Phi Cygni
Star in the constellation Cygnus
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Phi Cygni, Latinized from φ Cygni, is a binary star[12] system in the northern constellation of Cygnus. It is faintly visible to the naked eye with an apparent visual magnitude of 4.70.[2] The annual parallax shift is 14.92 mas[6] as measured from Earth, which yields a distance estimate of around 220 light years. It is moving further from the Sun with a radial velocity of +4.5 km/s.[7]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 39m 22.60591s[1] |
| Declination | +30° 09′ 11.9604″[1] |
| Apparent magnitude (V) | 4.70[2] (5.31 + 5.6)[3] |
| Characteristics | |
| Evolutionary stage | red clump[4][5] |
| Spectral type | G8III + G8III[6] |
| U−B color index | +0.81[2] |
| B−V color index | +0.98[2] |
| Astrometry | |
| Radial velocity (Rv) | +4.50[7] km/s |
| Proper motion (μ) | RA: +2.48 mas/yr[1] Dec.: +36.50 mas/yr[1] |
| Parallax (π) | 14.9244±0.4176 mas[6] |
| Distance | 219 ± 6 ly (67 ± 2 pc) |
| Absolute magnitude (MV) | +0.12[8] (+0.77/+1.07)[9] |
| Orbit | |
| Period (P) | 434.208[10] days |
| Semi-major axis (a) | 26.9[3] mas″ |
| Eccentricity (e) | 0.5557[10] |
| Inclination (i) | 80.8[3]° |
| Longitude of the node (Ω) | 251[3]° |
| Periastron epoch (T) | 2451239.58[10] |
| Argument of periastron (ω) (secondary) | 209.41[10]° |
| Semi-amplitude (K1) (primary) | 26.40[10] km/s |
| Semi-amplitude (K2) (secondary) | 27.22[10] km/s |
| Details[6] | |
| A | |
| Mass | 2.104±0.049 M☉ |
| Radius | 7.46[a] R☉ |
| Luminosity | 34.7+2.5 −2.3 L☉ |
| Temperature | 5,130±120 K |
| Metallicity [Fe/H] | −0.11[10] dex |
| Rotational velocity (v sin i) | 4.7[10] km/s |
| Age | 479+58 −52 Myr |
| B | |
| Mass | 2.040±0.042 M☉ |
| Radius | 7.04[b] R☉ |
| Luminosity | 28±3 L☉ |
| Temperature | 5,010 K |
| Rotational velocity (v sin i) | 4.8[10] km/s |
| Age | 562+69 −61 Myr |
| Other designations | |
| φ Cygni, 12 Cygni, BD+29°3684, GC 27203, HD 185734, HIP 96683, HR 7478, SAO 68637, WDS J19394+3009AB[11] | |
| Database references | |
| SIMBAD | data |
φ Cygni is a double-lined spectroscopic binary system, which means that the absorption lines of both components are visible in the spectrum. The two sets of spectral lines are almost identical and both stars are assigned a spectral type of K0III, meaning they have evolved into giants. They are considered to be red clump giants, stars that have begun core helium fusion and lie on the horizontal branch but because of their metallicity and the size of their hydrogen envelope they are found very close to the red giant branch.[4][5] The two stars are assumed to have the same age, which would be around 650 million years.[13][9] The pair have an orbital period of 434.208 days, or 1.2 Earth years, a semimajor axis of 26.9 mas, and a high eccentricity of 0.56.[10]
Notes
- Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K:
- Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K:
