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12 Canis Majoris

A visual band light curve for HK Canis Majoris (2020)
Observation data Epoch J2000      Equinox J2000
Constellation	Canis Major
Right ascension	06 47 01.48353
Declination	−21° 00′ 55.4517″
Apparent magnitude (V)	+6.07
Characteristics
Spectral type	B7 II/III or B5 V
B−V color index	−0.159±0.004
Variable type	SX Ari
Astrometry
Radial velocity (Rv)	+16.4±2.5 km/s
Proper motion (μ)	RA: −14.568 mas/yr Dec.: +5.778 mas/yr
Parallax (π)	4.6155 ± 0.0543 mas
Distance	707 ± 8 ly (217 ± 3 pc)
Absolute magnitude (MV)	−0.81
Details
Mass	4.8 M☉
Radius	2.73 R☉
Luminosity	537 L☉
Surface gravity (log g)	4.23 cgs
Temperature	15,830±60 K
Metallicity	−0.37 dex
Rotation	2.18045 d
Rotational velocity (v sin i)	65 km/s
Age	134 Myr
Other designations
12 Cep, HK CMa, BD−20°1576, FK5 817, GC 8884, HD 49333, HIP 32504, HR 2509, SAO 172318
Database references
SIMBAD	data

12 Canis Majoris is a variable star located about 707 light years away from the Sun in the southern constellation of Canis Major. It has the variable star designation HK Canis Majoris; 12 Canis Majoris is the Flamsteed designation. This body is just barely visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of +6.07. It is moving away from the Earth with a heliocentric radial velocity of +16 km/s. This is the brightest star in the vicinity of the open cluster NGC 2287, although it is probably not a member based on its proper motion.

This star has a stellar classification of B7 II/III, matching the spectrum of a B-type star intermediate between a giant and bright giant. (Cidale et al. (2007) show a class of B5 V, which would indicate it is instead a B-type main-sequence star.) It is a magnetic Bp star of the helium–weak variety (CP4), with the spectrum displaying evidence for vertical stratification of helium in the atmosphere.

Holger Pedersen and Bjarne Thomsen discovered that 12 Canis Majoris is a variable star, in 1977. It was given its variable star designation in 1981. Samus et al. (2017) classify it as an SX Arietis variable that varies in brightness by about 0.05 magnitudes over a period of 2.18045 days. It has 4.8 times the mass of the Sun and 2.73 times the Sun's radius. The star is radiating 537 times the Sun's luminosity from its photosphere at an effective temperature of 15,830 K.

