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{{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 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 V<ref name=gies/> + M4 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= 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 Leonis <!--Cor Leonis, Lion’s Heart, Kalb al Asad, Kabeleced, --> | F=32 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. == Nomenclature == ''α Leonis'' (Latinized to ''Alpha Leonis'') is the star system's [[Bayer designation]]. The traditional name ''Rēgulus'' is [[Latin]] for 'prince' or 'little king'. In 2016, the [[International Astronomical Union]] organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN"/> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name="WGSN1"/> included a table of the first two batches of names approved by the WGSN; which included ''Regulus'' for this star. It is now so entered in the IAU Catalog of Star Names.<ref name="IAU-CSN"/> == Observation == [[File:Regulus 1.JPG|thumb|Regulus through Celestron CGEM DX 1100 @ F6.3, Canon T3i, Televue 4X Powermate, ISO 800, 30 sec exposure|alt=|left]] The Regulus system as a whole is the twenty-first [[Brightest stars|brightest star]] in the night sky with an [[apparent magnitude]] of +1.35. The light output is dominated by Regulus A. Regulus B, if seen in isolation, would be a binocular object of magnitude +8.1, and its companion, Regulus C, the faintest of the three stars that has been directly observed, would require a substantial telescope to be seen, at magnitude +13.5. Regulus A is itself a spectroscopic binary; the secondary star has not yet been directly observed as it is much fainter than the primary. The BC pair lies at an angular distance of 177 arc-seconds from Regulus A, making them visible in amateur telescopes.<ref name="pugh"/> [[File:MVI 3269-Regulus-1.png|thumb|Regulus as viewed through a 110mm refractor in full daylight.|alt=|left]] Regulus is 0.465 degrees from the [[ecliptic]],<ref name=pratt/> the closest of the bright stars, and is often [[occultation|occulted]] by the [[Moon]]. This occurs in spates every 9.3 years, due to [[lunar precession]]. The last spate was around 2017, with occultations every month from December 2016 till July 2017, each one limited to certain areas on Earth.<ref>See [https://web.archive.org/web/20160309173111/http://www.lunar-occultations.com/iota/bstar/bstar.htm 2016 Bright Star Occultations] and [https://web.archive.org/web/20170307064802/http://www.lunar-occultations.com/iota/bstar/bstar.htm 2017 Bright Star Occultations].</ref> Occultations by [[Mercury (planet)|Mercury]] and [[Venus]] are possible but rare, as are occultations by [[asteroid]]s. Seven other stars which have a [[Bayer designation]] are less than 0.9° from the ecliptic (perfected, mean plane of Earth's orbit and mean apparent path of the Sun) the next brightest of which is [[Delta Geminorum|δ (Delta) Geminorum]], of magnitude +3.53. The last occultation of Regulus by a planet was on July 7, 1959, by Venus.<ref name="planets" /> The next will occur on October 1, 2044, also by Venus. Other planets will not occult Regulus over the next few millennia because of their [[orbital node|node positions]]. An occultation of Regulus by the asteroid [[166 Rhodope]] was filmed in Italy on October 19, 2005. Differential bending of light was measured to be consistent with [[general relativity]].<ref name="rhodope"/> Regulus was occulted by the asteroid [[163 Erigone]] in the early morning of March 20, 2014.