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'''Rigel''' ({{IPAc-en|ˈ|r|aɪ|dʒ|əl|,_|-|g|əl}}), also designated '''β Orionis''' ([[Latinisation of names|Latinized]] to '''Beta Orionis''', abbreviated '''Beta Ori''', '''β Ori'''), is a [[variable star]]. It is, on average, the [[list of brightest stars|seventh-brightest star]] in the [[night sky]] and the brightest star in the [[constellation]] of [[Orion (constellation)|Orion]]—though occasionally it is outshone within the constellation by [[Betelgeuse]], another variable star. The [[apparent magnitude]] of Rigel varies irregularly between +0.05 and +0.18.
'''Rigel''' ({{IPAc-en|ˈ|r|aɪ|dʒ|əl|,_|-|g|əl}}), also designated '''β Orionis''' ([[Latinisation of names|Latinized]] to '''Beta Orionis''', abbreviated '''Beta Ori''', '''β Ori'''), is a [[variable star]]. It is, on average, the [[list of brightest stars|seventh-brightest star]] in the [[night sky]] and the brightest star in the [[constellation]] of [[Orion (constellation)|Orion]]—though occasionally it is outshone within the constellation by [[Betelgeuse]], another variable star. The [[apparent magnitude]] of Rigel varies irregularly between +0.05 and +0.18.


Although appearing as a single star to the naked eye, Rigel is actually a multiple [[star system]]. The name ''Rigel'' strictly refers to the brightest component of this system. It is a [[Massive star|massive]] [[blue-white supergiant]] estimated to be anywhere from 61,500 to 363,000 times [[Solar luminosity|as luminous as the Sun]], depending on the method used to calculate its properties and assumptions about its distance, thought to be about {{convert|860|ly|pc|sigfig=2}}. Rigel has exhausted the [[hydrogen]] in its core, causing the star to expand; its radius is over 70 times that of the [[Solar radius|Sun]]. Pulsations cause Rigel's small intrinsic brightness variation; it is classified as an [[Alpha Cygni variable]].
Although appearing as a single star to the naked eye, Rigel is actually a multiple [[star system]]. The name ''Rigel'' strictly refers to the brightest component of this system. It is a [[Massive star|massive]] [[blue-white supergiant]] estimated to be anywhere from 61,500 to 363,000 times [[Solar luminosity|as luminous as the Sun]], depending on the method used to calculate its properties and assumptions about its distance, thought to be about {{convert|860|ly|pc|order=flip|sigfig=2}}. Rigel has started to exhaust [[hydrogen]] in its core, causing the star to expand; its radius is over 70 times that of the [[Solar radius|Sun]]. Pulsations cause Rigel's small intrinsic brightness variation; it is classified as an [[Alpha Cygni variable]].


Rigel's brightest companion is itself a likely [[triple star system]], separated from Rigel by {{val|9.5|ul="}}. Often referred to as Rigel B, it has a combined apparent magnitude of 6.7 but is still over 400 times fainter than the primary star and visible only with a telescope. Rigel B is a [[spectroscopic binary]] composed of the components Ba and Bb. It also has a very close visual companion, component C, of almost equal brightness to B.
Rigel's brightest companion is itself a likely [[triple star system]], separated from Rigel by {{val|9.5|ul="}}. Often referred to as Rigel B, it has a combined apparent magnitude of 6.7 but is still over 400 times fainter than the primary star and visible only with a telescope. Rigel B is a [[spectroscopic binary]] composed of the components Ba and Bb. It also has a very close visual companion, component C, of almost equal brightness to B.


== Nomenclature ==
== Nomenclature ==
The modern name ''Rigel'' was likely first recorded in the [[Alfonsine Tables]] of 1521. It is derived from the Arabic name ''{{transl|ar|Rijl Jauzah al Yusrā}}'', "the left leg (foot) of Jauzah" (i.e. ''rijl'' meaning "leg, foot"),<ref name=allen/> which can be traced to the 10th century.<ref name="KUNITZSCH1959"/> "Jauzah" was a proper name of the Orion figure, an alternative Arabic name was {{lang|ar|رجل الجبار}} ''{{transl|ar|riǧl al-ǧabbār}}'', "the foot of the great one", which is the source of the rarely used variant names ''Algebar'' or ''Elgebar''. The ''Alphonsine Tables'' saw its name split into "Rigel" and "Algebar", with the note, ''et dicitur Algebar. Nominatur etiam Rigel.''<ref name=Kunitzsch86/> Alternate spellings from the 17th century include ''Regel'' by Italian astronomer [[Giovanni Battista Riccioli]], ''Riglon'' by German astronomer [[Wilhelm Schickard]], and ''Rigel Algeuze'' or ''Algibbar'' by English scholar [[Edmund Chilmead]].<ref name="allen"/> In 2016, the [[International Astronomical Union]] officially recognized Rigel for β Orionis A, the blue supergiant component visible to the [[naked eye]].<ref name="IAU-CSN"/>
The name ''Rigel'' was likely first recorded in the [[Alfonsine Tables]] of 1521. It is derived from the Arabic name ''{{transl|ar|Rijl Jauzah al Yusrā}}'', "the left leg (foot) of Jauzah" (i.e. ''rijl'' meaning "leg, foot"),<ref name=allen/> which can be traced to the 10th century.<ref name="KUNITZSCH1959"/> "Jauzah" was a proper name of the Orion figure, an alternative Arabic name was {{lang|ar|رجل الجبار}} ''{{transl|ar|riǧl al-ǧabbār}}'', "the foot of the great one", which is the source of the rarely used variant names ''Algebar'' or ''Elgebar''. The ''Alphonsine Tables'' saw its name split into "Rigel" and "Algebar", with the note, ''et dicitur Algebar. Nominatur etiam Rigel.''<ref name=Kunitzsch86/> Alternate spellings from the 17th century include ''Regel'' by Italian astronomer [[Giovanni Battista Riccioli]], ''Riglon'' by German astronomer [[Wilhelm Schickard]], and ''Rigel Algeuze'' or ''Algibbar'' by English scholar [[Edmund Chilmead]].<ref name="allen"/> In 2016, the [[International Astronomical Union]] officially recognized Rigel for β Orionis A, the blue supergiant component visible to the [[naked eye]].<ref name="IAU-CSN"/>


''β Orionis'' ([[Latinisation of names|Latinized]] to ''Beta Orionis'') is the star's [[Bayer designation]], although it is usually the brightest star in Orion. Astronomer [[James B. Kaler]] has speculated that perhaps Rigel was designated by Bayer during a rare period where it was outshone by the variable star Betelgeuse, resulting in the latter star being designated ''alpha'' and Rigel designated ''beta''.<ref name="kalerrigel"/> Rigel is included in the [[General Catalogue of Variable Stars]], but since it already has a Bayer designation, β Orionis, it has no separate [[variable star designation]].<ref name=baa/>
''β Orionis'' ([[Latinisation of names|Latinized]] to ''Beta Orionis'') is the star's [[Bayer designation]], although it is usually the brightest star in Orion. Astronomer [[James B. Kaler]] has speculated that perhaps Rigel was designated by Bayer during a rare period where it was outshone by the variable star Betelgeuse, resulting in the latter star being designated ''alpha'' and Rigel designated ''beta''.<ref name="kalerrigel"/> Rigel is included in the [[General Catalogue of Variable Stars]], but since it already has a Bayer designation, β Orionis, it has no separate [[variable star designation]].<ref name=baa/>
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Rigel is the seventh-brightest star in the [[celestial sphere]] excluding the Sun. It is usually fainter than [[Capella (star)|Capella]],<ref name="schaaf"/> although both are slightly variable in brightness. Rigel is an irregular [[pulsating variable]] with a range in [[apparent magnitude]] from 0.05 to 0.18.<ref name=guinan/> Although Rigel has the [[Bayer designation]] "beta", it is almost always brighter than Alpha Orionis ([[Betelgeuse]]).<ref name="schaaf"/> Since 1943, the [[stellar spectrum|spectrum]] of this star has served as a spectral reference for class B8Ia, for use as a comparison when [[Stellar classification|classifying]] the spectra of other stars.<ref name=mkk/><ref name=baas25_1319/> Rigel appears slightly blue-white, almost white, and has a (B–V) [[color index]] of −0.06.<ref name="csiro"/>
Rigel is the seventh-brightest star in the [[celestial sphere]] excluding the Sun. It is usually fainter than [[Capella (star)|Capella]],<ref name="schaaf"/> although both are slightly variable in brightness. Rigel is an irregular [[pulsating variable]] with a range in [[apparent magnitude]] from 0.05 to 0.18.<ref name=guinan/> Although Rigel has the [[Bayer designation]] "beta", it is almost always brighter than Alpha Orionis ([[Betelgeuse]]).<ref name="schaaf"/> Since 1943, the [[stellar spectrum|spectrum]] of this star has served as a spectral reference for class B8Ia, for use as a comparison when [[Stellar classification|classifying]] the spectra of other stars.<ref name=mkk/><ref name=baas25_1319/> Rigel appears slightly blue-white, almost white, and has a (B–V) [[color index]] of −0.06.<ref name="csiro"/>


Culminating at midnight on 12 December, and at 9 pm on 24 January, Rigel is visible in winter evenings in the [[northern hemisphere]] and summer in the southern.<ref name="schaaf"/> In the [[southern hemisphere]], Rigel is the first bright star of Orion visible as the constellation rises.<ref name=ellyard/> The star forms a vertex of the "[[Winter Hexagon]]", an [[asterism (astronomy)|asterism]] that includes [[Aldebaran]], Capella, [[Pollux (star)|Pollux]], [[Procyon]], and [[Sirius]]. This formation is visible from most locations on Earth and is prominent in the night sky from December through March.<ref name=Penprase2010/> Rigel is one of the most important [[nautical almanac|stars used in navigation]], since it is bright, easily located and equatorial, which means it is visible all around the world's oceans (the exception is the area within 8° of the [[North Pole]]).<ref name=kerigan/>
Culminating at midnight on 12 December, and at 9 pm on 24 January, Rigel is visible in winter evenings in the [[northern hemisphere]] and summer in the southern.<ref name="schaaf"/> In the [[southern hemisphere]], Rigel is the first bright star of Orion visible as the constellation rises.<ref name=ellyard/> The star forms a vertex of the "[[Winter Hexagon]]", an [[asterism (astronomy)|asterism]] that includes [[Aldebaran]], Capella, [[Pollux (star)|Pollux]], [[Procyon]], and [[Sirius]]. This formation is visible from most locations on Earth and is prominent in the night sky from December through March.<ref name=Penprase2010/> Rigel is a recognised equatorial [[nautical almanac|navigation star]], being easily located and readily visible in all the world's oceans (the exception is the area within 8° of the [[North Pole]]).<ref name=kerigan/>


=== Spectroscopy ===
=== Spectroscopy ===
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In 1933, the [[Hα]] spectral line was seen to be unusually weak and shifted {{val|0.1|ul=nm}} towards shorter wavelengths, while there was a narrow [[emission line|emission spike]] about {{val|1.5|u=nm}} to the long wavelength side of the main absorption line.<ref name=struve/> This is now known as a [[P Cygni profile]] after a star that shows this feature strongly in its spectrum. It is associated with strong mass loss where there is simultaneously emission from dense wind close to the star and absorption from circumstellar material expanding away from the star.<ref name=struve/>
In 1933, the [[Hα]] spectral line was seen to be unusually weak and shifted {{val|0.1|ul=nm}} towards shorter wavelengths, while there was a narrow [[emission line|emission spike]] about {{val|1.5|u=nm}} to the long wavelength side of the main absorption line.<ref name=struve/> This is now known as a [[P Cygni profile]] after a star that shows this feature strongly in its spectrum. It is associated with strong mass loss where there is simultaneously emission from dense wind close to the star and absorption from circumstellar material expanding away from the star.<ref name=struve/>


The unusual Hα line profile has since been observed to vary unpredictably: around a third of the time it is a normal absorption line; about a quarter of the time it is a double-peaked line, that is an absorption line with an emission core or an emission line with an absorption core; about a quarter of the time it has a P Cygni profile; most of the rest of the time the line has an inverse P Cygni profile, where the emission component is on the short wavelength side of the line; rarely there is a pure emission Hα line.<ref name=morrison/> The line profile changes are interpreted as variations in the quantity and velocity of material being expelled from the star. Occasional very high velocity outflows are inferred, and, more rarely, infalling material. The overall picture is one of large [[coronal loop|looping structures]] arising from the [[photosphere]] and driven by magnetic fields.<ref name=israelian/>
The unusual Hα line profile has since been observed to vary unpredictably: around a third of the time it is a normal absorption line; about a quarter of the time it is a double-peaked line, that is an absorption line with an emission core or an emission line with an absorption core; about a quarter of the time it has a P Cygni profile; most of the rest of the time the line has an inverse P Cygni profile, where the emission component is on the short wavelength side of the line; rarely there is a pure emission Hα line.<ref name=morrison/> The line profile changes are interpreted as variations in the quantity and velocity of material being expelled from the star. Occasional very high velocity outflows have been observed, and, more rarely, infalling material. The overall picture is one of large [[coronal loop|looping structures]] arising from the [[photosphere]] and driven by magnetic fields.<ref name=israelian/>


