Editing Stellar corona (section)

== History ==
[[File:Solar eclipse 1806Jun16-Corona-Ferrer.png|thumb|Corona sketched by [[José Joaquín de Ferrer]] during the [[solar eclipse of June 16, 1806]] in [[Kinderhook (town), New York|Kinderhook, New York]].]]
In 1724, French-Italian astronomer [[Giacomo F. Maraldi]] recognized that the aura visible during a [[solar eclipse]] belongs to the Sun, not to the [[Moon]].<ref>{{cite encyclopedia |title=Maraldi, Giacomo Filippo |encyclopedia=Biographical Encyclopedia of Astronomers |year=2007 |publisher=Springer |location=New York |doi=10.1007/978-0-387-30400-7_899 |id= |url=https://link.springer.com/referenceworkentry/10.1007%2F978-0-387-30400-7_899 |access-date=31 October 2021 |last1=Hall |first1=Graham |last2=Elliott |first2=Ian |last3=Joeveer |first3=Mihkel |last4=Bònoli |first4=Fabrizio |last5=Langermann |first5=Y. Tzvi |last6=Casulleras |first6=Josep |last7=Sarma |first7=Ke Ve |last8=Bell |first8=Trudy E. |last9=Gurshtein |first9=Alexander A. |last10=Cunning |first10=David |last11=Wegner |first11=Gary A. |last12=Berggren |first12=Len |last13=Bònoli |first13=Fabrizio |last14=Hatch |first14=Robert Alan |last15=Jarrell |first15=Richard A. |last16=Durham |first16=Ian T. |last17=Durham |first17=Ian T. |last18=Snedegar |first18=Keith |last19=Trimble |first19=Virginia |last20=Dick |first20=Steven J. |last21=McCarthy |first21=Dennis D. |last22=Charette |first22=François |last23=Bolt |first23=Marvin |last24=Belenkiy |first24=Ari |last25=McFarland |first25=John |last26=Jackson |first26=Francine |last27=Green |first27=Daniel W. E. |last28=Ikeyama |first28=Setsuro |last29=Snedegar |first29=Keith |last30=Ogilvie |first30=Marilyn Bailey |page=736 |isbn=978-0-387-31022-0 |display-authors=1 }}</ref> In 1809, Spanish astronomer [[José Joaquín de Ferrer]] coined the term 'corona'.<ref>{{Cite journal|last=de Ferrer|first=José Joaquín|date=1809|title=Observations of the eclipse of the sun June 16th 1806 made at Kinderhook in the State of New York|url=https://books.google.com/books?id=DbkAAAAAYAAJ&pg=PA264|journal=Transactions of the American Philosophical Society|volume=6|pages=264–275|doi=10.2307/1004801|jstor=1004801}}</ref> Based on his own observations of the 1806 solar eclipse at Kinderhook (New York), de Ferrer also proposed that the corona was part of the Sun and not of the Moon. English astronomer [[Norman Lockyer]] identified the first element unknown on Earth in the Sun's chromosphere, which was called [[helium]] (from [[Greek language|Greek]] {{lang|grc-Latn|helios}} 'sun'). French astronomer [[Pierre Janssen|Jules Jenssen]] noted, after comparing his readings between the 1871 and 1878 eclipses, that the size and shape of the corona changes with the [[Solar cycle|sunspot cycle]].<ref>{{Cite web|last=Espenak|first=Fred|title=Chronology of Discoveries about the Sun|url=http://www.mreclipse.com/Totality2/TotalityApH.html|url-status=live|archive-url=https://web.archive.org/web/20201019152942/http://www.mreclipse.com/Totality2/TotalityApH.html|archive-date=19 October 2020|access-date=6 November 2020|website=Mr. Eclipse}}</ref> In 1930, [[Bernard Lyot]] invented the [[Coronagraph|"coronograph" (now "coronagraph")]], which allows viewing the corona without a total eclipse. In 1952, American astronomer [[Eugene Parker]] proposed that the solar corona might be heated by myriad tiny 'nanoflares', miniature brightenings resembling [[solar flares]] that would occur all over the surface of the Sun.

=== Historical theories ===

The high temperature of the Sun's corona gives it unusual [[spectroscopy|spectral]] features, which led some in the 19th century to suggest that it contained a previously unknown element, "[[coronium]]". Instead, these spectral features have since been explained by [[highly charged ion|highly ionized]] [[iron]] (Fe-XIV, or Fe<sup>13+</sup>).  [[Bengt Edlén]], following the work of [[Walter Grotrian]] in 1939, first identified the coronal spectral lines in 1940 (observed since 1869) as transitions from low-lying [[metastable]] levels of the ground configuration of highly ionised metals (the green Fe-XIV line from Fe<sup>13+</sup> at {{gaps|5|303|[[Ångström|Å]]}}, but also the red Fe-X line from Fe<sup>9+</sup> at {{gaps|6|374|Å}}).<ref name="Aschwanden" />