{{short description|Binary star system in the constellation Vela}} {{Starbox begin | name = Kappa Velorum<br/>(Markeb) }} {{Starbox image | image= {{Location mark |image=Vela constellation map.svg |float=center |alt= |label= |position=right |width=280 |mark=Red circle.svg |mark_width=12 |mark_link=κ Velorum |x=553|y=640 }} |caption=Location of κ Vel (circled) }} {{Starbox observe | epoch = J2000 | ra = {{RA|09|22|06.81761}}<ref name=aaa474_2_653/> | dec = {{DEC|−55|00|38.4017}}<ref name=aaa474_2_653/> | appmag_v = 2.48<ref name=aaass27_343/> | constell = Vela }} {{Starbox character | class = B2 V-IV + BV<ref name=Rowan2025/> | b-v = −0.20<ref name=aaass27_343/> | u-b = −0.78<ref name=aaass27_343/> | variable = }} {{Starbox astrometry | radial_v = {{val|21.8|0.8}}<ref name=Rowan2025/> | prop_mo_ra = −11.40<ref name=aaa474_2_653/> | prop_mo_dec = +11.52<ref name=aaa474_2_653/> | parallax = 5.70 | p_error = 0.30 | parallax_footnote = <ref name=aaa474_2_653/> | absmag_v = −3.74<ref name=Anderson2012/> }} {{Starbox orbit | reference = <ref name=Rowan2025/> | period_unitless = {{val|116.795|0.002}} days | axis_unitless = 1.28 AU{{Efn|name=axis}} | eccentricity = {{val|0.1761|0.0004}} | inclination = {{val|74.03|0.02}} | node = {{Val|109.74|0.03}} | periarg = {{val|95.79|0.07}} | k1 = {{val|44|1}} }} {{starbox detail | component1 = A | source = | mass = {{val|13|3|2}}<ref name=Rowan2025/> | radius = {{solar radius calculator|type=logLT|1=4.12|logLerr=0.05|2=18197|Terr=420|decimals=1}}<ref name=Paunzen2021/>{{efn|name=radius}} | luminosity = {{val|13200|1600|1400|fmt=commas}}<ref name=Paunzen2021/> | temperature = {{val|18200|400|fmt=commas}}<ref name=Paunzen2021/> | gravity = 3.5<ref name=Rowan2025/> | metal_fe = {{val|-0.3}}<ref name=Rowan2025/> | rotational_velocity = 39<ref name=Rowan2025/> | age_myr = 40<ref name=Rowan2025/> | component2 = B | mass2 = {{val|7.7|0.9|0.8}}<ref name=Rowan2025/> | temperature2 = {{val|19000|fmt=commas}}<ref name=Rowan2025/> | metal2_fe = {{val|-0.3}}<ref name=Rowan2025/> | age_myr2 = 40<ref name=Rowan2025/> }} {{Starbox catalog | names = Markeb, HR 3734, HD 81188, SAO 236891, FK5 353, CPD−54°2219, GC 12938, HIP 45941<ref name=SIMBAD/> }} {{Starbox reference | Simbad = kap+Vel }} {{Starbox end}}
'''Kappa Velorum''' ('''κ Velorum''', abbreviated '''Kappa Vel''', '''κ Vel'''; proper name '''Markeb'''<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars | publisher=IAU.org | access-date=16 December 2017 | archive-date=10 March 2025 | archive-url=https://web.archive.org/web/20250310063743/https://www.iau.org/public/themes/naming_stars/ | url-status=dead }}</ref> {{IPAc-en|'|m|ɑr|k|E|b}}) is a binary star system in the southern constellation of Vela. The two components are designated Kappa Velorum A and B.
