Editing Rigel (section)

== Physical characteristics ==
[[File:Hertzsprung-Russell_Diagram_-_ESO_with_Rigel.png|thumb|right|upright=1.2|alt=A chart showing several labelled stars against shaded colored areas with axes of spectral type and absolute magnitude, and Rigel labelled near the top|Rigel's place at top-center on the [[Hertzsprung–Russell diagram]]]]

Rigel is a [[blue supergiant]] that has exhausted the hydrogen fuel in its core, expanded and cooled as it moved away from the [[main sequence]] across the upper part of the [[Hertzsprung–Russell diagram]].<ref name=guinan/><ref name=seeds/> When it was on the main sequence, its [[effective temperature]] would have been around {{val|30,000|fmt=commas|ul=K}}.<ref name=saio/> Rigel's complex variability at [[Electromagnetic spectrum|visual wavelengths]] is caused by [[stellar pulsations]] similar to those of [[Deneb]]. Further observations of radial velocity variations indicate that it simultaneously oscillates in at least 19 non-radial modes with periods ranging from about 1.2 to 74 days.<ref name=apj2012_747_108/>

Estimation of many physical characteristics of blue supergiant stars, including Rigel, is challenging due to their rarity and uncertainty about how far they are from the Sun. As such, their characteristics are mainly estimated from theoretical [[Stellar evolution#Models|stellar evolution models]].<ref name=demarque2008/> Its effective temperature can be estimated from the spectral type and color to be around {{val|12,100|fmt=commas|ul=K}}.<ref name=przybilla/> A mass of {{val|21|3|u=solar mass}} at an age of {{val|8|1}}{{nbsp}}million years has been estimated by comparing evolutionary tracks, while atmospheric modeling from the spectrum gives a mass of {{solar mass|{{val|24|8}}}}.<ref name=aaa445_3_1099/>

Although Rigel is often considered the most luminous star within 1,000 light-years of the Sun,<ref name="schaaf" /><ref name=burnham/> its energy output is poorly known. Using the Hipparcos distance of {{convert|264|pc|ly|abbr=off|order=flip}}, the estimated relative luminosity for Rigel is about 120,000 times that of the Sun ({{solar luminosity|link=y}}),<ref name=apj2012_747_108/> but another recently published distance of {{convert|360|±|40|pc|ly|abbr=off|order=flip}} suggests an even higher luminosity of {{solar luminosity|219,000}}.<ref name=aaa445_3_1099/> Other calculations based on theoretical stellar evolutionary models of Rigel's atmosphere give luminosities anywhere between {{solar luminosity|83,000}} and {{solar luminosity|363,000}},<ref name=markova/> while summing the [[spectral energy distribution]] from historical photometry with the Hipparcos distance suggests a luminosity as low as {{val|61515|11486|u={{solar luminosity}}|fmt=commas}}.<ref name=baines/> A 2018 study using the [[Navy Precision Optical Interferometer]] measured the [[angular diameter]] as {{val|2.526|u=mas}}. After correcting for [[limb darkening]], the angular diameter is found to be {{val|2.606|0.009|u=mas}}, yielding a radius of {{solar radius|{{val|74.1|+6.1|-7.3}}|link=y}}.<ref name=baines/> An older measurement of the angular diameter gives {{val|2.75|0.01|u=mas}},<ref name=auf/> equivalent to a radius of {{solar radius|78.9}} at {{val|264|u=pc}}.<ref name=apj2012_747_108/> These radii are calculated assuming the Hipparcos distance of {{val|264|u=pc}}; adopting a distance of {{val|360|u=pc}} leads to a significantly larger size.<ref name=chesneau2014/> Older distance estimates were mostly far lower than modern estimates, leading to lower radius estimates; a 1922 estimate by [[John Stanley Plaskett]] gave Rigel a diameter of 25 million miles, or approximately {{Solar radius|28.9}}, smaller than its neighbor [[Aldebaran]].<ref name=plasket1922/>

Due to their closeness to each other and ambiguity of the spectrum, little is known about the intrinsic properties of the members of the Rigel BC triple system. All three stars seem to be near equally hot [[B-type main-sequence star]]s that are three to four times as massive as the Sun.<ref name=msc/>