Alpha Delphini
Alpha Delphini (α Delphini, abbreviated Alpha Del, α Del) is a multiple star system in the constellation of Delphinus.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Delphinus |
| Right ascension | 20h 39m 38.28720s |
| Declination | +15° 54′ 43.4637″ |
| Apparent magnitude (V) | +3.777 (3.86 + 6.43) |
| Characteristics | |
| Spectral type | B9 IV |
| U−B color index | −0.205 |
| B−V color index | −0.061 |
| Astrometry | |
| Radial velocity (Rv) | −3.40 km/s |
| Proper motion (μ) | RA: 53.82 ± 0.43 mas/yr Dec.: 8.47 ± 0.31 mas/yr |
| Parallax (π) | 12.85 ± 0.44 mas |
| Distance | 254 ± 9 ly (78 ± 3 pc) |
| Absolute magnitude (MV) | −0.4 |
| Orbit | |
| Primary | Aa (A) |
| Companion | Ab (B) |
| Period (P) | 6175.3±3.2 d |
| Semi-major axis (a) | 0.15809±0.00013" (12.7±0.4 AU) |
| Eccentricity (e) | 0.4615±0.0016 |
| Inclination (i) | 161.01±0.30° |
| Longitude of the node (Ω) | 120.62±1.19° |
| Periastron epoch (T) | JD57988.7 |
| Argument of periastron (ω) (secondary) | 91.73±1.09° |
| Orbit | |
| Primary | Ab1 (Ba) |
| Companion | Ab2 (Bb) |
| Period (P) | 29.9873±0.0021 d |
| Semi-major axis (a) | 0.0003587±0.000010" (0.281±0.008 AU) |
| Eccentricity (e) | 0.0761±0.0012 |
| Inclination (i) | 22.11±0.61° |
| Longitude of the node (Ω) | 359.97±0.65° |
| Periastron epoch (T) | JD58762.84 |
| Argument of periastron (ω) (secondary) | 166.43±1.27° |
| Semi-amplitude (K2) (secondary) | 21.19±0.18 km/s |
| Details | |
| Aa (A) | |
| Mass | 3.83±0.33 M☉ |
| Radius | 3.92 R☉ |
| Surface gravity (log g) | 3.93 cgs |
| Temperature | 11,643 K |
| Rotational velocity (v sin i) | 144 km/s |
| Age | 227 Myr |
| Ab1 (Ba) | |
| Mass | 1.82±0.15 M☉ |
| Ab2 (Bb) | |
| Mass | 1.49±0.12 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
It consists of a triple star, designated Alpha Delphini A, together with five faint, probably optical companions, designated Alpha Delphini B, C, D, E and F. A's two components are themselves designated Alpha Delphini Aa (officially named Sualocin /ˈswɒloʊsɪn/, the historical name for the entire system) and Ab.
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