Phi Herculis
Star in the constellation Hercules
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Phi Herculis (Ï Her) is a binary star[4] system in the northern constellation of Hercules. Based upon an annual parallax shift of 15.99 mas as seen from Earth,[1] it is located around 204 light years from the Sun. With a combined apparent visual magnitude of 4.24,[2] it is bright enough to be seen with the naked eye.
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hercules |
| Right ascension | 16h 08m 46.17745s[1] |
| Declination | +44° 56â² 05.6663â³[1] |
| Apparent magnitude (V) | 4.24[2] |
| Characteristics | |
| Spectral type | B9VspHgMn[3] + A8V[4] |
| UâB color index | â0.23[2] |
| BâV color index | â0.06[2] |
| Variable type | α2 CVn?[5] |
| Astrometry | |
| Radial velocity (Rv) | â16.3±0.4[6] km/s |
| Proper motion (μ) | RA: â26.63[1] mas/yr Dec.: +36.76[1] mas/yr |
| Parallax (Ï) | 15.99±0.45 mas[1] |
| Distance | 204 ± 6 ly (63 ± 2 pc) |
| Absolute magnitude (MV) | A: 0.100 ± 0.059 B: 2.670 ± 0.074[7] |
| Orbit[7] | |
| Period (P) | 564.834±0.038 d |
| Semi-major axis (a) | 32.027±0.028 mas |
| Eccentricity (e) | 0.52614±0.00086 |
| Inclination (i) | 9.1±0.4° |
| Longitude of the node (Ω) | 190.4±1.4° |
| Periastron epoch (T) | 2450121.43 ± 0.20 JD |
| Argument of periastron (Ï) (secondary) | 350.3±1.4° |
| Semi-amplitude (K1) (primary) | 2.772±0.073 km/s |
| Semi-amplitude (K2) (secondary) | 8.1[4] km/s |
| Details | |
| Ï Her A | |
| Mass | 3.05±0.24[7] Mâ |
| Luminosity | 72[8] Lâ |
| Surface gravity (log g) | 4.05±0.15[4] cgs |
| Temperature | 11,525±150[4] K |
| Metallicity [Fe/H] | â0.03[7] dex |
| Rotational velocity (v sin i) | 8.0±1.0[4] km/s |
| Age | 210[7] Myr |
| Ï Her B | |
| Mass | 1.614±0.066[7] Mâ |
| Surface gravity (log g) | 4.30±0.15[4] cgs |
| Temperature | 8,000±150[4] K |
| Rotational velocity (v sin i) | 50.0±3.0[4] km/s |
| Other designations | |
| Ï Her, 11 Her, BD+45°2376, FK5 601, HD 145389, HIP 79101, HR 6023, SAO 45911.[9] | |
| Database references | |
| SIMBAD | data |
This is a single-lined spectroscopic binary star system with an orbital period of 564.8 days and an eccentricity of 0.526.[7] The primary, component A, is a B-type main sequence star with a stellar classification of B9VspHgMn.[3] It is a chemically peculiar star of the type called a mercury-manganese star.[4] The star is tentatively catalogued as an Alpha2 Canum Venaticorum variable, with brightness variations of just 0.01 magnitudes.[5][12]
The secondary, component B, was first separated via interferometry in 2004.[13] It is an A-type main sequence star of class A8V.[4] The magnitude difference between the two components is 2.64.[13]