References

1. Bernhard, Klaus; Hũmmerich, Stefan; Paunzen, Ernst (17 February 2020). "New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data". Monthly Notices of the Royal Astronomical Society. 493 (3): 3293–3330. arXiv:2002.06435. Bibcode:2020MNRAS.493.3293B. doi:10.1093/mnras/staa462.
2. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
3. ^ 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.
4. ^ Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
5. ^ Cidale, L. S.; et al. (June 2007), "Fundamental parameters of He-weak and He-strong stars", Astronomy and Astrophysics, 468 (1): 263–272, arXiv:0705.0541, Bibcode:2007A&A...468..263C, doi:10.1051/0004-6361:20066454, S2CID 14143604.
6. ^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
7. ^ Shultz, M. E.; Owocki, S. P.; Ud-Doula, A.; Biswas, A.; Bohlender, D.; Chandra, P.; Das, B.; David-Uraz, A.; Khalack, V.; Kochukhov, O.; Landstreet, J. D.; Leto, P.; Monin, D.; Neiner, C.; Rivinius, Th; Wade, G. A. (2022). "MOBSTER - VI. The crucial influence of rotation on the radio magnetospheres of hot stars". Monthly Notices of the Royal Astronomical Society. 513 (1): 1429. arXiv:2201.05512. Bibcode:2022MNRAS.513.1429S. doi:10.1093/mnras/stac136.
8. ^ Shulyak, D.; et al. (2014), "Interferometry of chemically peculiar stars: Theoretical predictions versus modern observing facilities", Monthly Notices of the Royal Astronomical Society, 443 (2): 1629, arXiv:1406.6093, Bibcode:2014MNRAS.443.1629S, doi:10.1093/mnras/stu1259, S2CID 96452769.
9. ^ Netopil, M.; et al. (November 2008), "Chemically peculiar stars and their temperature calibration", Astronomy and Astrophysics, 491 (2): 545–554, arXiv:0809.5131, Bibcode:2008A&A...491..545N, doi:10.1051/0004-6361:200810325, S2CID 14084961.
10. Mosser, B.; et al. (February 2005), "Seismology and activity of the F type star HD 49933", Astronomy and Astrophysics, 431 (2): L13 – L16, arXiv:astro-ph/0501459, Bibcode:2005A&A...431L..13M, doi:10.1051/0004-6361:200500003, S2CID 18412104.
11. Gontcharov, G. A. (December 2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters. 38 (12): 771–782. arXiv:1606.08814. Bibcode:2012AstL...38..771G. doi:10.1134/S1063773712120031. eISSN 1562-6873. ISSN 1063-7737.
12. ^ "12 CMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved April 30, 2019.
13. Feinstein, A.; et al. (1979), "Multicolor photometry of the open cluster NGC 2287", International Astronomical Union, Reunion Astronomica Regional Latinoamericana, 1st, Santiago, Chile, Jan. 16-21, 1978, vol. 3, Chile, Universidad: Departamento de Astronomia, Publicaciones, pp. 146–149, Bibcode:1979rarl.conf..146F.
14. Levato, H.; Garcia, B. (1984), "Axial rotation in NGC 2287", Astrophysical Letters, 24 (3): 161–164, Bibcode:1984ApL....24..161L.
15. Bailey, J. D.; Landstreet, J. D. (2013), "Abundances determined using Si ii and Si iii in B-type stars: Evidence for stratification", Astronomy & Astrophysics, 551: A30, arXiv:1301.3050, Bibcode:2013A&A...551A..30B, doi:10.1051/0004-6361/201220671, S2CID 59291051.
16. Farthmann, M.; et al. (November 1994), "Stratification of helium in the photospheres of the helium-weak stars HD 28843 and HD 49333", Astronomy and Astrophysics, 291: 919–927, Bibcode:1994A&A...291..919F.
17. Pedersen, H.; Thomsen, B. (October 1977). "Spectrum and photometric variability of He-weak and He-strong stars". Astronomy and Astrophysics, Suppl. Ser. 30: 11–25. Bibcode:1977A&AS...30...11P. Retrieved 1 January 2025.
18. Kholopov, P. N.; Samus, N. N.; Kukarkina, N. P.; Medvedeva, G. I.; Perova, N. B. (February 1981). "65th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 1921. Bibcode:1981IBVS.1921....1K. Retrieved 1 January 2025.

v t e Constellation of Canis Major
Canis Major in Chinese astronomy List of stars in Canis Major
Stars	Bayer α (Sirius) β (Mirzam) γ (Muliphein) δ (Wezen) ε (Adhara) ζ (Furud) η (Aludra) θ ι κ λ μ ν ν ν ξ ξ ο ο π σ (Unurgunite) τ ω Flamsteed 10 11 12 15 17 26 27 29 Variable R W Z UW VY CX EZ FN FS FY LS NR V352 HR 2225 2318 2437 2447 2450 2758 2764 2766 2812 HD 43162 43197 (Amadioha) 45184 45364 47186 54879 Other RX J0720.4−3125 WASP-64 (Atakoraka) WISE 0713−2917 WR 7
Exoplanets ν Canis Majoris b HD 47536 b c HD 47186 b c HD 45364 b c HD 43197 b
Star clusters	NGC NGC 2204 NGC 2354 NGC 2360 NGC 2362 NGC 2374 Other Gaia 1 Messier 41
Nebulae NGC 2359 NGC 2361 Sh2-297
Galaxies	NGC 2207 2217 2227 2280 2283 2293 Other Canis Major Overdensity IC 2163
Astronomical events SN 1999ec SN 2003H
Category

• B-type giants
• B-type bright giants
• B-type main-sequence stars
• Helium-weak stars
• SX Arietis variables
• Canis Major
• Durchmusterung objects
• Flamsteed objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects
• Objects with variable star designations