From parallax measurements, this system is located at a distance of roughly {{Convert|572|ly|pc|abbr=off|lk=on}} from the Sun. The apparent visual magnitude is 2.48,<ref name=aaass27_343/> making it readily visible to the naked eye in the southern hemisphere. It forms part of an asterism known as the False Cross along with Delta Velorum, Iota Carinae and Epsilon Carinae, so called because it is sometimes mistaken for the Southern Cross, causing errors in astronavigation.<ref>{{cite book|last=Moore|first=Patrick|title=Patrick Moore's Astronomy: Teach Yourself|publisher=Hachette |year=2010|isbn=978-1444129779|url=https://books.google.com/books?id=D7M0Rgc1ONAC&pg=PT127}}</ref>
==Nomenclature==
''κ Velorum'' (Latinised to ''Kappa Velorum'') is the system's Bayer designation. The designations of the two components as ''Kappa Velorum A'' and ''B'' derives from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).<ref name="planetnaming">{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U. }}</ref>
The system had a traditional name ''Markab'',<ref name=burnham1978/> from the Arabic مركب, ''markab'' meaning "something to ride".<ref name=allen>{{cite book |last = Allen |first = R. H. |author-link = Richard Hinckley Allen |date = 1963 |title = Star Names: Their Lore and Meaning |edition = rep. |publisher = Dover Publications Inc |location = New York, NY |isbn = 0-486-21079-0 }}</ref> It was often spelled ''Markeb''<ref name=jha17_1_51/> to distinguish it from similarly named stars such as Alpha Pegasi. In 2016, the IAU organized a Working Group on Star Names (WGSN)<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 | archive-date=29 September 2018 | archive-url=https://web.archive.org/web/20180929151752/https://www.iau.org/science/scientific_bodies/working_groups/280/ | url-status=dead }}</ref> to catalog and standardize proper names for stars. The WGSN approved the name ''Markeb'' for Kappa Velorum on 5 September 2017. ''Markab'' had previously been approved for Alpha Pegasi on 30 June 2016. Both are now included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>
In Chinese, {{lang|zh|天社}} ({{lang|zh-Latn|Tiān Shè}}), meaning ''Celestial Earth God's Temple'', refers to an asterism consisting of Kappa Velorum, Gamma<sup>2</sup> Velorum, b Velorum and Delta Velorum.<ref>{{in lang|zh}} ''中國星座神話'', written by 陳久金. Published by 台灣書房出版有限公司, 2005, {{ISBN|978-986-7332-25-7}}.</ref> Consequently, Kappa Velorum itself is known as {{lang|zh|天社五}} ({{lang|zh-Latn|Tiān Shè wǔ}}), "the Fifth Star of Celestial Earth God's Temple".<ref>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm 香港太空館 – 研究資源 – 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |date=2008-10-25 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref>
==Properties==
Kappa Velorum is a spectroscopic binary system consisting of a pair of stars that complete an orbit around each other with a period of 116.80 days, a semi-major axis of 1.28 AU{{Efn|name=axis}} and an eccentricity of 0.1761.<ref name=Rowan2025/>
The primary's stellar classification of the pair is B2 V{{snd}}IV, which matches the class of a B-type star that is exhausting the hydrogen at its core and has begun to evolve into a subgiant star. It is about 13 times more massive than the Sun,<ref name=Rowan2025/> with a photospheric radius twelve times larger, irradiating 13,000 times more luminosity than the Sun at an effective temperature of {{val|18000|ul=K|fmt=commas}},<ref name=Paunzen2021/> which give Kappa Velorum A the blue-white hue typical of B-type stars.<ref name=csiro/>
The secondary is a B-type main-sequence star much less luminous than the primary. It has 7.7 times the mass of the Sun and an effective temperature of 19,000 K,<ref name=Rowan2025/> also giving it a blue-white hue.<ref name=csiro/>
=== Interstellar medium ===
Analysis of the spectrum of Kappa Velorum shows absorption lines due to the interstellar medium between Earth and the star. Observation of these features over many years has shown that the lines vary in strength, probably caused by a small dense cloud extending 100–1,000 au moving across the line of sight.<ref name=mnras334_2_L33/><ref>{{cite journal|bibcode=2013MNRAS.429..939S|doi=10.1093/mnras/sts310|title=Small-scale structure in the interstellar medium: Time-varying interstellar absorption towards κ Velorum|journal=Monthly Notices of the Royal Astronomical Society|volume=429|issue=2|pages=939|year=2013|last1=Smith|first1=K. T.|last2=Fossey|first2=S. J.|last3=Cordiner|first3=M. A.|last4=Sarre|first4=P. J.|last5=Smith|first5=A. M.|last6=Bell|first6=T. A.|last7=Viti|first7=S.|author7-link=Serena Viti|doi-access=free |arxiv = 1210.8136 }}</ref>
