 ψ1 Draconis in optical light | |
| Observation data EpochJ2000 EquinoxJ2000 | |
|---|---|
| Constellation | Draco |
| ψ1 Dra A | |
| Right ascension | 17h 41m 56.35536s[1] |
| Declination | +72° 08′ 55.8481″[1] |
| Apparent magnitude (V) | 4.58[2] |
| ψ1 Dra B | |
| Right ascension | 17h 41m 58.10460s[1] |
| Declination | +72° 09′ 24.8581″[1] |
| Apparent magnitude (V) | 5.82[3] |
| Characteristics | |
| ψ1 Dra A | |
| Spectral type | F5IV-V[4] |
| U−Bcolor index | +0.01[2] |
| B−Vcolor index | +0.43[2] |
| ψ1 Dra B | |
| Spectral type | F8V[5] |
| U−Bcolor index | +0.04[2] |
| B−Vcolor index | +0.525[2] |
| Astrometry | |
| ψ1 Dra A | |
| Radial velocity (Rv) | -13.30 ± 0.2[6] km/s |
| Proper motion (μ) | RA: 25.32[1]mas/yr Dec.: -268.47[1]mas/yr |
| Parallax (π) | 43.79±0.45 mas[1] |
| Distance | 74.5 ± 0.8 ly (22.8 ± 0.2 pc) |
| ψ1 Dra B | |
| Radial velocity (Rv) | -11.20 ± 0.3[6] km/s |
| Proper motion (μ) | RA: 34.89[1] mas/yr Dec.: -275.94[1] mas/yr |
| Parallax (π) | 43.36 ± 0.51 mas[1] |
| Distance | 75.2 ± 0.9 ly (23.1 ± 0.3 pc) |
| Orbit[7] | |
| Primary | ψ1 Dra Aa |
| Companion | ψ1 Dra Ab |
| Period (P) | 6774+271 −167 d |
| Semi-major axis (a) | 9.1+0.4 −0.3AU |
| Eccentricity (e) | 0.679+0.006 −0.004 |
| Inclination (i) | 31 ± 1° |
| Periastronepoch (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[7] M☉ |
| Radius | 1.2–1.3[8] R☉ |
| Surface gravity (log g) | 3.90 ± 0.11[9] cgs |
| Temperature | 6544 ± 42 / 4400 ± 300[7] K |
| Metallicity [Fe/H] | −0.10 ± 0.05[9] dex |
| ψ1 Dra B | |
| Mass | 1.19 ± 0.07[9] M☉ |
| Radius | 1.5[8] R☉ |
| Surface gravity (log g) | 4.20 ± 0.12[9] cgs |
| Temperature | 6212 ± 75[9] K |
| Age | 3.3 ± 1.0 G[9] years |
| 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[4] | |
| ψ1 Dra B:BD+72° 805,HD 162004,HIP 86620,HR 6637,SAO 8891[5] | |
| Database references | |
| SIMBAD | ψ1 Dra AB |
| ψ1 Dra A | |
| ψ1 Dra B | |
Psi1 Draconis (ψ1 Draconis, abbreviatedPsi1 Dra,ψ1 Dra), also designated31 Draconis, is atriple star system in the northernconstellation ofDraco. The system is fairly close, and is located about 75light-years (23parsecs) from theSun, based on itsparallax.[1]
Psi1 Draconis was considered abinary star consisting of anF-typesubgiant and anF-type main-sequence star, designated Psi1 Draconis A (officially namedDziban/ˈzaɪbən/, from the traditional name of the system)[10] and Psi1 Draconis B, respectively. In 2015, Psi1 Draconis A was itself found to be a double-linedspectroscopic binary, making the system a triple. The companion to Psi1 Draconis A was designated Psi1 Draconis C by its discoverers.[7]
Also in 2015, Psi1 Draconis B was discovered to be orbited by anexoplanet, designated Psi1 Draconis Bb.[9]
ψ1 Draconis (Latinised toPsi1 Draconis) is the system'sBayer designation and31 Draconis itsFlamsteed designation. The designation of the components –ψ1 Draconis A andB – derives from the convention used by the Washington Multiplicity Catalog (WMC) formultiple star systems, and adopted by theInternational Astronomical Union (IAU).[11]
Psi1 Draconis bore the traditional name ofDziban orDsiban, derived from theArabic Adh-Dhi'ban, meaning "The two wolves" or "The two jackals".[12] In 2016, the IAU organized aWorking Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entiremultiple systems.[14] It approved the nameDziban for the component Psi1 Draconis A on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[10]
InChinese astronomy, Psi1 Draconis is called 女史,Pinyin: Nǚshǐ, meaningFemale Protocol, because this star is marking itself and stands alone in theasterismFemale Protocol in thePurple Forbidden enclosure (seeChinese constellation).[15] 女史 (Nǚshǐ) has been Latinised intoNiu She by R.H. Allen, meaning "the Palace Governess", or "a Literary Woman".[12]
ψ1 Draconis AC and ψ1 Draconis B are separated by about 31 arcseconds. Only a very small fraction of the orbit has been observed: anorbital period of 10,000 years has been calculated,[16] but it is extremely preliminary and likely to be in high error.
ψ1 Draconis A and C have varyingradial velocities in respect to Earth, indicating that there must be orbital motion. The orbital period is estimated to be around 20 years, and theeccentricity must be fairly high, around 0.679.[7]
Psi1 Draconis Bb is aJupiter-likeexoplanet orbiting Psi1 Draconis B, the secondary star. The planet was discovered when periodicDoppler shifts in the star'sspectrum revealed the presence of a planet, similar to the spectroscopic binary nature of Psi1 Draconis AC. Itsminimum mass is1.53 MJ, and it orbits its host star every 8.5 years taking a relatively eccentric orbit.[9]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥1.53 ± 0.10 MJ | 4.43 ± 0.04 | 3117 ± 42s | 0.40 ± 0.05 | — | — |