The variations in the spectrum have been reflected in published spectral classes, such as B8 Ia, B8 Iab, and B8 Iae.<ref name=schultz/><ref name=bally/>
The variations in the spectrum have been reflected in published spectral classes, such as B8 Ia, B8 Iab, and B8 Iae.<ref name=schultz/><ref name=bally/>
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=== Mass loss ===
=== Mass loss ===
From observations of the Hα spectral line, the mass loss from Rigel is estimated to be {{val|1.5|0.4|e=−7}} solar masses per year ({{solar mass}}/yr), around ten million times more than the mass loss from the [[Sun]].<ref name=chesneau2010/> More detailed optical and [[K band (infrared)|K band]] infrared spectroscopic observations, together with [[VLTI]] interferometry, were taken from 2006 to 2010. Analysis of the Hα and [[Hγ]] spectral line profiles, and measurement of the regions producing the lines, show that the [[stellar wind]] varies greatly in structure and strength. Loop and arm structures were also detected within the wind. Calculations of mass loss from the Hγ line give {{val|9.4|0.9|e=−7}} {{solar mass}}/yr in 2006-7 and {{val|7.6|1.1|e=−7}} {{solar mass}}/yr in 2009-10. Calculations using the Hα line give lower results, around {{val|1.5|e=−7}} {{solar mass}}/yr. The terminal wind velocity is 300&nbsp;km·s<sup>−1</sup>.<ref name=chesneau2014/>
From spectroscopic observations of the variable Hα spectral line, the mass loss from Rigel is estimated to be {{val|1.5|0.4|e=−7}} solar masses per year ({{solar mass}}/yr), around ten million times more than the mass loss from the [[Sun]].<ref name=chesneau2010/> More detailed optical and [[K band (infrared)|K band]] infrared spectroscopic observations, together with [[VLTI]] interferometry, were taken from 2006 to 2010. Analysis of the Hα and [[Hγ]] line profiles, and measurement of the regions producing the lines, show that the [[stellar wind]] varies greatly in structure and strength. Loop and arm structures were also detected within the wind. Calculations of mass loss from the Hγ line give {{val|9.4|0.9|e=−7}} {{solar mass}}/yr in 2006-7 and {{val|7.6|1.1|e=−7}} {{solar mass}}/yr in 2009-10. Calculations using the Hα line give lower results, around {{val|1.5|e=−7}} {{solar mass}}/yr. The terminal wind velocity is 300&nbsp;km·s<sup>−1</sup>.<ref name=chesneau2014/>


==Distance==
==Distance==
[[File:Treasures3.jpg|thumb|right|Rigel and [[reflection nebula]] [[IC 2118]] in [[Eridanus (constellation)|Eridanus]]. Rigel B is not visible in the glare of the main star.]]
[[File:Treasures3.jpg|thumb|right|Rigel and [[reflection nebula]] [[IC 2118]] in [[Eridanus (constellation)|Eridanus]]. Rigel B is not visible in the glare of the main star.]]
The distance to Rigel has been difficult to estimate with accuracy, as its brightness is not easy to determine independently, and it is too distant for accurate [[parallax]] measurements. As it is both bright and moving through a region of nebulosity, Rigel lights up several dust clouds in its vicinity, most notably the 5°<ref name=Guieu2010/>–long [[IC 2118]] (the Witch Head Nebula),<ref name="Jedicke1992"/> located at an [[angular separation]] of 2.5° from the star.<ref name=Guieu2010/> These are thought to be about {{convert|40|ly|pc|abbr=off}} distant from the star itself.<ref name="kalerrigel"/> For stars associated with this nebulosity, a distance of {{convert|291|±|2|pc|ly|0|abbr=off|order=flip}} is estimated.<ref name=Kounkel2018/>
An accurate distance for Rigel is difficult to independently determine due to the star's brightness and small measured [[parallax]]. Other indirect distant methods have been recently employed. For example, Rigel is believed to be moving through a region of nebulosity whose brightness lights up several dust clouds in its vicinity. Most notably of these is the 5°<ref name=Guieu2010/>–long [[IC 2118]] (the Witch Head Nebula),<ref name="Jedicke1992"/> located at an [[angular separation]] of 2.5° from the star, <ref name=Guieu2010/> and are thought to be about {{convert|40|ly|pc|abbr=off}} away.<ref name="kalerrigel"/> Measures of other nebula embedded stars estimate Rigel's distance to be {{convert|291|±|2|pc|ly|0|abbr=off|order=flip}}.<ref name=Kounkel2018/>


Rigel has been classified as an outlying member of the [[Orion OB1 Association]], which is located at a distance of up to {{convert|500|pc|ly|abbr=off|order=flip}} from Earth. It has also been listed as a member of the poorly-defined [[Taurus-Orion R1 Association]], somewhat closer at {{convert|360|pc|ly|abbr=off|order=flip}}.<ref name=markova/><ref name=racine/> Rigel is thought to be considerably closer than most of the members of Orion OB1 and the [[Orion Nebula]]. [[Betelgeuse]] and [[Saiph]] lie at a similar distance as Rigel, although Betelgeuse is a [[runaway star]] with a complex history and might have originally formed in the main body of the association.<ref name=bally/>
Rigel has been classified as an outlying member of the [[Orion OB1 Association]], which is located at a distance of up to {{convert|500|pc|ly|abbr=off|order=flip}} from Earth. It has also been listed as a member of the poorly-defined [[Taurus-Orion R1 Association]], somewhat closer at {{convert|360|pc|ly|abbr=off|order=flip}}.<ref name=markova/><ref name=racine/> Rigel is thought to be considerably closer than most of the members of Orion OB1 and the [[Orion Nebula]]. [[Betelgeuse]] and [[Saiph]] lie at a similar distance as Rigel, although Betelgeuse is a [[runaway star]] with a complex history and might have originally formed in the main body of the association.<ref name=bally/>
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At Rigel's estimated distance, β Ori B's [[projected separation]] from its primary is over 2,200&nbsp;[[astronomical unit|AU]]. Since its discovery, there has been no sign of orbital motion, although both stars share similar [[proper motion|common proper motion]].<ref name=sb9/><ref name="Jedicke1992"/> The pair would have a minimum orbital period of around 18,000&nbsp;years.<ref name=msc/> [[Gaia Data Release 2]] (DR2) contains a somewhat unreliable parallax for β Ori B, placing it at about {{convert|340|pc|ly|abbr=off|order=flip}}, further away than the Hipparcos distance for Rigel, but similar to the Taurus-Orion R1 association. There is no parallax for Rigel in Gaia DR2. The Gaia DR2 proper motions for β Ori B and the Hipparcos proper motions for Rigel are both small, although not quite the same.<ref name=dr2b/>
At Rigel's estimated distance, β Ori B's [[projected separation]] from its primary is over 2,200&nbsp;[[astronomical unit|AU]]. Since its discovery, there has been no sign of orbital motion, although both stars share similar [[proper motion|common proper motion]].<ref name=sb9/><ref name="Jedicke1992"/> The pair would have a minimum orbital period of around 18,000&nbsp;years.<ref name=msc/> [[Gaia Data Release 2]] (DR2) contains a somewhat unreliable parallax for β Ori B, placing it at about {{convert|340|pc|ly|abbr=off|order=flip}}, further away than the Hipparcos distance for Rigel, but similar to the Taurus-Orion R1 association. There is no parallax for Rigel in Gaia DR2. The Gaia DR2 proper motions for β Ori B and the Hipparcos proper motions for Rigel are both small, although not quite the same.<ref name=dr2b/>


