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Kappa Andromedae

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Kappa Andromedae
Location of κ Andromedae (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Andromeda[1]
Right ascension 23h 40m 24.508s[2]
Declination +44° 20′ 02.16″[2]
Apparent magnitude (V) 4.139[3]
Characteristics
Evolutionary stage main sequence[4][2]
Spectral type A0 V[5]
U−B color index −0.221[3]
B−V color index −0.067[3]
Astrometry
Radial velocity (Rv)−12.7±0.8[6] km/s
Proper motion (μ) RA: +79.998 mas/yr[2]
Dec.: −19.011 mas/yr[2]
Parallax (π)19.4064±0.2104 mas[2]
Distance168 ± 2 ly
(51.5 ± 0.6 pc)
Absolute magnitude (MV)+0.59[1]
Details[7]
Mass2.768+0.1
−0.109 M☉
Radius2.303+0.039
−0.016 R☉ (equatorial)
1.959+0.033
−0.028 (polar) R☉
Luminosity62.60+9.83
−2.23 L☉
Surface gravity (log g)3.968+0.028
−0.025 cgs (equatorial)
4.296+0.019
−0.012 (polar) cgs
Temperature10,342+384
−138 K (equatorial)
12,050+448
−39 (polar) K
Rotational velocity (v sin i)142.2+13.1
−21.1 km/s
Age47±7[8] Myr
Other designations
Kaffalmusalsala, κ And, 19 Andromedae, BD+43°4522, FK5 1619, HD 222439, HIP 116805, HR 8976, SAO 53264, PPM 64525[9]
Database references
SIMBADdata
Exoplanet Archivedata

Kappa Andromedae, Latinized from κ Andromedae, formally named Kaffalmusalsala,[10] is a star in the northern constellation of Andromeda. It is visible to the naked eye with an apparent visual magnitude of 4.1.[3] Based on the star's ranking on the Bortle Dark-Sky Scale, it is luminous enough to be visible from the suburbs and from urban outskirts, but not from brightly lit inner city regions. Parallax measurements place it at a distance of approximately 168 light-years (52 parsecs).[2] It is drifting closer with a radial velocity of −13 km/s,[6] and there is a high likelihood (86%) that it is a member of the Beta Pictoris moving group.[11] The star has one known exoplanet, Kappa Andromedae b.[12]

Naming

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Location of κ Andromedae

In traditional Arabic astronomy, the stars ι Andromedae, κ Andromedae, and λ Andromedae were known as Kaff al-Musalsala, the hand of the chained woman (i.e. Andromeda), and as Ra’s al-Nāqa, the head of the she-camel.[13] The IAU Working Group on Star Names approved the name Kaffalmusalsala for κ Andromedae on 8 May 2025 and it is now so entered in the IAU Catalog of Star Names; the name Rasalnaqa was given to ι Andromedae.[10]

In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of κ Andromedae, α Lacertae, 4 Lacertae, π2 Cygni, π1 Cygni, HD 206267, ε Cephei, β Lacertae, σ Cassiopeiae, ρ Cassiopeiae, τ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, the Chinese name for κ Andromedae itself is 螣蛇二十一 (Téng Shé èrshíyī, English: the Twenty First Star of Flying Serpent).[14]

Properties

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The stellar classification of Kappa Andromedae is A0 V[5] indicating that it is a main sequence star fusing hydrogen into helium at its core. The star has an estimated 2.8 times the mass of the Sun and is radiating 62.6 times the Sun's luminosity.[7] It is spinning rapidly, with a projected rotational velocity of 162 km/s. Its true rotational velocity is 283.8 km/s, which is about 85% of its critical rotation rate (the rate at which it would break up).[7] With such a rapid rotation rate, the star is deformed into an oblate spheroid, such that while the polar radius is 1.959 R☉, the equatorial radius is significantly larger, at 2.303 R☉.[7] The outer envelope of the star is radiating energy into space with an effective temperature of 10,342 K at the equator and 12,050 K at its poles, producing a blue-white hue.[7]

The age of Kappa Andromedae has been the subject of debate. The discovery paper for Kappa Andromedae b[12] argued that the primary's kinematics are consistent with membership in the Columba Association, which would imply a system age of 20-50 million years, while a subsequent work derived an older age of 220±100 million years based on the star's position on the Hertzsprung-Russell diagram position assuming that the star is not a fast rotator viewed pole-on.[15] Direct measurements of the star later showed that Kappa Andromedae A is in fact a rapid rotator viewed nearly pole-on and yield a best-estimated age of 47+27
−40 million years.[7] Modelling of the companion Kappa Andromedae b further constrains the age to 47±7 million years.[8]

Substellar companion

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In November 2012, members of the Strategic Explorations of Exoplanets and Disks with Subaru (SEEDS) survey reported the discovery of a faint, directly-imaged companion Kappa Andromedae b.[12] Follow-up photometry and spectroscopy of kappa And b with the Subaru Telescope, Keck Observatory, and Large Binocular Telescope constrained its mass to be about 13 Jupiter masses, temperature to be between 1700 K and 2150 K, and orbit to be highly eccentric with a semimajor axis likely greater than about 75 AU. The companion's spectrum shows evidence for water and carbon monoxide molecules and suggests the object has a low surface gravity.[16][17][18]

