= Lewis |first1= J.S. |title= Physics and chemistry of the solar system | publisher = Elsevier Academic Press |edition= Second |date= 2004-02-23 |isbn= 978-0-12-446744-6 | quote = The dominant color is influenced by the [[Balmer series|Balmer radiation]] of atomic hydrogen  |page= 87 }}
</ref> and its corona is seen as a tufted [[Halo (optical phenomenon)|halo]]. The same phenomenon in [[Binary star#Eclipsing binaries|eclipsing binaries]] can make the chromosphere of giant stars visible.<ref>
{{Cite book|last1= Griffin |first1= R.E. |editor1-first= W.I. |editor1-last= Hartkopft |editor2-first= E.F. |editor2-last= Guinan |title= Only Binary Stars Can Help Us Actually SEE a Stellar Chromosphere   |journal= Proceedings of the International Astronomical Union |volume= 2 |edition= 1  |date=  2007-08-27  |publisher= Cambridge University Press  |isbn=  978-0-521-86348-3 |doi= 10.1017/S1743921307006163
 |page= 460  |s2cid= 123028350 }}

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