in 1871, [[Sherburne Wesley Burnham]] suspected β Ori B to be double, and in 1878, he resolved it into two nearly equal components.<ref name=aitken/> Their measured separation varies from less than 0.1" to nearly 0.2". In 2009, [[speckle interferometric|speckle interferometry]] showed two almost identical components separated by 0.124".<ref name=mason/> The companion is designated as component C (β Ori C). Both stars have apparent visual magnitudes of 7.6. Their derived orbital period is 63&nbsp;years.<ref name=msc/>
In 1871, [[Sherburne Wesley Burnham]] suspected β Ori B to be double, and in 1878, he resolved it into two nearly equal components.<ref name=aitken/> Their measured separation varies from less than 0.1" to nearly 0.2". In 2009, [[speckle interferometric|speckle interferometry]] showed two almost identical components separated by 0.124".<ref name=mason/> The companion is designated as component C (β Ori C).{{clarify |date=March 2019 |reason=The notation in the parentheses needs clarification for the reader.}} Both stars have apparent visual magnitudes of 7.6. Their derived orbital period is 63&nbsp;years.<ref name=msc/>


β Ori B appears to be a double-lined [[spectroscopic binary]] system, which indicates that the individual [[absorption line]]s of both components is visible in the [[stellar spectrum|spectrum]]. It consists of two [[main sequence]] stars that orbit each other every 9.86&nbsp;days. These two stars do not seem to correspond to the visual binary components B and C, so the BC sub-system might be a triple, although the actual arrangement is unclear.<ref name=sb9/><ref name=sanford/>
β Ori B appears to be a double-lined [[spectroscopic binary]] system, which indicates that the individual [[absorption line]]s of both components is visible in the [[stellar spectrum|spectrum]]. It consists of two [[main sequence]] stars that orbit each other every 9.86&nbsp;days. These two stars do not seem to correspond to the visual binary components B and C, so the BC sub-system might be a triple, although the actual arrangement is unclear.<ref name=sb9/><ref name=sanford/>


In 1878, Burnham found a nearby 15th magnitude star, catalogued as component D (β Ori D), whose 2017 separation from Rigel was {{val|44.5|ul="}} almost due north at position angle of 1°,<ref name=WDS/> although it is unclear whether it is physically related or a coincidental alignment. Gaia DR2 finds it to be a 12th magnitude sunlike star at approximately the same distance as Rigel.<ref name=dr2d/> Most likely to be an orange dwarf, this star would have an orbital period of around 250,000 years, if it is part of the stellar system.<ref name="kalerrigel"/>
In 1878, Burnham found a further nearby 15th magnitude star, catalogued as component D (β Ori D){{clarify |date=March 2019 |reason=The notation in the parentheses needs clarification for the reader.}} , whose 2017 separation from Rigel was {{val|44.5|ul="}} almost due north at position angle of 1°,<ref name=WDS/> although it is unclear whether it is physically related or a coincidental alignment. Gaia DR2 finds it to be a 12th magnitude sunlike star at approximately the same distance as Rigel.<ref name=dr2d/> Most likely to be an orange dwarf, this star would have an orbital period of around 250,000 years, if it is part of the stellar system.<ref name="kalerrigel"/>


Another spectroscopic companion to Rigel has been reported on the basis of [[radial velocity]] variations, and even an orbit calculated, but it is thought that the star does not exist and the pulsations are intrinsic to Rigel itself.<ref name=sb9/>
Another spectroscopic companion to Rigel has been reported on the basis of [[radial velocity]] variations, and even an orbit calculated, but it is thought that the star does not exist and the pulsations are intrinsic to Rigel itself.<ref name=sb9/>
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== Physical characteristics ==
== Physical characteristics ==
[[File:Hertzsprung-Russel StarData.png|thumb|left|Rigel's place at top center on the [[Hertzsprung-Russell diagram]]]]
[[File:Hertzsprung-Russel StarData.png|thumb|left|Rigel's place at top center on the [[Hertzsprung-Russell diagram]]]]
Rigel is an intrinsically highly luminous star.<ref name=burnham/><ref name="schaaf"/> Using the Hipparcos distance of {{val|264|u=pc}}, the luminosity of Rigel is estimated to be 120,000 times that of the Sun.<ref name=apj2012_747_108/> Its surface temperature is determined from the spectrum and colour and is around 12,100&nbsp;K. The [[interferometer]]-measured [[angular diameter]] of this star, after correction for [[limb darkening]], is {{val|2.75|0.01|u=[[milliarcsecond|mas]]}}.<ref name=auf/> At its estimated distance, this yields a size of about 78.9 times the [[Solar radius|radius of the Sun]] ({{solar radius}}).<ref name=apj2012_747_108/>


Determination of most the physical characteristics of Rigel and other blue supergiant stars are difficult due to their rarity and their poorly known distances from the Sun. As such, much of our knowledge about their characteristics are based on theoretical [[stellar evolution]] models with all parameters having a high degree of uncertainty.
Assuming a distance of {{convert|360|±|40|pc|ly|abbr=off|order=flip}}, Rigel is estimated to be around 218,000 times as luminous as the Sun and to have a radius of {{solar radius|{{val|109|12}}}}. Comparison to evolutionary tracks gives a mass of {{solar mass|{{val|21|3}}}}, while modelling to match the spectrum gives a mass of {{solar mass|{{val|24|8}}}}.<ref name=aaa445_3_1099/>


Although Rigel appears as the most luminous star within 1,000 light-years of the Sun<ref name=burnham/><ref name="schaaf"/>, knowledge about its true energy output remains poorly known. For example, using the Hipparcos distance of {{val|264|u=pc}}, finds the estimated relative luminosity for Rigel is about 120,000 times that of the Sun<ref name=apj2012_747_108/>, but another recently published distance of {{convert|360|±|40|pc|ly|abbr=off} suggests an even higher luminosity of 218,000 times that of the Sun. 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 estimates using historical photometry suggests luminosities as low as {{val|61515|11486|fmt=commas}}.<ref name=baines/>
A 2018 study using the [[Navy Precision Optical Interferometer]] measured the angular diameter of {{val|2.606|0.009|ul=mas}}, yielding the radius as {{solar radius|{{val|74.1|+6.1|-7.3}}}}. Fitting to the [[spectral energy distribution]] (SED) of Rigel, using historical photometry and assuming a distance of {{val|264|u=pc}}, gives a luminosity {{val|61515|11486|fmt=commas}} times that of the Sun.<ref name=baines/>