<ref name=sigismondi/> The center of the shadow path passed through [[New York (state)|New York]] and [[eastern Ontario]], but no one is known to have seen it, due to cloud cover. The International Occultation Timing Association recorded no observations at all.<ref name=iota/> Although best seen in the evening in the northern hemisphere's late winter and spring, Regulus appears at some time of night throughout the year except for about a month (depending on ability to compensate for the sun's glare, ideally done so in twilight) on either side of August 22–24, when the Sun is too close.<ref name=skymap/> The star can be viewed the whole night, crossing the sky, in late February. Regulus passes through [[Solar and Heliospheric Observatory|SOHO]]'s [[Large Angle and Spectrometric Coronagraph|LASCO]] C3 every August.<ref name="SOHO" /> For Earth observers, the [[heliacal rising]] (pre-sunrise appearance) of Regulus occurs late in the first week of September, or in the second week. Every 8 years, [[Venus]] passes very near the star system around or a few days before the heliacal rising, as on 5 September 2022 (the superior conjunction of Venus happens about two days earlier with each turn of its 8-year cycle, so as this cycle continues Venus will more definitely pass Regulus ''before'' the star's heliacal rising).{{cn|date=September 2022}} ==Stellar system== [[File:LeoCC.jpg|thumb|left|upright|Regulus is the brightest star in the constellation of Leo (right tip, below is bright Jupiter in 2004).]] Regulus is a multiple [[star system]] consisting of at least four stars and a [[substellar object]]. Regulus A is the dominant star, with a binary companion 177" distant that is thought to be physically related. Regulus D is a 12th magnitude companion at 212",<ref name="wds" /> but is an unrelated background object.<ref name="dr2" /> Regulus A is a binary star consisting of a blue-white [[subgiant]] star of spectral type B8, which is orbited by a star of at least 0.3 solar masses, which is probably a [[white dwarf]]. The two stars take approximately 40 days to complete an orbit around their common centre of mass. Given the extremely distorted shape of the primary, the relative orbital motion may be notably altered with respect to the two-body purely [[Keplerian]] scenario because of non-negligible long-term orbital perturbations affecting, for example, its [[orbital period]]. In other words, [[Kepler's third law]], which holds exactly only for two point-like masses, would no longer be valid for the Regulus system. Regulus A was long thought to be fairly young, only 50–100 million years old, calculated by comparing its temperature, luminosity, and mass. The existence of a white dwarf companion would mean that the system is at least 1 billion years old, just to account for the formation of the white dwarf. The discrepancy can be accounted for by a history of mass transfer onto a once-smaller Regulus A.<ref name="rappaport2009" /> The primary of Regulus A has about 4.15 times the [[Sun|Sun's]] mass.<ref name=che/> It is spinning extremely rapidly, with a rotation period of only 15.9 hours (for comparison, the rotation period of the Sun is 25 days<ref>{{Cite web |title=Sun Fact Sheet |url=https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html |access-date=2023-12-15 |website=nssdc.gsfc.nasa.gov}}</ref>), which causes it to have a highly [[oblate spheroid|oblate]] shape.