 | |
| Discovery | |
|---|---|
| Discovered by | Vogt et al. |
| Discovery site |  United States |
| Discovery date | June 24, 2005 |
| Doppler spectroscopy | |
| Orbital characteristics | |
| 6.074±0.080AU | |
| Eccentricity | 0.3848±0.0086[1] |
| 5189±21[1]d | |
| 2450770±16[1] | |
| 206.3±1.7[1] | |
| Semi-amplitude | 53.41±0.75[1] |
| Star | HD 217107 |
HD 217107 c is anextrasolar planet[2] approximately 64light-years away from Earth in theconstellation ofPisces (theFish). The planet was the second planet to be discovered orbiting the starHD 217107. HD 217107 c's existence was hypothesized in 1998 due to the eccentricity of the inner planet's orbit and confirmed in 2005 when radial velocity studies of the star indicated another, more distant and massive companion orbiting the star. The planet has an eccentric orbit lasting on order of a decade.
A study of theradial velocity of HD 217107 carried out in 1998 revealed that its motion along the line of sight varied over a 7.1 day cycle, indicating the presence of a planet in orbit around the star. The planet was designatedHD 217107 b, and was found to be somewhat heavier thanJupiter, and orbiting extremely close to the parent star in an orbit with quite a largeeccentricity.[3]
Most planets with orbital periods of less than 10 days have almost circular orbits, and its discoverers proposed that the high eccentricity of HD 217107 b's orbit could be due to the gravitational influence of a second planet in the system at a distance of severalastronomical units (AU).[4] Confirmation of the existence of the second planet followed in 2005, and it was designated HD 217107 c.
The parameters of this planet was initially very weakly constrained, with a period in excess of 8 years with a high eccentricity and a minimum mass of approximately two times the mass of Jupiter. Continued observations restrained the plausible solutions substantially, resulting in the current parameters published in 2008.[5]