The Kappa Andromedae planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(years)		 Eccentricity Inclination
(°)		 Radius
b 17.3±1.8[8] MJ 104+30
−46[19]		 520+450
−230[18]		 0.80+0.05
−0.08[18]		 132.0[18] 1.42±0.06[8] RJ

See also

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References

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  1. 1 2 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. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 6 7 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. 1 2 3 4 Harmanec, P.; et al. (1980). "Photoelectric photometry at the Hvar Observatory. IV - A study of UBV variations of a group of bright northern Be stars". Bulletin of the Astronomical Institutes of Czechoslovakia, Bulletin. 31 (3): 144–159. Bibcode:1980BAICz..31..144H.
  4. ↑ Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy and Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691.
  5. 1 2 Sharma, Kaushal; Kembhavi, Ajit; Kembhavi, Aniruddha; Sivarani, T; Abraham, Sheelu; Vaghmare, Kaustubh (2020-01-11). "Application of convolutional neural networks for stellar spectral classification". Monthly Notices of the Royal Astronomical Society. 491 (2): 2280–2300. arXiv:1909.05459. Bibcode:2020MNRAS.491.2280S. doi:10.1093/mnras/stz3100. ISSN 0035-8711.
  6. 1 2 Gontcharov, G. A. (2006). "Pulkovo compilation of radial velocities for 35495 stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  7. 1 2 3 4 5 6 Jones, Jeremy; et al. (2016). "The Age of the Directly Imaged Planet Host Star κ Andromedae Determined from Interferometric Observations". The Astrophysical Journal Letters. 822 (1): 7. arXiv:1604.02176. Bibcode:2016ApJ...822L...3J. doi:10.3847/2041-8205/822/1/L3. S2CID 38367518.
  8. 1 2 3 4 Godoy, N.; Choquet, E.; Serabyn, E.; Mâlin, M.; Tremblin, P.; Danielski, C.; Lagage, P. O.; Boccaletti, A.; Charnay, B.; Ressler, M. E. (2025-09-30). "A JWST/MIRI view of κ Andromedae b: Refining its mass, age, and physical parameters". Astronomy & Astrophysics. 702: A4. arXiv:2509.03624. doi:10.1051/0004-6361/202554652. ISSN 0004-6361.
  9. ↑ "kap And", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2021-06-01
  10. 1 2 "IAU Catalog of Star Names". Retrieved 8 May 2025.
  11. ↑ Lee, Jinhee; Song, Inseok (July 2019). "Development of models for nearbaby young stellar moving groups: creation, revision, and finalization of the models". Monthly Notices of the Royal Astronomical Society. 486 (3): 3434–3450. arXiv:1904.07157. Bibcode:2019MNRAS.486.3434L. doi:10.1093/mnras/stz1044.
  12. 1 2 3 Carson; et al. (November 2012). "Direct Imaging Discovery of a 'Super-Jupiter' Around the late B-Type Star κ And". The Astrophysical Journal. 763 (2): L32. arXiv:1211.3744. Bibcode:2013ApJ...763L..32C. doi:10.1088/2041-8205/763/2/L32. S2CID 119253577.
  13. ↑ "Kaffalmusalsala (كفّ المسلسة)". All Skies Encyclopaedia. IAU Working Group on Star Names. Retrieved 8 May 2025.
    "al-Nāqa (الناقة)". All Skies Encyclopaedia. IAU Working Group on Star Names. Retrieved 8 May 2025.
  14. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日 Archived 2011-05-21 at the Wayback Machine
  15. ↑ Hinkley, Sasha; Pueyo, Laurent; Faherty, Jacqueline K.; Oppenheimer, Ben R.; Mamajek, Eric E.; Kraus, Adam L.; Rice, Emily L.; Ireland, Michael J.; David, Trevor; et al. (December 2013). "The κ Andromedae System: New Constraints on the Companion Mass, System Age, and Further Multiplicity". The Astrophysical Journal. 779 (2): 153. arXiv:1309.3372. Bibcode:2013ApJ...779..153H. doi:10.1088/0004-637X/779/2/153.
  16. ↑ Currie, Thayne; et al. (2018). "SCExAO/CHARIS Near-infrared Direct Imaging, Spectroscopy, and Forward-Modeling of κ And b: A Likely Young, Low-gravity Superjovian Companion". The Astrophysical Journal. 156 (6): 291. arXiv:1810.09457. Bibcode:2018AJ....156..291C. doi:10.3847/1538-3881/aae9ea. S2CID 119261709.
  17. ↑ Stone, Jordan M.; et al. (December 2020). "High Contrast Thermal Infrared Spectroscopy with ALES: The 3-4μm Spectrum of κ Andromedae b". The Astronomical Journal. 160 (6): 262. arXiv:2010.02928. Bibcode:2020AJ....160..262S. doi:10.3847/1538-3881/abbef3. S2CID 222177297.
  18. 1 2 3 4 Wilcomb, K; et al. (2020). "Moderate-resolution K-band Spectroscopy of Substellar Companion κ Andromedae b". The Astrophysical Journal. 160 (5): 207. arXiv:2009.08959. Bibcode:2020AJ....160..207W. doi:10.3847/1538-3881/abb9b1. S2CID 221802366.
  19. ↑ Uyama, Taichi; et al. (2020). "Atmospheric Characterization and Further Orbital Modeling of κ Andromeda b". The Astrophysical Journal. 159 (2): 40. arXiv:1911.09758. Bibcode:2020AJ....159...40U. doi:10.3847/1538-3881/ab5afa. S2CID 208248220.
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