A 2018 study using the [[Navy Precision Optical Interferometer]] measured the [[angular diameter]] as {{val|2.606|0.009|ul=mas}}, yielding the radius as {{solar radius|{{val|74.1|+6.1|-7.3}}}}. After correcting for [[limb darkening]], this increases to {{val|2.75|0.01|u=[[milliarcsecond|mas]]}}<ref name=auf/>, yielding a true size of about 78.9 times the [[Solar radius|radius of the Sun]] ({{solar radius}})<ref name=apj2012_747_108/> whose error depends on the adopted distance. Assuming distance is {{convert|360|±|40|pc|ly|abbr=off}}, a theoretical solar radius of {{solar radius|{{val|109|12}}}} is possible.
Models of Rigel's atmosphere based on its spectrum give a luminosity is somewhere between {{solar luminosity|83,000}} and {{solar luminosity|363,000}}, respectively based on the Hipparcos distance of {{convert|240|pc|ly|abbr=off|order=flip}} and an Orion OB1 association distance of {{convert|500|pc|ly|abbr=off|order=flip}}.<ref name=markova/>


Rigel is a [[blue supergiant]] that has exhausted burning the hydrogen fuel in its core and left the main sequence, expanded, and brightened as it progresses across the [[Hertzsprung–Russell diagram]]. Puzzlingly, the pulsation properties of this star suggest it passed through the [[red supergiant]] phase, whereas the surface abundances indicate it evolved directly to a blue supergiant.<ref name=saio/> Przybilla estimated that it has lost around 3 solar masses since beginning life as a star of {{val|24|3}} solar masses 7 to 9 million years ago.<ref name=aaa445_3_1099/> It is expected to eventually end its stellar life by exploding as a [[type II supernova]] from a red supergiant, in the process flinging out material that will serve to seed future generations of stars.<ref name=apj2012_749_74/> It is one of the closest known potential supernova progenitors to Earth,<ref name=apj2012_747_108/> and would be expected to have an apparent magnitude of around {{val|-11}} at its peak.<ref name=guinan/>
Comparison of various evolutionary tracks gives a mass of {{solar mass|{{val|21|3}}}}, while theoretical modelling matching the spectral type gives a mass of {{solar mass|{{val|24|8}}}}.<ref name=aaa445_3_1099/> Age is estimated as {{val|8|1}}<ref name=aaa445_3_1099/> million years. Surface temperature has been determined from the spectral type and colour and is around 12,100&nbsp;K.<ref name=przybilla/>
Rigel is a [[blue supergiant]] that has almost exhausted burning the hydrogen fuel in its core and left the main sequence, expanded, and brightened as it progresses across the [[Hertzsprung–Russell diagram]]. Puzzlingly, the pulsation properties of this star suggest it passed through the [[red supergiant]] phase, whereas the surface abundances indicate it evolved directly to a blue supergiant.<ref name=saio/> Przybilla estimated that it has lost around 3 solar masses since beginning life as a star of {{val|24|3}} solar masses 7 to 9 million years ago.<ref name=aaa445_3_1099/> It is expected to eventually end its stellar life by exploding as a [[type II supernova]] from a red supergiant, in the process flinging out material that will serve to seed future generations of stars.<ref name=apj2012_749_74/> It is one of the closest known potential supernova progenitors to Earth,<ref name=apj2012_747_108/> and would be expected to have an apparent magnitude of around {{val|-11}} at its peak.<ref name=guinan/>


Rigel's variability is complex and is caused by [[stellar pulsations]] similar to those of [[Deneb]], the prototype of the class of Alpha Cygni pulsating stars. The radial velocity variations of Rigel prove 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/> While its pulsations are powered by the nuclear reactions in a hydrogen-burning shell that is at least partially non-convective, the star also [[Triple-alpha process|burns helium]] in its core.<ref name=apj2012_749_74 />
Rigel's variability is complex and is caused by [[stellar pulsations]] similar to those of [[Deneb]], the prototype of the class of Alpha Cygni pulsating stars. The radial velocity variations of Rigel prove 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/> While its pulsations are powered by the nuclear reactions in a hydrogen-burning shell that is at least partially non-convective, the star also [[Triple-alpha process|burns helium]] in its core.<ref name=apj2012_749_74 />

Revision as of 02:29, 22 March 2019

For other uses, see Rigel (disambiguation).
Rigel
Map of the constellation Orion
Rigel in the constellation Orion (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Orion
Pronunciation /ˈraɪdʒəl/ or /-ɡəl/[1]
A
Right ascension 05h 14m 32.27210s[2]
Declination −08° 12′ 05.8981″[2]
Apparent magnitude (V) 0.13[3] (0.05 - 0.18[4])
BC
Right ascension 05h 14m 32.049s[5]
Declination −08° 12′ 14.78″[5]
Apparent magnitude (V) 6.67[6] (7.6/7.6[7])
Characteristics
A
Evolutionary stage Blue supergiant
Spectral type B8 Ia[8]
U−B color index −0.66[9]
B−V color index −0.03[9]
Variable type Alpha Cygni[10]
BC
Evolutionary stage Main sequence
Spectral type B9V + B9V[7]
Astrometry
Radial velocity (Rv)17.8±0.4[11] km/s
Proper motion (μ) RA: +1.31[2] mas/yr
Dec.: +0.50[2] mas/yr
Parallax (π)3.78 ± 0.34 mas[2]
Distance860 ± 80 ly
(260 ± 20 pc)
Absolute magnitude (MV)–7.84[12]
Orbit[6]
PrimaryBa
CompanionBb
Period (P)9.860 days
Eccentricity (e)0.1
Semi-amplitude (K1)
(primary)		25.0 km/s
Semi-amplitude (K2)
(secondary)		32.6 km/s
Orbit[7]
PrimaryB
CompanionC
Period (P)63 yr
Details
A
Mass21±3[13] M☉
Radius78.9±7.4[14] R☉
Luminosity (bolometric)1.20+0.25
−0.21×105[14] L☉
Surface gravity (log g)1.75±0.10[15] cgs
Temperature12100±150[15] K
Metallicity [Fe/H]−0.06±0.10[8] dex
Rotational velocity (v sin i)25±3[15] km/s
Age8±1[8] Myr
Ba
Mass3.84[7] M☉
Bb
Mass2.94[7] M☉
C
Mass3.84[7] M☉
Other designations
β Orionis, ADS 3823, STF 668, H II 33, CCDM J05145-0812, WDS J05145-0812[16]
A: Rigel, Algebar, Elgebar, 19 Orionis, HD 34085, HR 1713, HIP 24436, SAO 131907, BD-08°1063, FK5 194
B: Rigel B, GCRV 3111, STF 688B, BU 555B
Database references
SIMBADdata

Rigel (/ˈraɪdʒəl, -ɡəl/), also designated β Orionis (Latinized to Beta Orionis, abbreviated Beta Ori, β Ori), is a variable star. It is, on average, the seventh-brightest star in the night sky and the brightest star in the constellation of Orion—though occasionally it is outshone within the constellation by Betelgeuse, another variable star. The apparent magnitude of Rigel varies irregularly between +0.05 and +0.18.

