Editing Regulus (section)

{{short description|Brightest star in the constellation Leo}}
{{about|the star||Regulus (disambiguation)}}
{{Starbox begin}}
{{Starbox image
 | image=
   {{Location mark
     | image=Leo constellation map.svg
     | float=center | width=250 | position=right
     | mark=Red circle.svg | mark_width=10 | mark_link=Alpha Leo
     | x%=76.8 | y%=77.7
   }}
 | caption=Location of Regulus (circled)
}}
{{Starbox observe 2s
 | pronounce    = {{IPAc-en|UK|'|r|E|g|ˌ|j|u|l|ʊ|s}} {{IPAc-en|US|'|r|E|g|ˌ|j|ʊ|l|ʊ|s|,}}<ref>{{OED|regulus}}</ref>
 | epoch        = J2000
 | constell     = [[Leo (constellation)|Leo]]
 | component1   = Regulus A
 | ra1          = {{RA|10|08|22.311}}<ref name="van Leeuwen2007"/>
 | dec1         = {{DEC|+11|58|01.95}}<ref name="van Leeuwen2007"/>
 | appmag_v1    = 1.40<ref name="van Belle2009"/>
 | component2   = Regulus BC
 | ra2          = {{RA|10|08|12.8}}<ref name=tycho2/>
 | dec2         = {{DEC|+11|59|49}}<ref name=tycho2/>
 | appmag_v2    = 8.13<ref name=tokovinin/>/13.50<ref name=tokovinin/>
}}
{{Starbox character
 | component1   = Regulus A
 | type         = [[Subgiant]]
 | class        = B8&nbsp;IVn<ref name="van Belle2009"/>
 | b-v          = –0.11<ref name=ducati/>
 | u-b          = –0.36<ref name=ducati/>
 | variable     = Suspected<ref name=gcvs/>
 | component2   = Regulus BC
 | type2        = [[Main sequence]]
 | class2       = K2&nbsp;V<ref name=gies/> + M4&nbsp;V<ref name=gies/>
 | b-v2         = +0.86<ref name=ducati/>
 | u-b2         = +0.51<ref name=ducati/>
}}
{{Starbox astrometry
 | component1   = A
 | radial_v     = {{val|4.39|0.09}}<ref name="Gies2020"/>
 | prop_mo_ra   = {{val|−248.73|0.35}}<ref name="van Leeuwen2007"/>
 | prop_mo_dec  = {{val|5.59|0.21}}<ref name="van Leeuwen2007"/>
 | parallax     = 41.13
 | p_error      = 0.35
 | parallax_footnote = <ref name="van Leeuwen2007"/>
 | absmag_v     = –0.57<ref name=Anderson2012/>
 | component2   = BC
 | radial_v2    = +6.72<ref name=edr3/>
 | prop_mo_ra2  = {{val|−254.399|0.028}}<ref name=edr3/>
 | prop_mo_dec2 = {{val|8.127|0.027}}<ref name=edr3/>
 | parallax2    = 41.2745
 | p_error2     = 0.0270
 | parallax_footnote2 = <ref name=edr3/>
 | absmag_v2    = 6.20/11.56<ref name=johnson1983/>
}}
{{Starbox orbit
 | reference    = <ref name="Gies2020"/>
 | primary      = α Leo Aa (HD 87901 A)
 | name         = α Leo Ab (HD 87901 B)
 | period_unitless = {{val|40.102|0.002|u=days}}
 | axis_unitless = {{val|6.00|0.17|ul=Solar radius|s=&nbsp;projected}}
 | eccentricity = 0 (assumed)
 | k1           = {{val|7.58|0.12}}
 | k2           = <!-- Velocity semi-amplitude (secondary in SB2), in km/s -->
}}
{{Starbox detail
 | component1   = A
 | age_gyr      = ≳1<ref name="rappaport2009"/>
 | metal_fe     = +0.21<ref name=baines/>
 | mass         = {{val|4.15|0.06}}<ref name=che/>
 | radius       = {{val|4.21|0.07|0.06}} (equatorial), {{val|3.22|0.05|0.06}} (polar)<ref name=che/>
 | gravity      = {{val|3.54|0.09}}<ref name=aj129_3_1642/>
 | rotational_velocity = {{val|318|8}}<ref name="Cotton2017"/>
 | rotation     = 15.9 hours<ref name="apj628"/>
 | luminosity   = {{val|341|27|28}}<ref name=che/>
 | temperature  = 11,010 (equatorial), 14,520 (polar)<ref name=che/>
 | component2 = Ab
 | mass2 = {{val|0.31|0.10}}<ref name="Gies2020"/>
 | temperature2 = {{val|20000|4000|fmt=commas}}<ref name="Gies2020"/>
 | radius2 = {{val|0.061|0.011}}<ref name="Gies2020"/>
}}
{{Starbox detail
 | no_heading=y
 | component1   = B
 | mass         = 0.8<ref name=martin/>
 | radius       = 0.83<ref name=johnson1983/>
 | luminosity   = 0.50<ref name=martin/>
 | temperature  = 4,885<ref name=martin/>
 | gravity      = 4.4<ref name=martin/>
 | metal_fe     = −0.21<ref name=casagrande2011/>
 | component2   = C
 | mass2        = 0.3<ref name=tokovinin/>
 | radius2      = 0.37<ref name=johnson1983/>
 | luminosity2  =
 | temperature2 = 3,242<ref name=johnson1983/>
 | gravity2     = 
}}
{{Starbox catalog
 | names      = {{odlist | name=α&nbsp;Leonis <!--Cor Leonis, Lion’s Heart, Kalb al Asad, Kabeleced, --> | F=32&nbsp;Leonis | GJ=9316 | HR=3982 | ADS=7654 | WDS=J10084+1158 }}
 | component1 = α Leo A
 | names1     = {{odlist | BD=+12°2149 | HD=87901 | HIP=49669 | LTT=12716 | SAO=98967 | FK5=380 | GCTP=2384.00 }}
 | component2 = α Leo B/C
 | names2     = {{odlist | BD=+12°2147 | HD=87884 | LTT=12714 | SAO=98966 }}
}}
{{Starbox reference
 | Simbad=HD+87901|sn=Regulus
 | Simbad2=HD+87884|sn2=BC
}}
{{Starbox end}}

'''Regulus''' is the brightest object in the [[constellation]] [[Leo (constellation)|Leo]] and one of the [[List of brightest stars|brightest stars]] in the [[night sky]]. It has the [[Bayer designation]] designated '''α Leonis''', which is [[Latinisation of names|Latinized]] to '''Alpha Leonis''', and abbreviated '''Alpha Leo''' or '''α Leo'''. Regulus appears singular, but is actually a quadruple [[star system]] composed of four stars that are organized into two pairs. The [[Binary star#Spectroscopic binaries|spectroscopic binary]] Regulus A consists of a blue-white [[main-sequence]] star and its companion, a pre-[[white dwarf]]. The system lies approximately 79 [[light year]]s from the [[Solar System]].

HD 87884 is separated from Regulus by {{val|176|ul="}} and is itself a close pair. Regulus, along with five slightly dimmer stars ([[Zeta Leonis]], [[Mu Leonis]], [[Gamma Leonis]], [[Epsilon Leonis]], and [[Eta Leonis]]) have collectively been called 'the Sickle', which is an [[Asterism (astronomy)|asterism]] that marks the head of Leo.