{{clear}}
==Notes== {{Notelist|notes=
{{Efn|name=radius|1=Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K:<math display="block">\sqrt{\biggl(\frac{5,772}{10^{4.26}}\biggr)^4 \cdot 10^{4.12}} = 11.55\ R_\odot.</math>}}
{{Efn|name=axis|1=Calculated using the parallax of 5.7 milliarcseconds and the separation of 7.272 milliarcseconds. 7.272" / 5.70" = 1.28 AU.}}
}}
== References == {{reflist|25em|refs=
<ref name=aaa474_2_653>{{citation | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 | s2cid=18759600 }}</ref>
<ref name=csiro>{{citation | title=The Colour of Stars | date=December 21, 2004 | work=Australia Telescope, Outreach and Education | publisher=Commonwealth Scientific and Industrial Research Organisation | url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | accessdate=2012-01-16 | archive-date=2013-12-03 | archive-url=https://web.archive.org/web/20131203222826/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | url-status=dead }}</ref>
<ref name=Rowan2025>{{Cite arXiv |mode=cs2 |last1=Rowan |first1=D. M. |last2=Kraus |first2=S. |last3=Thompson |first3=Todd A. |title=Hidden in Plain Sight II: Characterizing the luminous companion to Kappa Velorum with VLTI/GRAVITY |date=2025-12-01 |class=astro-ph.SR |eprint=2512.02116 }}</ref>
<ref name=Paunzen2021>{{Citation |last1=Paunzen |first1=E |last2=Supíková |first2=J |last3=Bernhard |first3=K |last4=Hümmerich |first4=S |last5=Prišegen |first5=M |date=2021-07-01 |title=Magnetic chemically peculiar stars investigated by the Solar Mass Ejection Imager |journal=Monthly Notices of the Royal Astronomical Society |volume=504 |issue=3 |pages=3758–3772 |doi=10.1093/mnras/stab1100 |doi-access=free |arxiv=2105.02206 |bibcode=2021MNRAS.504.3758P |issn=0035-8711}}</ref>
<ref name=aaass27_343>{{citation | last1=Denoyelle | first1=J. | title=The spatial distribution of young stars in Vela (l = 257 to 284 ) | journal=Astronomy and Astrophysics Supplement Series | volume=27 | pages=343–365 |date=March 1977 | bibcode=1977A&AS...27..343D }}</ref>
<ref name=mnras334_2_L33>{{citation | last1=Crawford | first1=I. A. | title=Detection of CaI and CH absorption at the velocity of the variable interstellar component towards κ Velorum | journal=Monthly Notices of the Royal Astronomical Society | volume=334 | issue=2 | pages=L33–L37 |date=August 2002 | doi=10.1046/j.1365-8711.2002.05730.x | bibcode=2002MNRAS.334L..33C | doi-access=free }}</ref>
<ref name=SIMBAD>{{citation | title=kap Vel -- Spectroscopic binary | website=SIMBAD |publisher=Centre de Données astronomiques de Strasbourg | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Kappa+Velorum | access-date=2012-01-08 }}</ref>
<ref name=jha17_1_51>{{citation | last1=Kunitzsch | first1=P. | title=John of London and his Unknown Arabic Sources | journal=Journal for the History of Astronomy | volume=17 | issue=1 | page=51 |date=February 1986 | bibcode=1986JHA....17...51K | doi=10.1177/002182868601700104 | s2cid=118089032 }}</ref>
<ref name=burnham1978>{{citation | first1=Robert | last1=Burnham | title=Burnham's celestial handbook: an observer's guide to the universe beyond the solar system | volume=3 | series=Dover books explaining science | edition=2nd | publisher=Courier Dover Publications | date=1978 | isbn=0-486-23673-0 | page=2037 | url=https://books.google.com/books?id=PJzIt3SIlkUC&pg=PA2037 | access-date=2012-01-08 }}</ref>
<ref name=Anderson2012>{{citation | 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 | postscript=. }}</ref>
}}
==External links== * "The path of the Southern Celestial Pole": The System of W. B. Yeats's A Vision [http://www.yeatsvision.com/Astronomy.html] Diagram of the southern precession circle, showing Markeb as the South Pole Star in 9000 AD. * {{citation | first1=James B. | last1=Kaler | title=MARKEB (Kappa Velorum) | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/markeb.html | access-date=2012-01-08 }}
{{Stars of Vela}}
{{Authority control}}
Velorum, Kappa 081188 045941 3734 Category:Vela (constellation) Category:B-type subgiants Category:Spectroscopic binaries PD-54 02219 Category:Southern pole stars Markeb Category:Brightest stars