Kappa Velorum

Kappa Velorum
(Markeb)
	Location of κ Vel (circled)
Observation data; Epoch J2000 Equinox ICRS
Constellation	Vela
Right ascension	09h 22m 06.81761s
Declination	−55° 00′ 38.4017″
Apparent magnitude (V)	2.48
Characteristics
Spectral type	B2 V-IV + BV
U−B color index	−0.78
B−V color index	−0.20
Astrometry
Radial velocity (Rv)	21.8±0.8 km/s
Proper motion (μ)	RA: −11.40 mas/yr ; Dec.: +11.52 mas/yr
Parallax (π)	5.70±0.30 mas
Distance	570 ± 30 ly ; (175 ± 9 pc)
Absolute magnitude (MV)	−3.74
Orbit
Period (P)	116.795±0.002 days
Semi-major axis (a)	1.28 AU
Eccentricity (e)	0.1761±0.0004
Inclination (i)	74.03±0.02°
Longitude of the node (Ω)	109.74±0.03°
Argument of periastron (ω); (secondary)	95.79±0.07°
Semi-amplitude (K1); (primary)	44±1 km/s
Details
A
Mass	13+3; −2 M☉
Radius	11.6 ± 0.9 R☉
Luminosity	13,200+1,600; −1,400 L☉
Surface gravity (log g)	3.5 cgs
Temperature	18,200±400 K
Metallicity [Fe/H]	−0.3 dex
Rotational velocity (v sin i)	39 km/s
Age	40 Myr
B
Mass	7.7+0.9; −0.8 M☉
Temperature	19,000 K
Metallicity [Fe/H]	−0.3 dex
Age	40 Myr
Other designations
	Markeb, HR 3734, HD 81188, SAO 236891, FK5 353, CPD−54°2219, GC 12938, HIP 45941
Database references
SIMBAD	data

Kappa Velorum (κ Velorum, abbreviated Kappa Vel or κ Vel; proper name Markeb /ˈmɑːrkɛb/) is star system in the southern constellation of Vela. It is a binary star consisting of two components, designated A and B; κ Vel A is by far the brighter of the two, so dominates the combined light.

From parallax measurements, this system is located at a distance of roughly 572 light-years (175 parsecs) from the Sun. The apparent visual magnitude is 2.48, 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.

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).

The system had a traditional name Markab, from the Arabic مركب, markab meaning "something to ride". It was often spelled Markeb to distinguish it from Alpha Pegasi, which was also traditionally called Markab. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name Markeb for Kappa Velorum A 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.

In Chinese, 天社 (Tiān Shè), meaning Celestial Earth God's Temple, refers to an asterism consisting of Kappa Velorum, Gamma² Velorum, b Velorum and Delta Velorum. Consequently, Kappa Velorum itself is known as 天社五 (Tiān Shè wǔ), "the Fifth Star of Celestial Earth God's Temple".

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 and an eccentricity of 0.1761.

The primary's stellar classification of the pair is B2 V – 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, with a photospheric radius twelve times larger, irradiating 13,000 times more luminosity than the Sun at an effective temperature of 18,000 K, which give Kappa Velorum A the blue-white hue typical of B-type stars.

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, also giving it a blue-white hue.

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.

Notes

1 2 Calculated using the parallax of 5.7 milliarcseconds and the separation of 7.272 milliarcseconds. 7.272" / 5.70" = 1.28 AU.
↑ 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: ${\sqrt {{\biggl (}{\frac {5,772}{10^{4.26}}}{\biggr )}^{4}\cdot 10^{4.12}}}=11.55\ R_{\odot }.$

References

1 2 3 4 5 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, S2CID 18759600
1 2 3 4 Denoyelle, J. (March 1977), "The spatial distribution of young stars in Vela (l = 257 to 284 )", Astronomy and Astrophysics Supplement Series, 27: 343–365, Bibcode:1977A&AS...27..343D
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Rowan, D. M.; Kraus, S.; Thompson, Todd A. (1 February 2026). "Hidden in Plain Sight II: Characterizing the Luminous Companion to κ Velorum with VLTI/GRAVITY". Publications of the Astronomical Society of the Pacific. 138 (2): 024203. arXiv:2512.02116. doi:10.1088/1538-3873/ae3b75.
↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
1 2 3 4 Paunzen, E; Supíková, J; Bernhard, K; Hümmerich, S; Prišegen, M (2021-07-01), "Magnetic chemically peculiar stars investigated by the Solar Mass Ejection Imager", Monthly Notices of the Royal Astronomical Society, 504 (3): 3758–3772, arXiv:2105.02206, Bibcode:2021MNRAS.504.3758P, doi:10.1093/mnras/stab1100, ISSN 0035-8711
↑ "kap Vel -- Spectroscopic binary", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-08
1 2 "Naming Stars". IAU.org. Archived from the original on 10 March 2025. Retrieved 16 December 2017.
↑ Moore, Patrick (2010). Patrick Moore's Astronomy: Teach Yourself. Hachette. ISBN 978-1444129779.
↑ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
↑ Burnham, Robert (1978), Burnham's celestial handbook: an observer's guide to the universe beyond the solar system, Dover books explaining science, vol. 3 (2nd ed.), Courier Dover Publications, p. 2037, ISBN 0-486-23673-0, retrieved 2012-01-08
↑ Allen, Richard Hinckley (1936) [1899]. Star Names and Their Meanings. New York: G. E. Stechert. p. 66. OCLC 9825499.
↑ Kunitzsch, P. (February 1986), "John of London and his Unknown Arabic Sources", Journal for the History of Astronomy, 17 (1): 51, Bibcode:1986JHA....17...51K, doi:10.1177/002182868601700104, S2CID 118089032
↑ "IAU Working Group on Star Names (WGSN)". Archived from the original on 29 September 2018. Retrieved 22 May 2016.
↑ (in Chinese) 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.
↑ (in Chinese) 香港太空館 – 研究資源 – 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
1 2 "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2013-12-03, retrieved 2012-01-16
↑ Crawford, I. A. (August 2002), "Detection of CaI and CH absorption at the velocity of the variable interstellar component towards κ Velorum", Monthly Notices of the Royal Astronomical Society, 334 (2): L33–L37, Bibcode:2002MNRAS.334L..33C, doi:10.1046/j.1365-8711.2002.05730.x
↑ Smith, K. T.; Fossey, S. J.; Cordiner, M. A.; Sarre, P. J.; Smith, A. M.; Bell, T. A.; Viti, S. (2013). "Small-scale structure in the interstellar medium: Time-varying interstellar absorption towards κ Velorum". Monthly Notices of the Royal Astronomical Society. 429 (2): 939. arXiv:1210.8136. Bibcode:2013MNRAS.429..939S. doi:10.1093/mnras/sts310.