<ref name="apj628"/> This results in so-called [[gravity darkening]]: the photosphere at Regulus' poles is considerably hotter, and five times brighter per unit surface area, than its equatorial region.<ref name="rappaport2009" /> The star's surface at the equator rotates at about 320 kilometres per second (199 miles per second), or 96.5% of its critical angular velocity for break-up. It is emitting [[Polarization (waves)|polarized light]] because of this.<ref name="Cotton2017"/> Regulus BC is 5,000 [[astronomical unit|AU]]<ref name=lindroos/> from Regulus A. A and BC share a [[common proper motion]] and are thought to orbit each other<ref name="tokovinin" /> taking several million years. Designated Regulus B and Regulus C, the pair has [[Henry Draper Catalogue]] number HD 87884. The first is a K2V star, while the second is about M4V.<ref name="apj628" /> The companion pair has an orbital period of about 600 years<ref name="tokovinin" /> with a separation of 2.5" in 1942.<ref name="apj628" /> A far more distant [[brown dwarf]] named SDSS J1007+1930 (full name: SDSS J100711.74+193056.2) may be bound to the Regulus system, since it shares a similar [[proper motion]] and [[radial velocity]] and has a similar [[metallicity|metal abundance]] to Regulus B, which hints for a physical connection between both systems. The estimated distance from Regulus is {{Val|3.9|0.6|0.5|u=[[parsec]]s}} ({{Val|{{convert|3.866|pc|ly|disp=number|sigfig=3}}|{{convert|0.607|pc|ly|disp=number|sigfig=2}}|{{convert|0.473|pc|ly|disp=number|sigfig=2}}|ul=ly}}), and the [[orbital period]] assuming an circular orbit would be around 200 million years, comparable to the Sun's orbital period around the Milky Way ([[galactic year]]). It is estimated to have a mass of roughly {{jupiter mass|60|link=y}} ({{Solar mass|0.06}}),{{Efn|Assuming an age of one billion years. This mass is below the [[hydrogen burning limit]] and make SDSS J100711.74+193056.2 [[substellar object|substellar]], unable to fuse hydrogen and become a dim star.|group=note}} an [[effective temperature]] of {{val|1600|ul=K|fmt=commas}} and a [[spectral type]] L9 or T0, making it a [[L dwarf]] or [[T dwarf]]. In the future it will either be stripped away by stellar encounters because it is so weakly bound to the system, or it was once closer and got ejected by dynamical interactions. The extreme distance makes it uncertain to conclude whether it is gravitationally bound to Regulus.<ref name="Mamajek+Burgasser2024"/> [[File:Regulus in true color.jpg|left|thumb|169x169px|Approximate true-color reconstruction of Regulus based on interferometric imaging.<ref name="che" />]] {|class="wikitable" align=center |+Regulus system !colspan=3| !Separation<br />([[minute and second of arc|arcsec]]) !Projected<br />separation<br />([[astronomical unit|AU]]) !Orbital<br />period ![[stellar classification|Spectral<br />type]] !Mass<br />([[solar mass|M<sub>☉</sub>]]) ![[apparent magnitude|App. mag.]]<br />(V) |- |align=center rowspan=4| Regulus ABC ||align=center rowspan=2 style="background-color: #EEEEEE"|Regulus A<ref group="orbit note" name="orbit">Regulus A and B are separated by 180 arcseconds, resulting in a projected separation of 4400 AU/0.07 light years. The combined binary system may have an approximate orbital period of 130,000 years.