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Alpha Horologii

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Alpha Horologii
Observation data
Epoch J2000      Equinox J2000
Constellation Horologium
Right ascension 04h 14m 00.114s[1]
Declination −42° 17′ 39.727″ [1]
Apparent magnitude (V) +3.846[2]
Characteristics
Evolutionary stage Giant star
Spectral type K2 III[3]
U−B color index +1.013[4]
B−V color index 1.083±0.037[2]
Astrometry
Radial velocity (Rv)+21.6±0.3[5] km/s
Proper motion (μ) RA: +41.992±0.125 mas/yr[1]
Dec.: −203.157±0.154 mas/yr[1]
Parallax (π)27.721 ± 0.11195 mas[1]
Distance117.6+0.55
−0.52 ly
(36.06+0.17
−0.16 pc)[6]
Absolute bolometric
magnitude (Mbol)		+1.08[7]
Details[2]
Mass1.409±0.265 M☉
Radius9.931±0.351 R☉
Luminosity37.61[8] L☉
Surface gravity (log g)2.82±0.02 cgs
Temperature4695±50 K
Metallicity [Fe/H]−0.03±0.03 dex
Age3.561±2.333 Gyr
Other designations
α Hor, CD−42° 1425, HD 26967, HIP 19747, HR 1326, SAO 216710[9]
Database references
SIMBADdata

Alpha Horologii (α Horologii) is a solitary[10] orange-hued giant star and the brightest star in the constellation Horologium. It is visible to the naked eye with an apparent visual magnitude of +3.85.[2] Based upon an parallax shift of 27.721 mas as seen from the Earth, it is located at a distance of 36 light-years (11 parsecs).[1] The star is moving away from the Sun with a radial velocity of +21.6 km/s.[5]

The stellar classification of K2 III[3] indicates this is an evolved giant star of the K class. This means it has consumed the hydrogen at its core and has migrated away from the main sequence, with its outer envelope cooling and expanding in the process. Alpha Horologii has an estimated 1.41 times the mass of the Sun[2] and is radiating 38[8] times the Sun's luminosity from its photosphere at an effective temperature of 4,695 K.[2] Being 3.56 billion years old, it has swollen to around 10 times the diameter of the Sun,[2] having spent much of its life as a white main sequence star.[11]

References

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  1. ^ a b c d e 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.
  2. ^ a b c d e f g Gomes da Silva, J.; Santos, N. C.; Adibekyan, V.; Sousa, S. G.; Campante, T. L.; Figueira, P.; Bossini, D.; Delgado-Mena, E.; Monteiro, M. J. P. F. G.; de Laverny, P.; Recio-Blanco, A.; Lovis, C. (2021-02-01). "Stellar chromospheric activity of 1674 FGK stars from the AMBRE-HARPS sample. I. A catalogue of homogeneous chromospheric activity". Astronomy and Astrophysics. 646: A77. arXiv:2012.10199. Bibcode:2021A&A...646A..77G. doi:10.1051/0004-6361/202039765. ISSN 0004-6361. Alpha Horologii's database entry at VizieR.
  3. ^ a b Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 250741593.
  4. ^ Cousins, A. W. J. (1973), "Revised zero points and UBV photometry of stars in the Harvard E and F regions", Memoirs of the Royal Astronomical Society, 77: 223–236, Bibcode:1973MmRAS..77..223C.
  5. ^ a b de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  6. ^ Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021-03-01). "Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. arXiv:2012.05220. Bibcode:2021AJ....161..147B. doi:10.3847/1538-3881/abd806. ISSN 0004-6256. Data about this star can be seen here.
  7. ^ Liu, Y. J.; Zhao, G.; Shi, J. R.; Pietrzyński, G.; Gieren, W. (2007). "The abundances of nearby red clump giants". Monthly Notices of the Royal Astronomical Society. 382 (2): 553–66. Bibcode:2007MNRAS.382..553L. doi:10.1111/j.1365-2966.2007.11852.x.
  8. ^ a b McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012). "Fundamental Parameters and Infrared Excesses of Hipparcos Stars". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–57. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. S2CID 118665352.
  9. ^ "Alpha Horologii". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 17 March 2016.
  10. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  11. ^ Kaler, Jim. "Alpha Horologii". James Kaler's Stars. Retrieved 20 September 2019.
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