Although appearing as a single star to the naked eye, Rigel is actually a multiple star system. The name Rigel strictly refers to the brightest component of this system. It is a massive blue-white supergiant estimated to be anywhere from 61,500 to 363,000 times as luminous as the Sun, depending on the method used to calculate its properties and assumptions about its distance, thought to be about 260 parsecs (860 ly). Rigel has started to exhaust hydrogen in its core, causing the star to expand; its radius is over 70 times that of the Sun. Pulsations cause Rigel's small intrinsic brightness variation; it is classified as an Alpha Cygni variable.

Rigel's brightest companion is itself a likely triple star system, separated from Rigel by 9.5″. Often referred to as Rigel B, it has a combined apparent magnitude of 6.7 but is still over 400 times fainter than the primary star and visible only with a telescope. Rigel B is a spectroscopic binary composed of the components Ba and Bb. It also has a very close visual companion, component C, of almost equal brightness to B.

Nomenclature

The name Rigel was likely first recorded in the Alfonsine Tables of 1521. It is derived from the Arabic name Rijl Jauzah al Yusrā, "the left leg (foot) of Jauzah" (i.e. rijl meaning "leg, foot"),[17] which can be traced to the 10th century.[18] "Jauzah" was a proper name of the Orion figure, an alternative Arabic name was رجل الجبار riǧl al-ǧabbār, "the foot of the great one", which is the source of the rarely used variant names Algebar or Elgebar. The Alphonsine Tables saw its name split into "Rigel" and "Algebar", with the note, et dicitur Algebar. Nominatur etiam Rigel.[19] Alternate spellings from the 17th century include Regel by Italian astronomer Giovanni Battista Riccioli, Riglon by German astronomer Wilhelm Schickard, and Rigel Algeuze or Algibbar by English scholar Edmund Chilmead.[17] In 2016, the International Astronomical Union officially recognized Rigel for β Orionis A, the blue supergiant component visible to the naked eye.[20]

β Orionis (Latinized to Beta Orionis) is the star's Bayer designation, although it is usually the brightest star in Orion. Astronomer James B. Kaler has speculated that perhaps Rigel was designated by Bayer during a rare period where it was outshone by the variable star Betelgeuse, resulting in the latter star being designated alpha and Rigel designated beta.[21] Rigel is included in the General Catalogue of Variable Stars, but since it already has a Bayer designation, β Orionis, it has no separate variable star designation.[22]

Observation

Rigel is the seventh-brightest star in the celestial sphere excluding the Sun. It is usually fainter than Capella,[23] although both are slightly variable in brightness. Rigel is an irregular pulsating variable with a range in apparent magnitude from 0.05 to 0.18.[4] Although Rigel has the Bayer designation "beta", it is almost always brighter than Alpha Orionis (Betelgeuse).[23] Since 1943, the spectrum of this star has served as a spectral reference for class B8Ia, for use as a comparison when classifying the spectra of other stars.[24][25] Rigel appears slightly blue-white, almost white, and has a (B–V) color index of −0.06.[26]

Culminating at midnight on 12 December, and at 9 pm on 24 January, Rigel is visible in winter evenings in the northern hemisphere and summer in the southern.[23] In the southern hemisphere, Rigel is the first bright star of Orion visible as the constellation rises.[27] The star forms a vertex of the "Winter Hexagon", an asterism that includes Aldebaran, Capella, Pollux, Procyon, and Sirius. This formation is visible from most locations on Earth and is prominent in the night sky from December through March.[28] Rigel is a recognised equatorial navigation star, being easily located and readily visible in all the world's oceans (the exception is the area within 8° of the North Pole).[29]

Spectroscopy

Orion with Rigel at bottom right, at optical wavelengths plus Hα to emphasize gas clouds

The general spectral type of Rigel as B8 is well-established and it has been used as a defining point of the spectral classification sequence for supergiants.[30][31] The overall spectrum is typical for a late B class star, with strong absorption lines of the hydrogen Balmer series together with neutral helium lines and some of heavier elements such as oxygen, calcium, and magnesium.[32] The luminosity class for B8 stars is determined from the strength and narrowness of the hydrogen spectral lines, and Rigel is assigned to the bright supergiant class Ia.[24]

As early as 1888, the radial velocity of Rigel, as determined from the Doppler shifts of its spectral lines, was seen to vary. This was confirmed and interpreted as a spectroscopic companion with a period of about 22 days.[33] The radial velocity has since been measured to vary by about 10 km/s around a mean of 21.5 km/s.[34]

In 1933, the Hα spectral line was seen to be unusually weak and shifted 0.1 nm towards shorter wavelengths, while there was a narrow emission spike about 1.5 nm to the long wavelength side of the main absorption line.[35] This is now known as a P Cygni profile after a star that shows this feature strongly in its spectrum. It is associated with strong mass loss where there is simultaneously emission from dense wind close to the star and absorption from circumstellar material expanding away from the star.[35]

The unusual Hα line profile has since been observed to vary unpredictably: around a third of the time it is a normal absorption line; about a quarter of the time it is a double-peaked line, that is an absorption line with an emission core or an emission line with an absorption core; about a quarter of the time it has a P Cygni profile; most of the rest of the time the line has an inverse P Cygni profile, where the emission component is on the short wavelength side of the line; rarely there is a pure emission Hα line.[34] The line profile changes are interpreted as variations in the quantity and velocity of material being expelled from the star. Occasional very high velocity outflows have been observed, and, more rarely, infalling material. The overall picture is one of large looping structures arising from the photosphere and driven by magnetic fields.[36]

The variations in the spectrum have been reflected in published spectral classes, such as B8 Ia, B8 Iab, and B8 Iae.[13][37]

Variability

Rigel has been known to vary in brightness since at least 1930, although the exact range and type of variability was unclear. Published results showed variations of less than 0.1 magnitudes with no obvious period. Observations over 18 nights in 1984 showed variations at red, blue, and yellow wavelengths of up to 0.13 magnitudes on timescales of a few hours to several days, but again no clear period. The colour index also varied but in general was not strongly correlated with the brightness variations.[38]

From an analysis of Hipparcos satellite photometry, Rigel was identified as belonging to the Alpha Cygni class of variable star in 1998,[39] which are defined as "non-radially pulsating supergiants of the Bep–AepIa spectral types".[40] (The 'e' indicates it displays emission lines in the spectrum, while the 'p' means it has an unspecified spectral peculiarity.) It was added to the General Catalogue of Variable Stars in the following year in the 74th namelist of variable stars.[41] The Hipparcos photometry showed variations with a photographic amplitude of 0.039 magnitudes and a possible period of 2.075 days.[42]

Rigel was observed with the Canadian MOST satellite for nearly 28 days in 2009. The light variations in this supergiant star were at the milli-magnitude level. The gradual changes in the flux highlights the presence of long-period pulsation modes in the star.[14]

Mass loss

From spectroscopic observations of the variable Hα spectral line, the mass loss from Rigel is estimated to be (1.5±0.4)×10−7 solar masses per year (M☉/yr), around ten million times more than the mass loss from the Sun.[43] More detailed optical and K band infrared spectroscopic observations, together with VLTI interferometry, were taken from 2006 to 2010. Analysis of the Hα and Hγ line profiles, and measurement of the regions producing the lines, show that the stellar wind varies greatly in structure and strength. Loop and arm structures were also detected within the wind. Calculations of mass loss from the Hγ line give (9.4±0.9)×10−7 M☉/yr in 2006-7 and (7.6±1.1)×10−7 M☉/yr in 2009-10. Calculations using the Hα line give lower results, around 1.5×10−7 M☉/yr. The terminal wind velocity is 300 km·s−1.[44]

Distance

Rigel and reflection nebula IC 2118 in Eridanus. Rigel B is not visible in the glare of the main star.