</ref> ||align=center style="background-color: #EEEEEE"| Regulus Aa ||align=center rowspan=2 style="background-color: #EEEEEE"| 0.015 ||align=center rowspan=2 style="background-color: #EEEEEE"| 0.356 ||align=center rowspan=2 style="background-color: #EEEEEE"| 40.1 days ||align=center style="background: {{star-color|B}}; | B8 IVn ||align=center| 3.44 ||align=center rowspan=2| 1.4<br />(combined) |- |align=center style="background-color: #EEEEEE"| Regulus Ab ||align=center style="background: {{star-color|D}}; | pre-WD ||align=center| 0.31 |- |align=center rowspan=2 style="background-color: #DDDDDD"| Regulus BC<ref group="orbit note" name="orbit"/> ||align=center style="background-color: #DDDDDD"| Regulus B ||align=center rowspan=2 style="background-color: #DDDDDD"| 2.1 ||align=center rowspan=2 style="background-color: #DDDDDD"| 60 ||align=center rowspan=2 style="background-color: #DDDDDD"| 600 years ||align=center style="background: {{star-color|K}}; | K2V ||align=center| 0.78 ||align=center| 8.1 |- |align=center style="background-color: #DDDDDD"| Regulus C ||align=center style="background: {{star-color|M}}; | M4V ||align=center| 0.32 ||align=center| 13.5 |- |align=center colspan=3| SDSS J1007+1930 ||align=center| 27,200 ||align=center| 800,000 ||align=center| 200 million<br />years ||align=center style="background: {{star-color|L}}; | L9 ||align=center| 0.06 ||align=center| 26 |} {{reflist|group="orbit note"}} == Etymology and cultural associations == ''Rēgulus'' is [[Latin]] for 'prince' or 'little king';<ref name=lands/> its [[Greek language|Greek]] equivalent is Basiliskos or, in Latinised form, Basiliscus.<ref name=Geminus/><ref name=lsj/><ref name=ridpath/> The name Regulus first appeared in the early 16th century.<ref name=ridpath/> It is also known as Qalb al-Asad, from the [[Arabic language|Arabic]] قلب الأسد, meaning 'the heart of the lion', a name already attested in the Greek Kardia Leontos<ref name=Geminus/><ref name=lsj2/> whose Latin equivalent is Cor Leōnis. The Arabic phrase is sometimes approximated as Kabelaced.<ref name=pultar/> In Chinese it is known as 軒轅十四, the Fourteenth Star of Xuanyuan, the [[Yellow Emperor]]. In [[Indian astronomy]], Regulus corresponds to the [[Nakshatra]] [[Magha (nakshatra)|Magha]] ("the bountiful"). [[Babylonia]]ns called it ''Sharru'' ("the King"), and it marked the 15th ecliptic constellation. In [[India]] it was known as ''Maghā'' ("the Mighty"), in [[Sogdia]]na ''Magh'' ("the Great"), in [[Persia]] ''Miyan'' ("the Centre") and also as one of the four '[[royal stars]]' of the Persian monarchy.<ref name=allen/> It was one of the fifteen [[Behenian fixed star|Behenian stars]] known to [[medieval]] [[astrologer]]s, associated with [[granite]], [[mugwort]], and the [[Kabbalah|kabbalistic]] symbol [[File:Agrippa1531 corLeonis.png]]. In the Babylonian [[MUL.APIN]], Regulus is listed as [[Lugal]], meaning king, with co-descriptor, "star of the Lion's breast".<ref name=rogers/> ==See also== * [[Table of stars with Bayer designations]] * [[List of nearest stars by spectral type#List of nearest B-type stars|List of nearest B-type stars]] == Notes == {{Notelist|group=note}} == References == {{reflist|refs= <ref name=edr3>{{cite Gaia EDR3|3880785530720066176}}</ref> <ref name=rogers>{{cite journal | last=Rogers | first=J. H. | title=Origins of the ancient constellations: I. The Mesopotamian traditions | journal=Journal of the British Astronomical Association |issue=1 | volume=108 | pages=9–28 |date=February 1998 | bibcode=1998JBAA..108....9R}}</ref> <ref name=Anderson2012>{{cite journal | title=XHIP: An extended hipparcos compilation | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | s2cid=119257644 }}</ref> <ref name="rappaport2009">{{cite