Gamma Delphini

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γ Delphini
Delphinus constellation map.svg
Red circle.svg
Location of γ Delphini (circled)
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
Spectral type F7V / K1IV
U−B color index 0.08 / 0.97
B−V color index 0.49 / 1.04
Variable type None
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
Distance101 ly
(31.1 pc)
Absolute magnitude (MV)2.26 / 1.81[1]
Companionγ1 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)
Mass1.57 M
Radius2.21 R
Luminosity6.9 L
Temperature6,303 K
Metallicity [Fe/H]+0.22±0.02[1] dex
Mass1.72 M
Radius6.43 R
Luminosity20.8 L
Temperature4,865 K
Other designations
γ Del, 12 Delphini, BD+15°4255, CCDM J20467+1607, WDS 20467+1607
γ1 Del: HD 197963, HIP 102531, HR 7947, SAO 106475
γ2 Del: HD 197964, HIP 102532, HR 7947/7948, SAO 106476
Database references
γ1 Del
γ2 Del

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.

Stellar components[edit]

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[edit]

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]

The Gamma Delphini planetary system[3]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b (unconfirmed) ≥0.7 MJ 1.5 525.6 ?


  1. ^ a b 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.
  2. ^ 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.
  3. ^ a b c 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.
  4. ^ 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[edit]