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HD 217107 b

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

   CAPTION: HD 217107 b

     Extrasolar planet    Lists of extrasolar planets
                   Orbital elements
   Semimajor axis     (a) 0.074 ± 0.002 AU
   Eccentricity       (e) 0.13 ± 0.02
   Orbital period     (P) 7.1269 ± 0.00022 d
   Inclination        (i)  ?°
   Longitude of
   periastron         (ω) 21.1°
   Time of periastron (τ) 2,449,998.4241 ± 0.17 JD
               Physical characteristics
   Mass               (m) >1.37 ± 0.14 M[J]
   Radius             (r)  ? R[J]
   Density            (ρ)  ? kg/ m^3
   Temperature        (T)  ? K
                 Discovery information
   Discovery date         1998
   Discoverer(s)          Marcy et al.
   Detection method       Doppler Spectroscopy
   Discovery status       Confirmed

   HD 217107 b is an extrasolar planet orbiting the Sun-like star HD
   217107 every 7.1 days. It is the innermost known planet in its system,
   and was discovered by the California and Carnegie Planet Search team.
   It is a ' hot Jupiter' planet, so-called because of its high mass and
   proximity to its parent star.

Discovery

   As with the majority of extrasolar planet discoveries so far, it was
   found by detecting small variations in the radial velocity of the star
   it orbits, caused by the tug of its gravity. 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. The period and
   amplitude of this variation indicated that it was caused by a planetary
   companion in orbit around the star, with a minimum mass slightly
   greater than that of Jupiter . The planet's mean distance from the star
   is less than one fifth of Mercury's distance from the Sun.

Indication of second planet

   While most planets with orbital periods of less than 10 days have
   almost circular orbits, HD 217107 b has a somewhat eccentric orbit, and
   its discoverers hypothesised that this 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 a
   second planet, HD 217107 c, followed in 2005
   Retrieved from " http://en.wikipedia.org/wiki/HD_217107_b"
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   with only minor checks and changes (see www.wikipedia.org for details
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