journal | last1=Rappaport | first1=S. | last2=Podsiadlowski | first2=Ph. | last3=Horev | first3=I. | title=The Past and Future History of Regulus | date=2009 | journal=The Astrophysical Journal | volume=698 | issue=1 | pages=666–675 | bibcode=2009ApJ...698..666R | doi=10.1088/0004-637X/698/1/666 |arxiv = 0904.0395 | s2cid=15519189 }}</ref> <ref name=aj129_3_1642>{{cite journal | last1=Fitzpatrick | first1=E. L. | last2=Massa | first2=D. | title=Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry | journal=The Astronomical Journal | volume=129 | issue=3 | pages=1642–1662 |date=March 2005 | doi=10.1086/427855 | bibcode=2005AJ....129.1642F |arxiv = astro-ph/0412542 | s2cid=119512018 }}</ref> <ref name="planets">{{cite web |title=Occultations of bright stars by planets between 0 and 4000 |url=http://www.pierpaoloricci.it/dati/occpiastelle_eng.htm |access-date=2007-10-16}}</ref> <ref name="SOHO">{{cite web |url=https://sungrazer.nrl.navy.mil/index.php?p=transits/noteables |title=Notable objects in LASCO C3 |work=Sungrazing Comets |publisher=Navy.mil |first=Karl |last=Battams |access-date=2012-09-05 |archive-date=2017-01-09 |archive-url=https://web.archive.org/web/20170109000138/https://sungrazer.nrl.navy.mil/index.php?p=transits%2Fnoteables |url-status=live }}</ref> <ref name="van Belle2009">{{cite journal | title=Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars | last1=van Belle | first1=Gerard T. | last2=von Braun | first2=Kaspar | journal=The Astrophysical Journal | volume=694 | issue=2 | pages=1085–1098 | date=2009 | arxiv=0901.1206 | bibcode=2009ApJ...694.1085V | doi=10.1088/0004-637X/694/2/1085 | s2cid=18370219 }}</ref> <ref name="van Leeuwen2007">{{cite journal | title=Validation of the new Hipparcos reduction | url=http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2007A%2526A...474..653VFUL | last1=van Leeuwen | first1=F. | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | date=2007 | arxiv=0708.1752 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |s2cid = 18759600}} [http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/311/hip2&recno=49513 Vizier catalog entry ]</ref> <ref name=tycho2>{{cite journal|bibcode=2000A&A...355L..27H|title=The Tycho-2 catalogue of the 2.5 million brightest stars|journal=Astronomy and Astrophysics|volume=355|pages=L27|last1=Høg|first1=E.|last2=Fabricius|first2=C.|last3=Makarov|first3=V. V.|last4=Urban|first4=S.|last5=Corbin|first5=T.|last6=Wycoff|first6=G.|last7=Bastian|first7=U.|last8=Schwekendiek|first8=P.|last9=Wicenec|first9=A.|year=2000|doi=10.1888/0333750888/2862|isbn=978-0333750889}}</ref> <ref name=dr2>{{cite DR2|3880785182830511232}}</ref> <ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|pages=02025|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009|display-authors=etal}}</ref> <ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|pages=0|last1=Ducati|first1=J. R.|year=2002}}</ref> <ref name=martin>{{cite journal|bibcode=1992A&A...257..186M|title=On the post-T-Tauri nature of late-type visual companions to B-type stars|journal=Astronomy and Astrophysics|volume=257|pages=186|last1=Martin|first1=E. L.|last2=Magazzu|first2=A.|last3=Rebolo|first3=R.|year=1992}}</ref> <ref name=tokovinin>{{cite journal|bibcode= 1997A&AS..124...75T|title= MSC – a catalogue of physical multiple stars|journal= Astronomy and Astrophysics Supplement Series|volume= 124|pages= 75–84|last1= Tokovinin|first1= A. A.