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HD 217107 c
Extrasolar planet List of extrasolar planets
Parent star

<tr> <td colspan="2">Star</td> <td>HD 217107</td></tr><tr> <td colspan="2">Constellation</td> <td>Pisces</td></tr><tr> <td>Right ascension</td> <td style="text-align: center">(α)</td> <td>22h 58m 15.54s</td></tr><tr> <td>Declination</td> <td style="text-align: center">(δ)</td> <td>−2° 23′ 43.39″</td></tr><tr><td colspan="2">Distance</td><td>64.3 ± 1 ly
(19.7 ± 0.3 pc)</td></tr><tr><td colspan="2">Spectral type</td> <td>G8IV</td></tr>

Orbital elements

<tr><td>Semimajor axis</td><td style="text-align: center">(a)</td> <td>5.27 ± 0.36 AU</td></tr><tr> <td>Eccentricity</td> <td style="text-align: center">(e)</td> <td>0.517 ± 0.033</td></tr><tr><td>Orbital period</td><td style="text-align: center">(P)</td> <td>4210 ± 190 d</td></tr><tr> <td>Argument of
periastron
</td> <td style="text-align: center">(ω)</td> <td>198.6 ± 6°</td></tr><tr> <td>Semi-amplitude</td> <td style="text-align: center">(K)</td> <td>35.7 ± 1.3 m/s</td></tr>

Physical characteristics

<tr><td>Mass</td><td style="text-align: center">(m)</td><td>≥2.49 ± 0.25 MJ</td></tr>

Discovery information

<tr> <td colspan="2">Discovery date</td> <td>June 24, 2005</td></tr><tr> <td colspan="2">Discoverer(s)</td> <td>Vogt et al.</td></tr><tr> <td colspan="2">Discovery method</td> <td>Doppler spectroscopy</td></tr><tr> <td colspan="2">Discovery site</td> <td>Template:Country data United States</td></tr><tr> <td colspan="2">Discovery status</td> <td>Confirmed</td></tr>

HD 217107 c is an extrasolar planet[1] approximately 64 light-years away from Earth in the constellation of Pisces (the Fish). The planet was the second planet to be discovered orbiting the star HD 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.

Detection and discovery Edit

A study of the radial 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 designated HD 217107 b, and was found to be somewhat heavier than Jupiter, and orbiting extremely close to the parent star in an orbit with quite a large eccentricity.[2]

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 several astronomical units (AU).[3] 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.[4]

See also Edit

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References Edit

External links Edit

Template:HD 217107 Coordinates: Sky map 22h 58m 15.54s, −02° 23′ 43.39″ Template:Star systems within 60 – 65 light-years Template:Stars of Pisces

Template:Good article

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