Zeta Horologii

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Zeta Horologii
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Horologium
Right ascension 02h 40m 39.61286s[1]
Declination −54° 32′ 59.6836″[1]
Apparent magnitude (V) 5.20[2]
Spectral type F6 V[3] (F2 V + F5 V)[4]
B−V color index +0.42[2]
Radial velocity (Rv) 5.8[3] km/s
Proper motion (μ) RA: +32.86[1] mas/yr
Dec.: +4.96[1] mas/yr
Parallax (π) 20.37 ± 0.21[1] mas
Distance 160 ± 2 ly
(49.1 ± 0.5 pc)
Period (P) 12.9274 d
Eccentricity (e) 0.25
Periastron epoch (T) 7.361±0.046
Argument of periastron (ω)
Semi-amplitude (K1)
58.1±1.37 km/s
Semi-amplitude (K2)
66.1±1.56 km/s
ζ Hor A
Mass 1.43[5] M
Surface gravity (log g) 3.74[6] cgs
Temperature 6,702[6] K
Metallicity [Fe/H] −0.07[6] dex
Rotational velocity (v sin i) 8.0±1.2[3] km/s
Age 1.50[6] Gyr
ζ Hor B
Mass 1.26[5] M
Other designations
ζ Hor, CPD−55° 446, FK5 1076, HD 16920, HIP 12484, HR 802, SAO 232857[7]
Database references

Zeta Horologii (ζ Horologii, ζ Hor) is a yellow-white hued binary star system in the southern constellation of Horologium. It is visible to the naked eye with a combined apparent visual magnitude of 5.20.[2] Based upon an annual parallax shift of 20.37 mas as seen from Earth,[1] it is located around 160 light years from the Sun.

This system was determined to be a double-lined spectroscopic binary by J. H. Moore in 1911−12. The first orbital elements were published by J. Sahade and C. A. Hernández in 1964, who found it consisted of two F-type main sequence stars of probable stellar classifications F2 V and F5 V. The pair orbit each other with a period of 12.9274 days and an eccentricity of 0.25.[4] The system displays an infrared excess at a wavelength of 24μm but not at 70μm, yielding a derived temperature of 260 K. This suggests a circumbinary debris disk orbiting at a distance of less than 4.8 AU from the star system.[8]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c Corben, P. M.; Stoy, R. H. (1968), "Photoelectric Magnitudes and Colours for Bright Southern Stars", Monthly Notes of the Astronomical Society of Southern Africa, 27: 11, Bibcode:1968MNSSA..27...11C. 
  3. ^ a b c Torres, C. A. O.; et al. (December 2006), "Search for associations containing young stars (SACY). I. Sample and searching method", Astronomy and Astrophysics, 460 (3): 695–708, Bibcode:2006A&A...460..695T, arXiv:astro-ph/0609258Freely accessible, doi:10.1051/0004-6361:20065602. 
  4. ^ a b c Sahade, J.; Hernández, C. A. (February 1964), "The spectroscopic binary ζ Horologii", Annales d'Astrophysique, 27: 11, Bibcode:1964AnAp...27...11S. 
  5. ^ a b Tokovinin, A.; et al. (May 2006), "Tertiary companions to close spectroscopic binaries", Astronomy and Astrophysics, 450 (2): 681–693, Bibcode:2006A&A...450..681T, arXiv:astro-ph/0601518Freely accessible, doi:10.1051/0004-6361:20054427. 
  6. ^ a b c d Casagrande, L.; et al. (2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy & Astrophysics, 530 (A138): 21, Bibcode:2011A&A...530A.138C, arXiv:1103.4651Freely accessible, doi:10.1051/0004-6361/201016276. 
  7. ^ "zet Hor -- Spectroscopic binary", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-04-25. 
  8. ^ Trilling, D. E.; et al. (April 2007), "Debris disks in main-sequence binary systems", The Astrophysical Journal, 658 (2): 1264−1288, Bibcode:2007ApJ...658.1289T, doi:10.1086/511668.