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HD 217107 c

2007 Schools Wikipedia Selection. Related subjects: Space (Astronomy)

   CAPTION: HD 217107 c

     Extrasolar planet    Lists of extrasolar planets
                   Orbital elements
   Semimajor axis     (a) 4.3 ± 2 AU
   Eccentricity       (e) 0.55 ± 0.20
   Orbital period     (P) 3150 ± 1000 d (8.6 y)
   Inclination        (i) °
   Longitude of
   periastron         (ω) 164 ± 30.2°
   Time of periastron (τ) 2,451,030 ± 300 JD
               Physical characteristics
   Mass               (m) >2.1 ± 1 M[J]
   Radius             (r)  ? R[J]
   Density            (ρ)  ? kg/ m^3
   Temperature        (T)  ? K
                 Discovery information
   Discovery date         1999-2005
   Discoverer(s)          Marcy et al.
   Detection method       Doppler Spectroscopy
   Discovery status       Confirmed

   HD 217107 c is a Jupiter-like extrasolar planet orbiting the star HD
   217107 about every eight years. It is the second planet to be
   discovered orbiting the star, after HD 217107 b which orbits the star
   in a much smaller orbit. HD 217107 c's existence was hypothesised in
   2002 and confirmed in 2005, when radial velocity studies of the star
   indicated another, more distant and massive companion orbiting the
   star. Its mass and orbital parameters remain highly uncertain.

Discovery

   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 .

   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). Confirmation of the existence of the second
   planet followed in 2005, and it was designated HD 217107 c.

Orbit

   Observations of the star's radial velocity variations indicate a period
   of about 8 years, and HD 217107 c's mass is thought to be at least
   twice that of Jupiter in a very eccentric orbit with a semimajor axis
   of about 4 AU . Large uncertainties still exist in these measurements,
   though, due to the length of the orbital period and the distance of HD
   217107 c from its parent star.

   Retrieved from " http://en.wikipedia.org/wiki/HD_217107_c"
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   with only minor checks and changes (see www.wikipedia.org for details
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