|year= 1997|doi= 10.1051/aas:1997181|doi-access= free}}</ref> <ref name=gies>{{cite journal|title=A Spectroscopic Orbit for Regulus|author=Gies, D.R.|display-authors=etal|date=2008|journal=[[The Astrophysical Journal]]|volume=682|issue=2|pages=L117–L120|doi=10.1086/591148|bibcode=2008ApJ...682L.117G|arxiv = 0806.3473 |last2=Dieterich|first2=S.|last3=Richardson|first3=N. D.|last4=Riedel|first4=A. R.|last5=Team|first5=B. L.|last6=McAlister|first6=H. A.|last7=Bagnuolo, Jr.|first7=W. G.|last8=Grundstrom|first8=E. D.|last9=Štefl|first9=S.|last10=Rivinius|first10=Th.|last11=Baade|first11=D.|s2cid=118491233}}</ref> <ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}}</ref> <ref name="WGSN1">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}}</ref> <ref name="IAU-CSN">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}}</ref> <ref name="pugh">{{cite book|title=The Science and Art of Using Telescopes|last1=Pugh|first1=Philip|year=2009|isbn=978-0-387-76469-6|series=Patrick Moore's Practical Astronomy Series|pages=157–185|chapter=Simple Deep Sky Viewing|doi=10.1007/978-0-387-76470-2_6}}</ref> <ref name="rhodope">{{cite journal|bibcode=2008mgm..conf.2594S|title=Asteroidal Occultation of Regulus:. Differential Effect of Light Bending|journal=THE ELEVENTH MARCEL GROSSMANN MEETING on Recent Developments in Theoretical and Experimental General Relativity|pages=2594–2596|last1=Sigismondi|first1=Costantino|last2=Troise|first2=Davide|year=2008|doi=10.1142/9789812834300_0469|isbn=9789812834263}}</ref> <ref name="ridpath">{{cite web | url=http://www.ianridpath.com/startales/leo.html#regulus | title=Ian Ridpath's Star Tales – Regulus, the little king|access-date=20 Feb 2024}}</ref> <ref name=sigismondi>{{cite journal|bibcode=2014ATel.5987....1S|title=Stellar limb darkening scan during 163 Erigone asteroidal occultation of Regulus on March 20, 2014 at 6:06 UT|journal=The Astronomer's Telegram|volume=5987|pages=1|last1=Sigismondi|first1=C.|last2=Flatres|first2=T.|last3=George|first3=T.|last4=Braga-Ribas|first4=F.|year=2014}}</ref> <ref name=apj628>{{cite journal | author=McAlister, H. A. | author2=ten Brummelaar, T. A. | display-authors=etal | title=First Results from the CHARA Array. I. An Interferometric and Spectroscopic Study of the Fast Rotator Alpha Leonis (Regulus) | journal=The Astrophysical Journal | date=2005 | volume=628 | issue=1 | pages=439–452 | doi=10.1086/430730 | bibcode=2005ApJ...628..439M |arxiv = astro-ph/0501261 | last3=Gies | last4=Huang | last5=Bagnuolo, Jr. | last6=Shure | last7=Sturmann | last8=Sturmann | last9=Turner | last10=Taylor | last11=Berger | last12=Baines | last13=Grundstrom | last14=Ogden | last15=Ridgway | last16=Van Belle | s2cid=6776360 }}</ref> <ref name="Cotton2017">{{cite journal|doi=10.1038/s41550-017-0238-6|title=Polarization due to rotational distortion in the bright star Regulus|journal=Nature Astronomy|volume=1|issue=10|pages=690–696|year=2017|last1=Cotton|first1=Daniel V|last2=Bailey|first2=Jeremy|last3=Howarth|first3=Ian D|last4=Bott|first4=Kimberly|last5=Kedziora-Chudczer|first5=Lucyna|last6=Lucas|first6=P. W|last7=Hough|first7=J. H|bibcode=2017NatAs...1..690C|arxiv=1804.06576|s2cid=53560815}}</ref> <ref name="wds">{{cite journal|bibcode= 2001AJ....122.3466M|title= The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog|journal= The Astronomical Journal|volume= 122|issue= 6|pages= 3466–3471|last1= Mason|first1= Brian D.|last2= Wycoff|first2= Gary L.|last3= Hartkopf|first3= William I.|last4= Douglass|first4= Geoffrey G.|last5= Worley|first5= Charles E.