Editing Betelgeuse (section)

===Main sequence===
[[File:Hertzsprung-Russell Diagram - ESO.png|thumb|right|[[Hertzsprung–Russell diagram]] identifying supergiants like Betelgeuse that have moved off the [[main sequence]]]]

The initial mass of Betelgeuse can only be estimated by testing different stellar evolutionary models to match its current observed properties. The unknowns of both the models and the current properties mean that there is considerable uncertainty in Betelgeuse's initial appearance, but its mass is usually estimated to have been in the range of {{solar mass|10–25}}, with modern models finding values of {{solar mass|15–20}}. Its chemical makeup can be reasonably assumed to have been around 70% hydrogen, 28% helium, and 2.4% heavy elements, slightly more metal-rich than the Sun but otherwise similar. The initial rotation rate is more uncertain, but models with slow to moderate initial rotation rates produce the best matches to Betelgeuse's current properties.<ref name=dolan2016/><ref name=vanloon/><ref name=meynet>{{cite conference |title=The past and future evolution of a star like Betelgeuse |book-title=Betelgeuse Workshop 2012 |editor=P. Kervella |volume=60 |pages=17–28 |last1=Meynet |first1=G. |last2=Haemmerlé |first2=L. |last3=Ekström |first3=S. |last4=Georgy |first4=C. |last5=Groh |first5=J. |last6=Maeder |first6=A. |year=2013 |bibcode=2013EAS....60...17M |arxiv=1303.1339 |doi=10.1051/eas/1360002 |citeseerx=10.1.1.759.5862 |s2cid=119111572}}</ref> That main sequence version of Betelgeuse would have been a hot luminous star with a spectral type such as O9V.<ref name=lebertre/>

A {{solar mass|15}} star would take between 11.5 and 15&nbsp;million years to reach the red supergiant stage, with more rapidly-rotating stars taking the longest.<ref name=meynet/> Rapidly-rotating {{solar mass|20}} stars take 9.3&nbsp;million years to reach the red supergiant stage, while {{solar mass|20}} stars with slow rotation take only 8.1&nbsp;million years.<ref name=vanloon/> These are the best estimates of Betelgeuse's current age, as the time since its [[Main sequence|zero age main sequence]] stage is estimated to be 8.0–8.5&nbsp;million years as a {{solar mass|20}} star with no rotation.<ref name=dolan2016/>