HD 17156 c

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HD 17156 c
Exoplanet List of exoplanets
Parent star
Star HD 17156
Constellation Cassiopeia
Right ascension (α) 02h 49m 04.49s
Declination (δ) +71° 45′ 11.64″
Apparent magnitude (mV) 8.17
Distance 255.19 ly
(78.24 pc)
Spectral type G0
Mass (m) 1.24 ± 0.03 M
Radius (r) 1.446+0.099
Temperature (T) 6079 ± 80 K
Metallicity [Fe/H] 0.24 ± 0.05
Age 3.06+0.64
Orbital elements
Semi-major axis (a) 0.481±0.001 AU
Eccentricity (e) 0.136±0.005
Orbital period (P) 111.314±3 d
Physical characteristics
Mass (m) 0.063 ± 0.007 MJ
(20 ± 2.2 M)
Discovery information
Discovery date 20 March 2008
Discoverer(s) Short et al.
Discovery method Planetary perturbation
Discovery site  United States
Discovery status Unconfirmed
Database references
Extrasolar Planets
Exoplanet Archive data
Open Exoplanet Catalogue data

HD 17156 c is a plausible extrasolar planet approximately 255 light-years away in the constellation of Cassiopeia. The planet is thought to be orbiting the yellow giant star HD 17156. This planet has a mass of 0.063 Jupiter mass (or 20 Earth masses) and takes about 111.314 days or 0.305 year to orbit the star, classifying the planet as a cool Neptunian planet. This put it in the distance of 0.481 astronomical units or 72.0 gigameters with a moderate eccentricity.

The two planets "exchange angular momentum in a 5:1 mean motion resonance".

This planet was discovered on the vernal equinox of 2008 by analyzing perturbations with the inner planet HD 17156 b. The paper was submitted to Astrophysical Journal Letters 20 March and revised 14 June.

See also[edit]


  • Donald Short; William F. Welsh; Jerome A. Orosz; Gur Windmiller (2008). "Orbital Dynamics Of A Second Planet In HD17156". arXiv:0803.2935. 

Coordinates: Sky map 02h 49m 44.49s, +71° 45′ 11.64″