An accurate distance for Rigel is difficult to independently determine due to the star's brightness and small measured parallax. Other indirect distant methods have been recently employed. For example, Rigel is believed to be moving through a region of nebulosity whose brightness lights up several dust clouds in its vicinity. Most notably of these is the 5°[45]–long IC 2118 (the Witch Head Nebula),[46] located at an angular separation of 2.5° from the star, [45] and are thought to be about 40 light-years (12 parsecs) away.[21] Measures of other nebula embedded stars estimate Rigel's distance to be 949 ± 7 light-years (291 ± 2 parsecs).[47]

Rigel has been classified as an outlying member of the Orion OB1 Association, which is located at a distance of up to 1,600 light-years (500 parsecs) from Earth. It has also been listed as a member of the poorly-defined Taurus-Orion R1 Association, somewhat closer at 1,200 light-years (360 parsecs).[48][49] Rigel is thought to be considerably closer than most of the members of Orion OB1 and the Orion Nebula. Betelgeuse and Saiph lie at a similar distance as Rigel, although Betelgeuse is a runaway star with a complex history and might have originally formed in the main body of the association.[37]

The revised 2007 Hipparcos reduction of Rigel's parallax gives a distance of 863 light-years (265 parsecs), with a margin of error of about 9%.[2] A companion star to Rigel, usually considered to be physically associated and at the same distance, has a Gaia Data Release 2 parallax of 2.9186±0.0761 mas, implying a distance around 1,100 light-years (340 parsecs). However, the measurements for this object show a number of features, suggesting they may be unreliable, possibly because it is a close double star.[50]

Stellar system

Rigel
Separation=9.5″
Period=24,000 y
Ba
Separation=0.58 mas
Period=9.860 d
Bb
Separation=0.1″
Period=63 y
C

Hierarchical scheme for Rigel's components[7]

Rigel forms a multiple star system with up to five or six components. The blue supergiant primary has a visual companion which is itself a likely a close triple star, plus a more distant visual companion that may also form part of the multiple star system.

William Herschel discovered Rigel to be a visual double star on 1 October 1781, and it was catalogued as H II 33 (or H 2 33[51]).[52] Friedrich Georg Wilhelm von Struve first measured the relative position of the companion in 1822, cataloging the visual pair as Σ 668.[53] The secondary star can be referred to as Rigel B or β Ori B. The angular separation of β Ori B from the primary star is 9.5 arc seconds to its south along position angle 204°.[51][54] Although not particularly faint at visual magnitude 6.7, the overall difference in brightness from the primary (about 6.6 magnitudes or 440 times fainter) makes it a challenging target for telescope apertures smaller than 15 cm (6 in).[6]

At Rigel's estimated distance, β Ori B's projected separation from its primary is over 2,200 AU. Since its discovery, there has been no sign of orbital motion, although both stars share similar common proper motion.[55][46] The pair would have a minimum orbital period of around 18,000 years.[7] Gaia Data Release 2 (DR2) contains a somewhat unreliable parallax for β Ori B, placing it at about 1,100 light-years (340 parsecs), further away than the Hipparcos distance for Rigel, but similar to the Taurus-Orion R1 association. There is no parallax for Rigel in Gaia DR2. The Gaia DR2 proper motions for β Ori B and the Hipparcos proper motions for Rigel are both small, although not quite the same.[50]

In 1871, Sherburne Wesley Burnham suspected β Ori B to be double, and in 1878, he resolved it into two nearly equal components.[56] Their measured separation varies from less than 0.1" to nearly 0.2". In 2009, speckle interferometry showed two almost identical components separated by 0.124".[57] The companion is designated as component C (β Ori C).[clarification needed] Both stars have apparent visual magnitudes of 7.6. Their derived orbital period is 63 years.[7]

β Ori B appears to be a double-lined spectroscopic binary system, which indicates that the individual absorption lines of both components is visible in the spectrum. It consists of two main sequence stars that orbit each other every 9.86 days. These two stars do not seem to correspond to the visual binary components B and C, so the BC sub-system might be a triple, although the actual arrangement is unclear.[55][6]

In 1878, Burnham found a further nearby 15th magnitude star, catalogued as component D (β Ori D)[clarification needed] , whose 2017 separation from Rigel was 44.5″ almost due north at position angle of 1°,[51] although it is unclear whether it is physically related or a coincidental alignment. Gaia DR2 finds it to be a 12th magnitude sunlike star at approximately the same distance as Rigel.[58] Most likely to be an orange dwarf, this star would have an orbital period of around 250,000 years, if it is part of the stellar system.[21]

Another spectroscopic companion to Rigel has been reported on the basis of radial velocity variations, and even an orbit calculated, but it is thought that the star does not exist and the pulsations are intrinsic to Rigel itself.[55]

Physical characteristics

File:Hertzsprung-Russel StarData.png
Rigel's place at top center on the Hertzsprung-Russell diagram

Determination of most the physical characteristics of Rigel and other blue supergiant stars are difficult due to their rarity and their poorly known distances from the Sun. As such, much of our knowledge about their characteristics are based on theoretical stellar evolution models with all parameters having a high degree of uncertainty.

Although Rigel appears as the most luminous star within 1,000 light-years of the Sun[59][23], knowledge about its true energy output remains poorly known. For example, using the Hipparcos distance of 264 pc, finds the estimated relative luminosity for Rigel is about 120,000 times that of the Sun[14], but another recently published distance of {{convert|360|±|40|pc|ly|abbr=off} suggests an even higher luminosity of 218,000 times that of the Sun. Other calculations based on theoretical stellar evolutionary models of Rigel's atmosphere give luminosities anywhere between 83,000 L☉ and 363,000 L☉[48], while estimates using historical photometry suggests luminosities as low as 61,515±11,486.[60]

A 2018 study using the Navy Precision Optical Interferometer measured the angular diameter as 2.606±0.009 mas, yielding the radius as 74.1+6.1
−7.3 R☉. After correcting for limb darkening, this increases to 2.75±0.01 mas[61], yielding a true size of about 78.9 times the radius of the Sun (R☉)[14] whose error depends on the adopted distance. Assuming distance is 360 ± 40 parsecs (1,170 ± 130 light-years), a theoretical solar radius of 109±12 R☉ is possible.

