Theta Antliae
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Antlia |
| Right ascension | 09h 44m 12.09512s |
| Declination | −27° 46′ 10.1011″ |
| Apparent magnitude (V) | 4.79 |
| Characteristics | |
| Spectral type | A8 Vm + G7 III |
| U−B color index | +0.35 |
| B−V color index | +0.50 |
| Astrometry | |
| Radial velocity (Rv) | +24.0 km/s |
| Proper motion (μ) | RA: −53.23 mas/yr Dec.: +37.24 mas/yr |
| Parallax (π) | 9.61±0.46 mas |
| Distance | 340 ± 20 ly (104 ± 5 pc) |
| Absolute magnitude (MV) | −0.30 |
| Orbit | |
| Companion | θ Ant B |
| Period (P) | 18.266±0.185 yr |
| Semi-major axis (a) | 0.110±0.002″ |
| Eccentricity (e) | 0.404±0.005 |
| Inclination (i) | 123.6±1.0° |
| Longitude of the node (Ω) | 3.5±1.0° |
| Periastron epoch (T) | 2020.143±0.200 |
| Argument of periastron (ω) (secondary) | 141.2±3.0° |
| Details | |
| θ Ant A | |
| Mass | 1.8±0.1 M☉ |
| θ Ant B | |
| Mass | 2.1±0.5 M☉ |
| Other designations | |
| θ Antliae, Tet Ant, θ Ant, CD−27 6881, FK5 366, HD 84367, HIP 47758, HR 3871, SAO 177908, PPM 256646 | |
| Database references | |
| SIMBAD | data |
Theta Antliae is a binary star system in the southern constellation of Antlia. Its identifier is a Bayer designation that was Latinized from θ Antliae, and is abbreviated Tet Ant or θ Ant, respectively. The pair have a combined apparent visual magnitude of +4.78, which is bright enough to be faintly visible to the naked eye. The brighter component is magnitude +5.30 while the secondary is +6.18. Based upon parallax measurements, it is located at a distance of around 340 light-years (104 parsecs) from Earth. The system is receding with a heliocentric radial velocity of +24 km/s.
The binary nature of this system was discovered by W. S. Finsen in 1952. The primary component of this system, θ Antliae A, has a stellar classification of A8 Vm, indicating that it is an A-type main sequence star with enhanced metallic lines in its spectrum. The companion, θ Antliae B, is a giant star with a classification of G7 III. The pair have an orbital period of 18.3 years, a significant eccentricity of 0.4, and an angular separation of 0.1 arcseconds.