Theta Capricorni
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Capricornus |
| Right ascension | 21h 05m 56.82783s |
| Declination | −17° 13′ 58.3021″ |
| Apparent magnitude (V) | +4.07 |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | A1 V |
| U−B color index | +0.01 |
| B−V color index | −0.01 |
| Astrometry | |
| Radial velocity (Rv) | −10.9 km/s |
| Proper motion (μ) | RA: +79.33 mas/yr Dec.: −62.01 mas/yr |
| Parallax (π) | 20.11±0.28 mas |
| Distance | 162 ± 2 ly (49.7 ± 0.7 pc) |
| Absolute magnitude (MV) | +0.60 |
| Orbit | |
| Primary | A |
| Name | B |
| Period (P) | 143 days |
| Semi-major axis (a) | 0.78 AU |
| Details | |
| A | |
| Mass | 2.54 M☉ |
| Radius | 2.35 R☉ |
| Luminosity | 65 L☉ |
| Surface gravity (log g) | 4.19±0.14 cgs |
| Temperature | 10,221 K |
| Metallicity [Fe/H] | +0.26 dex |
| Rotational velocity (v sin i) | 104 km/s |
| Age | 280 Myr |
| B | |
| Mass | 0.56 M☉ |
| Radius | 0.52 R☉ |
| Temperature | 3,900 K |
| Age | 280 Myr |
| Other designations | |
| Udang, Dorsum, θ Cap, 23 Cap, BD−17°6174, FK5 1552, HD 200761, HIP 104139, HR 8075, SAO 164132 | |
| Database references | |
| SIMBAD | data |
Theta Capricorni, Latinized from θ Capricorni, (Theta Cap or θ Cap) formally named Udang, is a binary star system in the southern constellation of Capricornus, positioned 0.58° south of the ecliptic. It can be seen with the naked eye, having an apparent visual magnitude of +4.07. Based upon an annual parallax shift of 20.11 mas as seen from the Earth, the star is about 162 light-years (50 pc) from the Sun. It is drifting closer with a radial velocity of −11 km/s.
The star or star system is almost eclipsed by the Sun on about 3 February, when it will figure behind the Sun's corona if there is a full solar eclipse. Thus the star can be viewed the whole night, crossing the sky, in early August (in the current epoch). It can be occulted by the Moon.