Zeta Aquarii
 Location of ζ Aquarii (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 28m 49.90685s |
| Declination | –00° 01′ 11.7942″ |
| Apparent magnitude (V) | 3.65 (4.42 / 4.51) |
| Characteristics | |
| Spectral type | F3 V + F6 IV |
| U−B color index | –0.01 |
| B−V color index | +0.40 |
| Astrometry | |
| Radial velocity (Rv) | +24.9/+28.9 km/s |
| Proper motion (μ) |
RA: +182.92 mas/yr Dec.: +50.36 mas/yr |
| Parallax (π) | 35.50 ± 1.26mas |
| Distance | 92 ± 3 ly (28.2 ± 1.0 pc) |
| Absolute magnitude (MV) | 1.15 |
| Orbit | |
| Primary | ζ Aqr Aa |
| Companion | ζ Aqr Ab |
| Period (P) | 25.95 ± 0.048 yr |
| Semi-major axis (a) | 0.385″ |
| Eccentricity (e) | 0.872 ± 0.006 |
| Inclination (i) | 11.8 ± 6.7° |
| Longitude of the node (Ω) | 293.7 ± 74° |
| Periastron epoch (T) | B 2006.52 ± 0.13 |
|
Argument of periastron (ω) (secondary) |
100.9 ± 73° |
| Orbit | |
| Primary | ζ Aqr A |
| Companion | ζ Aqr B |
| Period (P) | 540 ± 15 yr |
| Semi-major axis (a) | 3.496 ± 0.046″ |
| Eccentricity (e) | 0.419 ± 0.011 |
| Inclination (i) | 142.0 ± 0.4° |
| Longitude of the node (Ω) | 131.3 ± 0.8° |
| Periastron epoch (T) | B 1981.50 ± 0.58 |
|
Argument of periastron (ω) (secondary) |
269.3 ± 1.7° |
| Details | |
| ζ Aqr A | |
| Mass | 1.4 / 0.6 M☉ |
| Metallicity [Fe/H] | –0.13 dex |
| Rotational velocity (v sin i) | 62 km/s |
| Age | 1.0 Gyr |
| ζ Aqr B | |
| Mass | 1.4 M☉ |
| Rotational velocity (v sin i) | 56 km/s |
| Other designations | |
| ζ Aqr A: ζ2 Aquarii, Zeta2 Aquarii, HD 213052, HR 8559, SAO 146108. | |
| ζ Aqr B: ζ1 Aquarii, Zeta1 Aquarii, HD 213051, HR 8558, SAO 146107. | |
| Database references | |
| SIMBAD | data |
Zeta Aquarii (ζ Aquarii, ζ Aqr) is the Bayer designation for a binary, or possibly a triple star system; the central star of the "water jar" asterism in the equatorial constellation of Aquarius. The combined apparent visual magnitude of this system is 3.65, which is readily visible to the naked eye. Parallax measurements yield a distance estimate of around 92 light-years (28 parsecs) from Earth.
Zeta Aquarii has the traditional name Sadaltager (or Altager), from the Arabic سعد التاجر (sa‘d al-tājir), meaning "luck of the merchant". In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Achr al Achbiya (أجر ألأجبية - akhir al ahbiyah), which was translated into Latin as Postrema Tabernaculorum, meaning the end of luck of the homes (tents). This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and η Aqr (Hydria), were al Aḣbiyah (الأخبية), the Tent.
In Chinese, 墳墓 (Fén Mù), meaning Tomb, refers to an asterism consisting of ζ Aquarii, γ Aquarii, η Aquarii and π Aquarii. Consequently, ζ Aquarii itself is known as 墳墓一 (Fén Mù yī, English: the First Star of Tomb.)
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