|year= 2001|doi= 10.1086/323920|doi-access= free}}</ref> <ref name=Geminus>{{cite book|author1=Geminus|author2=James Evans|author3=J. L. Berggren|title=Geminos's Introduction to the Phenomena: A Translation and Study of a Hellenistic Survey of Astronomy|url=https://books.google.com/books?id=HPBE3RbeceQC|date=29 October 2006|publisher=Princeton University Press|isbn=978-0-691-12339-4}}</ref> <ref name=lindroos>{{cite journal|bibcode= 1985A&AS...60..183L|title= A study of visual double stars with early type primaries. IV Astrophysical data|journal= Astronomy and Astrophysics Supplement Series|volume= 60|pages= 183|last1= Lindroos|first1= K. P.|year= 1985}}</ref> <ref name=allen>{{cite book|last1=Allen|first1=Richard Hinckley|author-link=Richard Hinckley Allen|title=Star Names: Their Lore and Meaning|date=1963|orig-date=1899|publisher=[[Dover Publications]]|pages=[https://archive.org/details/starnamestheirlo00alle/page/255 255–6]|url-access=registration|url=https://archive.org/details/starnamestheirlo00alle/page/255}}</ref> <ref name=pratt>{{cite web |url=http://www.johnpratt.com/items/astronomy/zodiac/zodiac_stars.html |website=John Pratt's stars |title=Zodiac Stars <!--comment=computation published online by Dr J.P. Pratt (Doctor of Astronomy, University of Arizona) of sidereal coordinate data. Note: possibly a non-book published source--> |access-date=2019-06-23}}</ref> <ref name=iota>{{cite web |url=http://www.occultations.org/Regulus2014 |title=Regulus 2014 |publisher=International Occultation Timing Association |access-date=2019-06-23 |archive-date=2020-11-21 |archive-url=https://web.archive.org/web/20201121183357/http://occultations.org/Regulus2014/ |url-status=dead }}</ref> <ref name=skymap>{{cite web |url=http://in-the-sky.org/skymap.php?year=2019&month=4&day=9 |title=In the Sky |access-date=2019-06-23}}</ref> <ref name=lands>{{L&S|regulus1|regulus|ref}}</ref> <ref name=lsj>{{LSJ|basili/skos|βασιλίσκος|ref}}.</ref> <ref name=lsj2>{{LSJ|kardi/a&highlight{{=}}Regulus|καρδία|shortref}}.</ref> <ref name="Gies2020">{{cite journal | title=Spectroscopic Detection of the Pre-White Dwarf Companion of Regulus | last1=Gies | first1=Douglas R. | last2=Lester | first2=Kathryn V. | last3=Wang | first3=Luqian | last4=Couperus | first4=Andrew | last5=Shepard | first5=Katherine | last6=Neiner | first6=Coralie | last7=Wade | first7=Gregg A. | last8=Dunham | first8=David W. | last9=Dunham | first9=Joan B. | display-authors=1 | journal=The Astrophysical Journal | volume=902 | issue=1 | at=Table 3 | year=2020 | arxiv=2009.02409 | bibcode=2020ApJ...902...25G | doi=10.3847/1538-4357/abb372 | doi-access=free }}</ref> <ref name=johnson1983>{{cite journal | last1=Johnson | first1=H. M. | last2=Wright | first2=C. D. | title=Predicted infrared brightness of stars within 25 parsecs of the Sun | journal=Astrophysical Journal Supplement Series | volume=53 | pages=643–711 | date=1983 | doi=10.1086/190905 | bibcode=1983ApJS...53..643J | doi-access=free}}</ref> <ref name=baines>{{cite journal |last1=Baines | first1= Ellyn K.|last2=Armstrong| first2= J. Thomas|last3=Schmitt| first3=Henrique R.|last4= Zavala| first4= R. T.|last5= Benson| first5= James A.|last6= Hutter| first6= Donald J.