Editing Betelgeuse (section)

=== Nascent discoveries ===
Aboriginal groups in South Australia have shared oral tales of the variable brightness of Betelgeuse for an unknown period.<ref>
{{cite news
 |last1=Boutsalis |first1=Kelly
 |date=10 August 2020
 |title=Teaching indigenous star stories
 |website=The Walrus
 |url=https://thewalrus.ca/space-teaching-indigenous-star-stories/
 |access-date=6 July 2021
}}
</ref><ref>
{{cite journal
 |last1=Hamacher |first1=Duane W.
 |year=2018
 |title=Observations of red-giant variable stars by Aboriginal Australians
 |journal=[[The Australian Journal of Anthropology]]
 |volume=29 |page=89
 |doi=10.1111/taja.12257 |arxiv=1709.04634
 |s2cid=119453488 |bibcode=2018AuJAn..29...89H
}}
</ref>

[[File:John Herschel 1846 (cropped).png|thumb|left|upright=0.8| [[John Herschel|Sir&nbsp;John Herschel]] in 1846]]
The variation in Betelgeuse's brightness was described in 1836 by [[John Herschel|Sir John Herschel]] in ''Outlines of Astronomy''. From 1836 to 1840, he noticed significant changes in magnitude when Betelgeuse outshone [[Rigel]] in October 1837 and again in November 1839.<ref name=wilk99/> A 10-year quiescent period followed; then in 1849, Herschel noted another short cycle of variability, which peaked in 1852. Later observers recorded unusually high [[Maxima and minima|maxima]] with an interval of years, but only small variations from 1957 to 1967. The records of the [[American Association of Variable Star Observers]] (AAVSO) show a maximum [[apparent magnitude|brightness]] of 0.2 in 1933 and 1942, and a minimum of 1.2, observed in 1927 and 1941.<ref name="AAVSO">
{{cite web
 | last=Davis |first=Kate
 | date=December 2000
 | title=Variable star of the month: Alpha Orionis
 | publisher=[[American Association of Variable Star Observers]] (AAVSO)
 | url=http://www.aavso.org/vsots_alphaori
 | access-date=10 July 2010
}}
</ref><ref name=BURNHAM>
{{cite book
 | first=Robert Jr. | last=Burnham | author-link=Robert Burnham Jr.
 | year=1978
 | title=Burnham's Celestial Handbook: An observer's guide to the universe beyond the Solar system
 | volume=2
 | publisher=Courier Dover Publications
 | location=New York, NY
 | isbn=978-0-486-23568-4
 | url=https://archive.org/details/burnhamscelestia02robe
 | url-access=registration
 | page=[https://archive.org/details/burnhamscelestia02robe/page/1290 1290]
}}
</ref> This variability in brightness may explain why [[Johann Bayer]], with the publication of his ''[[Uranometria]]'' in 1603, designated the star ''alpha'', as it probably rivaled the usually brighter Rigel (''beta'').<ref name="100greatest">
{{cite book
 | last=Kaler |first= James B.
 | year=2002
 | title=The Hundred Greatest Stars
 | publisher=Copernicus Books
 | location=New York, NY
 | isbn=978-0-387-95436-3
 | page=33
}}
</ref> From Arctic latitudes, Betelgeuse's red colour and higher location in the sky than Rigel meant the [[Inuit]] regarded it as brighter, and one local name was ''Ulluriajjuaq'' ("large star").<ref name=inuit>
{{cite book
 |last = MacDonald |first = John
 |year = 1998
 |title = The Arctic sky: Inuit astronomy, star lore, and legend
 |publisher = Royal Ontario Museum / Nunavut Research Institute
 |location = Toronto, Ontario / Iqaluit, NWT
 |isbn = 978-0-88854-427-8
 |url = https://archive.org/details/arcticskyinuitas0000macd/page/52
 |url-access = registration
 |pages = [https://archive.org/details/arcticskyinuitas0000macd/page/52 52–54, 119]
}}
</ref>

In 1920, [[Albert A. Michelson]] and [[Francis G. Pease]] mounted a six-meter [[Interferometry|interferometer]] on the front of the 2.5-meter telescope at [[Mount Wilson Observatory]], helped by [[John August Anderson]]. The trio measured the angular diameter of Betelgeuse at 0.047[[arcsecond|″]], a figure that resulted in a diameter of {{val|3.84|e=8|u=km}} ({{val|2.58|ul=AU}}) based on the [[stellar parallax|parallax]] value of {{val|0.018|ul="}}.<ref name=MICHELSON>
{{cite journal
 |last1=Michelson |first1=A.A. |author1-link=Albert Abraham Michelson
 |last2=Pease |first2=F.G. |author2-link=Francis G. Pease
 |year=1921
 |title=Measurement of the diameter of Alpha Orionis with the interferometer
 |journal=[[Astrophysical Journal]]
 |volume=53 |issue=5 |pages=249–259
 |bibcode=1921ApJ....53..249M
 |doi=10.1086/142603 |pmid=16586823
 |pmc=1084808 |s2cid=21969744
|quote=The 0.047&nbsp;arcsecond measurement was for a uniform disk. In the article Michelson notes that limb darkening would increase the angular diameter by about 17%, hence 0.055&nbsp;arcseconds.
}}
</ref> But limb darkening and measurement errors resulted in uncertainty about the accuracy of these measurements.

The 1950s and 1960s saw two developments that affected stellar [[convection]] theory in red supergiants: the [[Stratoscope]] projects and the 1958 publication of ''Structure and Evolution of the Stars'', principally the work of [[Martin Schwarzschild]] and his colleague at [[Princeton University]], Richard Härm.<ref name=BRUCEMEDAL>
{{cite web
 | last=Tenn |first = Joseph S.
 | date=June 2009
 | title=Martin Schwarzschild 1965
 | series=The Bruce Medalists
 | publisher=[[Astronomical Society of the Pacific]] (ASP)
 | url=http://www.phys-astro.sonoma.edu/BruceMedalists/
 | access-date=28 September 2010
}}
</ref><ref name=SCHWARZSCHILD1958>
{{cite book
 | last=Schwarzschild |first=M. |author-link=Martin Schwarzschild
 | year=1958
 | title=Structure and Evolution of the Stars
 | publisher=Princeton University Press
 | bibcode=1958ses..book.....S
 | isbn=978-0-486-61479-3
 | url=https://archive.org/details/StructureAndEvolutionOfTheStars
 | url-access=registration
}}
</ref>
This book disseminated ideas on how to apply computer technologies to create stellar models, while the Stratoscope projects, by taking balloon-borne telescopes above the Earth's [[Wave turbulence|turbulence]], produced some of the finest images of [[solar granule]]s and [[sunspot]]s ever seen, thus confirming the existence of convection in the solar atmosphere.<ref name=BRUCEMEDAL/>
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