External links

"The path of the Southern Celestial Pole": The System of W. B. Yeats's A Vision Diagram of the southern precession circle, showing Markeb as the South Pole Star in 9000 AD.
Kaler, James B., "MARKEB (Kappa Velorum)", Stars, University of Illinois, retrieved 2012-01-08

[axis-5] 1 2 Calculated using the parallax of 5.7 milliarcseconds and the separation of 7.272 milliarcseconds. 7.272" / 5.70" = 1.28 AU.

[radius-7] 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: ${\sqrt {{\biggl (}{\frac {5,772}{10^{4.26}}}{\biggr )}^{4}\cdot 10^{4.12}}}=11.55\ R_{\odot }.$

[aaa474_2_653-1] 1 2 3 4 5 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, S2CID 18759600

[aaass27_343-2] 1 2 3 4 Denoyelle, J. (March 1977), "The spatial distribution of young stars in Vela (l = 257 to 284 )", Astronomy and Astrophysics Supplement Series, 27: 343–365, Bibcode:1977A&AS...27..343D

[Rowan2025-3] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Rowan, D. M.; Kraus, S.; Thompson, Todd A. (1 February 2026). "Hidden in Plain Sight II: Characterizing the Luminous Companion to κ Velorum with VLTI/GRAVITY". Publications of the Astronomical Society of the Pacific. 138 (2): 024203. arXiv:2512.02116. doi:10.1088/1538-3873/ae3b75.

[Anderson2012-4] Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.

[Paunzen2021-6] 1 2 3 4 Paunzen, E; Supíková, J; Bernhard, K; Hümmerich, S; Prišegen, M (2021-07-01), "Magnetic chemically peculiar stars investigated by the Solar Mass Ejection Imager", Monthly Notices of the Royal Astronomical Society, 504 (3): 3758–3772, arXiv:2105.02206, Bibcode:2021MNRAS.504.3758P, doi:10.1093/mnras/stab1100, ISSN 0035-8711

[SIMBAD-8] "kap Vel -- Spectroscopic binary", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-08

[IAU-LSN-9] 1 2 "Naming Stars". IAU.org. Archived from the original on 10 March 2025. Retrieved 16 December 2017.

[10] Moore, Patrick (2010). Patrick Moore's Astronomy: Teach Yourself. Hachette. ISBN 978-1444129779.

[planetnaming-11] Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].

[burnham1978-12] Burnham, Robert (1978), Burnham's celestial handbook: an observer's guide to the universe beyond the solar system, Dover books explaining science, vol. 3 (2nd ed.), Courier Dover Publications, p. 2037, ISBN 0-486-23673-0, retrieved 2012-01-08

[allen-13] Allen, Richard Hinckley (1936) [1899]. Star Names and Their Meanings. New York: G. E. Stechert. p. 66. OCLC 9825499.

[jha17_1_51-14] Kunitzsch, P. (February 1986), "John of London and his Unknown Arabic Sources", Journal for the History of Astronomy, 17 (1): 51, Bibcode:1986JHA....17...51K, doi:10.1177/002182868601700104, S2CID 118089032

[WGSN-15] "IAU Working Group on Star Names (WGSN)". Archived from the original on 29 September 2018. Retrieved 22 May 2016.

[16] (in Chinese) 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.

[17] (in Chinese) 香港太空館 – 研究資源 – 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.

[csiro-18] 1 2 "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2013-12-03, retrieved 2012-01-16

[mnras334_2_L33-19] Crawford, I. A. (August 2002), "Detection of CaI and CH absorption at the velocity of the variable interstellar component towards κ Velorum", Monthly Notices of the Royal Astronomical Society, 334 (2): L33–L37, Bibcode:2002MNRAS.334L..33C, doi:10.1046/j.1365-8711.2002.05730.x

[20] Smith, K. T.; Fossey, S. J.; Cordiner, M. A.; Sarre, P. J.; Smith, A. M.; Bell, T. A.; Viti, S. (2013). "Small-scale structure in the interstellar medium: Time-varying interstellar absorption towards κ Velorum". Monthly Notices of the Royal Astronomical Society. 429 (2): 939. arXiv:1210.8136. Bibcode:2013MNRAS.429..939S. doi:10.1093/mnras/sts310.