Theta Antliae

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Theta Antliae
Diagram showing star positions and boundaries of the Antlia constellation and its surroundings
Cercle rouge 100%.svg

Location of θ Antliae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Antlia
Right ascension 09h 44m 12.09512s[1]
Declination –27° 46′ 10.1011″[1]
Apparent magnitude (V) 4.79[2]
Spectral type A8 Vm + G7 III[3]
U−B color index +0.35[2]
B−V color index +0.50[2]
Radial velocity (Rv) +24.0[4] km/s
Proper motion (μ) RA: –53.23[1] mas/yr
Dec.: +37.24[1] mas/yr
Parallax (π) 9.61 ± 0.46[1] mas
Distance 340 ± 20 ly
(104 ± 5 pc)
Companion θ Antliae B
Period (P) 18.32 yr
Semi-major axis (a) 0.134"
Eccentricity (e) 0.445
Inclination (i) 124°
Longitude of the node (Ω) 176.8°
Periastron epoch (T) 1965.75
Other designations
CD–27 6881, HIP 47758, FK5 366, HD 84367, HR 3871, SAO 177908.[6]
Database references

Theta Antliae (θ Ant, θ Antliae) is the Bayer designation for a binary star in the southern constellation of Antlia. The pair have a combined apparent visual magnitude of +4.78;[2] the brighter component is magnitude +5.30 while the secondary is +6.18.[7] Based upon parallax measurements, it is located at a distance of around 340 light-years (100 parsecs) from Earth.

The primary component of this system, θ Ant A, has a stellar classification of A8 Vm,[3] indicating that it is an A-type main sequence star with enhanced metallic lines in its spectrum. The companion, θ Ant B, is a giant star with a classification of G7 III.[3] The pair have an orbital period of 18.3 years, a significant eccentricity of 0.445, and they have an angular separation of 0.1 arcseconds.[5]


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J. 
  3. ^ a b c Ginestet, N.; Carquillat, J. M. (December 2002), "Spectral Classification of the Hot Components of a Large Sample of Stars with Composite Spectra, and Implication for the Absolute Magnitudes of the Cool Supergiant Components", The Astrophysical Journal Supplement Series, 143 (2): 513–537, Bibcode:2002ApJS..143..513G, doi:10.1086/342942. 
  4. ^ Wilson, Ralph Elmer (1953), General catalogue of stellar radial velocities, Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W. 
  5. ^ a b Heintz, W. D. (March 1982), "Orbits of 16 visual binaries", Astronomy and Astrophysics Supplement Series, 47: 569–573, Bibcode:1982A&AS...47..569H. 
  6. ^ "tet Ant -- Star in double system", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-06-28. 
  7. ^ 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:0806.2878Freely accessible, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x. 

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