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4 Aquarii (abbreviated 4 Aqr) is a binary star system in the constellation Aquarius,[9] located approximately 198 light years away from the Sun.[1] 4 Aquarii is the Flamsteed designation. It is visible to the naked eye as a dim, yellow-white hued star with a combined apparent visual magnitude of 5.99.[2] The system is moving closer to the Earth with a heliocentric radial velocity of −21.5 km/s.[5]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 20h 51m 25.74827s[1] |
| Declination | −05° 37′ 35.8719″[1] |
| Apparent magnitude (V) | 5.99[2] (6.40 + 7.43)[3] |
| Characteristics | |
| Spectral type | F7 IV + F6: V:[4] |
| B−V color index | 0.464±0.003[2] |
| Astrometry | |
| Radial velocity (Rv) | −21.50[5] km/s |
| Proper motion (μ) | RA: 95.47[1] mas/yr Dec.: 1.78[1] mas/yr |
| Parallax (π) | 16.47 ± 0.59 mas[1] |
| Distance | 198 ± 7 ly (61 ± 2 pc) |
| Absolute magnitude (MV) | 2.15[6] |
| Orbit[7] | |
| Period (P) | 200.7±1.1 yr |
| Semi-major axis (a) | 0.816±0.006″ |
| Eccentricity (e) | 0.535+0.006 −0.005 |
| Inclination (i) | 64.06+0.26 −0.27° |
| Longitude of the node (Ω) | 174.31+0.38 −0.39° |
| Periastron epoch (T) | B 1,896.8+0.39 −0.40 |
| Argument of periastron (ω) (secondary) | 45.9±1.2° |
| Details[6] | |
| 4 Aqr A | |
| Mass | 1.618±0.004[7] M☉ |
| Luminosity | 11.0 L☉ |
| Surface gravity (log g) | 3.79 cgs |
| Temperature | 6,440 K |
| Metallicity [Fe/H] | 0.18[8] dex |
| Rotational velocity (v sin i) | 34.6 km/s |
| Age | 1.60[8] Gyr |
| 4 Aqr B | |
| Mass | 1.331±0.003[7] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | 4 Aqr |
| 4 Aqr A | |
| 4 Aqr B | |
This is a visual binary with an orbital period of 200.7 years and an eccentricity of 0.535.[7] The magnitude 6.40[3] primary, designated component A, is an F-type subgiant star with a stellar classification of F7 IV,[4] suggesting that it has exhausted the hydrogen at its core and evolved off the main sequence.[7] It has a dynamically-measured mass 1.6[7] times that of the Sun and is radiating 11 times the Sun's luminosity from its photosphere at an effective temperature of 6,440 K.[6] The magnitude 7.43[3] secondary, component B, is a suspected F-type main-sequence star of class F6 V.[4] The pair are an estimated 1.6 billion years old.[8]
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