Gamma Delphini
Gamma Delphini, Latinized from γ Delphini, is a binary star system approximately 101 light-years away in the constellation of Delphinus. The star marks one corner of the asterism "Job's Coffin". It is one of the best known double stars in the sky, consisting of a fourth magnitude orange subgiant and a fifth magnitude yellow-white dwarf.
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Delphinus |
| Right ascension | 20h 46m 38.7s |
| Declination | +16° 7′ 38″ |
| Apparent magnitude (V) | 5.14 / 4.27 |
| Characteristics | |
| Spectral type | F7V / K1IV |
| U−B color index | 0.08 / 0.97 |
| B−V color index | 0.49 / 1.04 |
| Variable type | None |
| Astrometry | |
| Radial velocity (Rv) | −7 km/s |
| Proper motion (μ) | RA: −25.88 mas/yr Dec.: −196.27 mas/yr |
| Parallax (π) | 32.14 ± 1.19 mas |
| Distance | 101 ly (31.1 pc) |
| Absolute magnitude (MV) | 2.26 / 1.81[1] |
| Orbit[2] | |
| Companion | γ1 Del |
| Period (P) | 3249 yr |
| Semi-major axis (a) | 10.22″ |
| Eccentricity (e) | 0.88 |
| Inclination (i) | 148.78° |
| Longitude of the node (Ω) | 88.06° |
| Periastron epoch (T) | 2305 |
| Argument of periastron (ω) (secondary) | 331.16° |
| Details[3] | |
| γ1 | |
| Mass | 1.57 M☉ |
| Radius | 2.21 R☉ |
| Luminosity | 6.9 L☉ |
| Temperature | 6,303 K |
| Metallicity [Fe/H] | +0.22±0.02[1] dex |
| γ2 | |
| Mass | 1.72 M☉ |
| Radius | 6.43 R☉ |
| Luminosity | 20.8 L☉ |
| Temperature | 4,865 K |
| Other designations | |
| γ1 Del: HD 197963, HIP 102531, HR 7947, SAO 106475 | |
| γ2 Del: HD 197964, HIP 102532, HR 7947/7948, SAO 106476 | |
| Database references | |
| SIMBAD | γ Del |
| γ1 Del | |
| γ2 Del | |
Stellar components
γ1 Delphini is a yellow-white dwarf star of spectral type "F7V" and an apparent magnitude of 5.14. The star is thought to be about 7 times more luminous than the Sun. γ2 Delphini is an orange subgiant star of spectral type "K1IV" and an apparent magnitude of 4.27. This star is thought to be about 20.6 times more luminous than the Sun.
Planetary system
In 1999, the presence of a planetary companion was inferred around Gamma2 Delphini, an evolved orange subgiant star.[3] Such a planet would yield a minimum mass of 0.7 Jupiter masses, orbital period of 1.44 years and separation of nearly 1.5 astronomical units (almost the orbital separation of Mars from the Sun).
The planetary candidate has not been confirmed. McDonald Observatory researches have set mass limits for potential planetary companions in orbit around the star Gamma2 Delphini.[4]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b (unconfirmed) | ≥0.7 MJ | 1.5 | 525.6 | ? | — | — |
References
- Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
- Hale, Alan (1994). "Orbital coplanarity in solar-type binary systems: Implications for planetary system formation and detection". The Astronomical Journal. 107 (1): 306–322. Bibcode:1994AJ....107..306H. doi:10.1086/116855.
- Irwin, A.W.; Vandenburg, D. A.; Larson, A. M.; et al. (1999). "Precise Stellar Radial Velocities". In J. B. Hearnshaw; C. D. Scarfe (eds.). ASP Conference Series#185. IAU Colloquium 170. Bibcode:1999ASPC..185..297I. ISBN 1-58381-011-0.
- Wittemeyer; Endl, Michael; Cochran, William D.; Hatzes, Artie P.; Walker, G. A. H.; Yang, S. L. S.; Paulson, Diane B. (2006). "Detection Limits from the McDonald Observatory Planet Search Program". The Astronomical Journal. 132 (1): 177–188. arXiv:astro-ph/0604171. Bibcode:2006AJ....132..177W. doi:10.1086/504942.
External links
- "Bright and Multiple Stars Gallery, taken at Fresno State's Campus Observatory, largely by students". California State University, Fresno. Retrieved 2008-07-02.
- "GAMMA DEL". STARS. University of Illinois. Retrieved 2017-03-29.