|last7=Tycner| first7= Christopher |last8=van Belle| first8= Gerard T. |title=Fundamental parameters of 87 stars from the Navy Precision Optical Interferometer |journal=The Astronomical Journal |date=2017 |volume=155 |issue=1 |pages=16 |doi=10.3847/1538-3881/aa9d8b | bibcode= 2018AJ....155...30B | arxiv=1712.08109 | s2cid= 119427037| doi-access= free}}</ref> <ref name=che>{{Cite journal |last1=Che |first1=X. |last2=Monnier |first2=J. D. |last3=Zhao |first3=M. |last4=Pedretti |first4=E. |last5=Thureau |first5=N. |last6=Mérand |first6=A. |last7=ten Brummelaar |first7=T. |last8=McAlister |first8=H. |last9=Ridgway |first9=S. T. |last10=Turner |first10=N. |last11=Sturmann |first11=J. |last12=Sturmann |first12=L. |date=2011-04-18 |title=Colder and Hotter: Interferometric imaging of β Cassiopeiae and α Leonis |journal=The Astrophysical Journal |volume=732 |issue=2 |pages=68 |doi=10.1088/0004-637x/732/2/68 |arxiv=1105.0740 |bibcode=2011ApJ...732...68C |issn=0004-637X}}</ref> <ref name=casagrande2011>{{cite journal | last1=Casagrande | first1=L. | last2=Schönrich | first2=R. | last3=Asplund | first3=M. | last4=Cassisi | first4=S. | last5=Ramírez | first5=I. | last6=Meléndez | first6=J. | last7=Bensby | first7=T. | last8=Feltzing | first8=S. | title=New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey | journal=Astronomy & Astrophysics | display-authors=1 | volume=530 | issue=A138 | pages=21 | date=2011 | doi=10.1051/0004-6361/201016276 | bibcode=2011A&A...530A.138C | arxiv=1103.4651 | s2cid=56118016 }}</ref> <ref name="Mamajek+Burgasser2024">{{Cite journal |last1=Mamajek |first1=Eric E. |last2=Burgasser |first2=Adam J. |date=December 2024 |title=SDSS J100711.74+193056.2: A Candidate Common Motion Substellar Companion to the Nearest B-type Star Regulus |journal=[[The Astronomical Journal]] |language=en |volume=169 |issue=2 |pages=77 |doi=10.3847/1538-3881/ad991b |doi-access=free |arxiv=2412.04599 |issn=1538-3881}}</ref> <ref name=pultar>{{cite web|url=https://www.pultar.org/~mustafa/YAS/K.html|title=YILDIZ ADLARI SÖZLÜĞÜ - K|trans-title=Glossary of Star Names - K|lang=tr|last=Pultar|first=Mustafa|author-link=Mustafa Pultar|access-date=2025-05-04}}</ref> </ref> }} ==External links== {{commons category|Regulus (star)}} * [https://www.nsf.gov/news/news_summ.jsp?cntn_id=100726&org=NSF&from=news Portrait of a Star on the Edge] * [http://www.universetoday.com/am/publish/egg_regulus_spinning.html?2112005 Egg-Shaped Regulus is Spinning Fast] * [[Astronomy Picture of the Day|APOD]] Pictures: :*[http://antwrp.gsfc.nasa.gov/apod/ap990802.html Regulus Occulted] :*[http://antwrp.gsfc.nasa.gov/apod/ap060619.html Regulus & Leo 1 Dwarf Galaxy] :*[http://apod.nasa.gov/apod/ap120110.html Bright Star Regulus near the Leo I Dwarf Galaxy] :*[http://antwrp.gsfc.nasa.gov/apod/ap100610.html Regulus, Mars & Coma Star Cluster] * {{cite web | title=Regulus 3 | work=SolStation | url=http://www.solstation.com/stars2/regulus3.htm | access-date=December 1, 2005}} {{Stars of Leo}} {{Notable stars and star systems coplanar with the solar system}} {{Portal bar|Astronomy|Stars|Outer space}} {{Sky|10|08|22.3|+|11|58|02}} {{DEFAULTSORT:Regulus}} <!-- Properties --> [[Category:B-type subgiants]] [[Category:K-type main-sequence stars]] [[Category:M-type main-sequence stars]] [[Category:Multiple star systems|?]] <!-- Location/Catalogues --> [[Category:Leo (constellation)]] [[Category:Bayer objects|Leonis, Alpha]] [[Category:Bright Star Catalogue objects|3982]] [[Category:Durchmusterung objects]] [[Category:Flamsteed objects|Leonis, 32]] [[Category:Gliese and GJ objects|9316]] [[Category:Henry Draper Catalogue objects|087884 901]] [[Category:Hipparcos objects|049669]] [[Category:Stars with proper names]] [[Category:White dwarfs]]
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