Psi1 Draconis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco |
| ψ1 Dra A | |
| Right ascension | 17h 41m 56.35536s |
| Declination | +72° 08′ 55.8481″ |
| Apparent magnitude (V) | 4.58 |
| ψ1 Dra B | |
| Right ascension | 17h 41m 58.10460s |
| Declination | +72° 09′ 24.8581″ |
| Apparent magnitude (V) | 5.82 |
| Characteristics | |
| ψ1 Dra A | |
| Spectral type | F5IV-V |
| U−B color index | +0.01 |
| B−V color index | +0.43 |
| ψ1 Dra B | |
| Spectral type | F8V |
| U−B color index | +0.04 |
| B−V color index | +0.525 |
| Astrometry | |
| ψ1 Dra A | |
| Radial velocity (Rv) | −13.30±0.2 km/s |
| Proper motion (μ) | RA: +25.32 mas/yr Dec.: −268.47 mas/yr |
| Parallax (π) | 43.79±0.45 mas |
| Distance | 74.5 ± 0.8 ly (22.8 ± 0.2 pc) |
| ψ1 Dra B | |
| Radial velocity (Rv) | −11.20±0.3 km/s |
| Proper motion (μ) | RA: +34.89 mas/yr Dec.: −275.94 mas/yr |
| Parallax (π) | 43.36 ± 0.51 mas |
| Distance | 75.2 ± 0.9 ly (23.1 ± 0.3 pc) |
| Orbit | |
| Primary | ψ1 Dra Aa |
| Companion | ψ1 Dra Ab |
| Period (P) | 6774+271 −167 d |
| Semi-major axis (a) | 9.1+0.4 −0.3 AU |
| Eccentricity (e) | 0.679+0.006 −0.004 |
| Inclination (i) | 31±1° |
| Periastron epoch (T) | 2450388+169 −273 |
| Argument of periastron (ω) (secondary) | 32.6±0.7° |
| Semi-amplitude (K1) (primary) | 5.18+0.04 −0.03 km/s |
| Semi-amplitude (K2) (secondary) | 11.1±0.2 km/s |
| Details | |
| ψ1 Dra A | |
| Mass | 1.38+0.15 −0.08 / 0.70±0.07 M☉ |
| Radius | 1.2–1.3 R☉ |
| Surface gravity (log g) | 3.90±0.11 cgs |
| Temperature | 6,544±42 / 4,400±300 K |
| Metallicity [Fe/H] | −0.10±0.05 dex |
| ψ1 Dra B | |
| Mass | 1.19±0.07 M☉ |
| Radius | 1.5 R☉ |
| Surface gravity (log g) | 4.20±0.12 cgs |
| Temperature | 6,212±75 K |
| Age | 3.3±1.0 Gyr |
| Other designations | |
| Dziban, 31 Dra, ADS 10759 AB, Gliese 694.1 | |
| ψ1 Dra A: BD+72°804, HD 162003, HIP 86614, HR 6636, SAO 8890 | |
| ψ1 Dra B: BD+72°805, HD 162004, HIP 86620, HR 6637, SAO 8891 | |
| Database references | |
| SIMBAD | ψ1 Dra AB |
| ψ1 Dra A | |
| ψ1 Dra B | |
| Exoplanet Archive | data |
Psi1 Draconis (ψ1 Draconis, abbreviated Psi1 Dra, ψ1 Dra), also designated 31 Draconis, is a triple star system in the northern constellation of Draco. The system is fairly close, and is located about 75 light-years (23 parsecs) from the Sun, based on its parallax.
Psi1 Draconis was considered a binary star consisting of an F-type subgiant and an F-type main-sequence star, designated Psi1 Draconis A (officially named Dziban /ˈzaɪbən/, from the traditional name of the system) and Psi1 Draconis B, respectively. In 2015, Psi1 Draconis A was itself found to be a double-lined spectroscopic binary, making the system a triple. The companion to Psi1 Draconis A was designated Psi1 Draconis C by its discoverers.
Also in 2015, Psi1 Draconis B was discovered to be orbited by an exoplanet, designated Psi1 Draconis Bb.