Comparison of various evolutionary tracks gives a mass of 21±3 M☉, while theoretical modelling matching the spectral type gives a mass of 24±8 M☉.[8] Age is estimated as 8±1[8] million years. Surface temperature has been determined from the spectral type and colour and is around 12,100 K.[15]

Rigel is a blue supergiant that has almost exhausted burning the hydrogen fuel in its core and left the main sequence, expanded, and brightened as it progresses across the Hertzsprung–Russell diagram. Puzzlingly, the pulsation properties of this star suggest it passed through the red supergiant phase, whereas the surface abundances indicate it evolved directly to a blue supergiant.[62] Przybilla estimated that it has lost around 3 solar masses since beginning life as a star of 24±3 solar masses 7 to 9 million years ago.[8] It is expected to eventually end its stellar life by exploding as a type II supernova from a red supergiant, in the process flinging out material that will serve to seed future generations of stars.[10] It is one of the closest known potential supernova progenitors to Earth,[14] and would be expected to have an apparent magnitude of around −11 at its peak.[4]

Rigel's variability is complex and is caused by stellar pulsations similar to those of Deneb, the prototype of the class of Alpha Cygni pulsating stars. The radial velocity variations of Rigel prove that it simultaneously oscillates in at least 19 non-radial modes with periods ranging from about 1.2 to 74 days.[14] While its pulsations are powered by the nuclear reactions in a hydrogen-burning shell that is at least partially non-convective, the star also burns helium in its core.[10]

Visual double star β Ori B appears to be a close triple star system (Rigel Ba, Bb, and C), but due to their proximity, little is known about their individual intrinsic properties. All seem to be near equally hot B-type main-sequence stars that are 3 to 4 times as massive as the Sun.[7]

Etymology and cultural significance

In the constellation of Orion, Rigel represents Orion's knee or (as its name suggests) his foot; with the nearby star Beta Eridani marking Orion's footstool.[23] Rigel is presumably the star known as "Aurvandil's toe" in Norse mythology.[63] In the Caribbean, Rigel represented the severed leg of the folkloric figure Trois Rois, himself represented by the three stars of Orion's Belt. The leg had been severed with a cutlass by the maiden Bįhi (Sirius).[64] The Lacandon people of southern Mexico knew it as tunsel ("little woodpecker").[65]

Rigel was known as Yerrerdet-kurrk to the Wotjobaluk koori of southeastern Australia, and held to be the mother-in-law of Totyerguil (Altair). The distance between them signified the taboo preventing a man from approaching his mother-in-law.[66] The indigenous Boorong people of northwestern Victoria named Rigel as Collowgullouric Warepil.[67] The Wardaman people of northern Australia know Rigel as the Red Kangaroo Leader Unumburrgu and chief conductor of ceremonies in a songline when Orion is high in the sky. Eridanus, the river, marks a line of stars in the sky leading to it, and the other stars of Orion are his ceremonial tools and entourage. Betelgeuse is Ya-jungin "Owl Eyes Flicking", watching the ceremonies.[68] The Māori people of New Zealand named Rigel as Puanga; this was said to be a daughter of Rehua (Antares), the chief of all stars.[69] Its heliacal rising also presaged the appearance of Matariki (the Pleiades) in the dawn sky which marked the Māori New Year in late May or early June. The Moriori people of the Chatham Islands, as well as some Maori groups in New Zealand, marked the start of their New Year with Rigel rather than the Pleiades.[70] Puaka was a local variant used in the South Island.[71] In Japan, the Minamoto or Genji clan chose Rigel and its white color as its symbol, calling the star Genji-boshi (源氏星), while the Taira or Heike clan adopted Betelgeuse and its red color. The two powerful families fought the Genpei War; the stars were seen as facing each other off and only kept apart by Orion's Belt.[72][73][74] Rigel was also known as Gin-waki, (銀脇), "the Silver (Star) beside (Mitsu-boshi)".

In modern culture

Rigel and escort under attack

The MS Rigel was originally a Norwegian ship, built in Copenhagen in 1924. It was requisitioned by the Germans during the World War II and sunk in 1944 while being used to transport prisoners of war.[75] Two US Navy ships have borne the name USS Rigel.

The SSM-N-6 Rigel was a cruise missile program for the US Navy that was cancelled in 1953 before reaching deployment.[76]

The Rigel Skerries are a chain of small islands in Antarctica, renamed after originally being called Utskjera. They were given their current name as Rigel was used as an astrofix.[77] Mount Rigel, also in Antarctica, is also named after the star.[78]

The name Rigel, or reference to the star itself, occurs frequently in fictional works.

References

  1. ^ "Define Rigel at Dictionary.com". Retrieved 6 February 2012.
  2. ^ a b c d e f van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  3. ^ Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  4. ^ a b c Guinan, E. F.; Eaton, J. A.; Wasatonic, R.; Stewart, H.; Engle, S. G.; McCook, G. P. (2010). "Times-Series Photometry & Spectroscopy of the Bright Blue Supergiant Rigel: Probing the Atmosphere and Interior of a SN II Progenitor". Proceedings of the International Astronomical Union. 5: 359. Bibcode:2010HiA....15..359G. doi:10.1017/S1743921310009798.
  5. ^ a b DENIS Consortium (2005). "VizieR Online Data Catalog: The DENIS database (DENIS Consortium, 2005)". VizieR On-line Data Catalog: B/denis. Originally Published In: 2005yCat.2263....0T. 1. Bibcode:2005yCat....102002D.
  6. ^ a b c d Sanford, Roscoe F. (1942). "The Spectrographic Orbit of the Companion to Rigel". Astrophysical Journal. 95: 421. Bibcode:1942ApJ....95..421S. doi:10.1086/144412.
  7. ^ a b c d e f g h i j Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". Astronomy & Astrophysics Supplement Series. 124: 75–84. Bibcode:1997A&AS..124...75T. doi:10.1051/aas:1997181.
  8. ^ a b c d e f Przybilla, N.; et al. (January 2006). "Quantitative spectroscopy of BA-type supergiants". Astronomy and Astrophysics. 445 (3): 1099–1126. arXiv:astro-ph/0509669. Bibcode:2006A&A...445.1099P. doi:10.1051/0004-6361:20053832.
  9. ^ a b Nicolet, B. (1978). "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System". Astronomy and Astrophysics Supplement Series. 34: 1–49. Bibcode:1978A&AS...34....1N.
  10. ^ a b c Moravveji, Ehsan; Moya, Andres; Guinan, Edward F. (April 2012). "Asteroseismology of the nearby SN-II Progenitor: Rigel. Part II. ε-mechanism Triggering Gravity-mode Pulsations?". The Astrophysical Journal. 749 (1): 74–84. arXiv:1202.1836. Bibcode:2012ApJ...749...74M. doi:10.1088/0004-637X/749/1/74.
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External links

source: https://en.wikipedia.org/w/index.php?title=Rigel&diff=888898209&oldid=888853879

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