HD 217107 b
|Extrasolar planet||List of extrasolar planets|
|Right ascension||(α)||22h 58m 15.54s|
|Declination||(δ)||−2° 23′ 43.39″|
|Distance||64.3 ± 1 ly
(19.7 ± 0.3 pc)
|Semimajor axis||(a)||0.074 ± 0.002 AU|
|Eccentricity||(e)||0.13 ± 0.02|
|Orbital period||(P)||7.1269 ± 0.00022 d|
|Time of periastron||(T0)||2,449,998.4241 ± 0.17 JD|
|Semi-amplitude||(K)||140.7 ± 2.6 m/s|
|Mass||(m)||>1.37 ± 0.14 MJ|
|Discovery date||November 24, 1998|
|Discoverer(s)||Marcy et al.|
|Discovery method||Doppler spectroscopy|
|Discovery site||United States|
HD 217107 b is an extrasolar planet approximately 64 light-years away from Earth in the constellation of Pisces (the Fish). The planet was discovered orbiting the star HD 217107 approximately every seven days, classifying the planet as a hot Jupiter. Because of the planet's somewhat eccentric orbit, scientists were able to confirm another planet within the system (HD 217107 c).
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 hypothesized 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.
- Vogt, Steven S. et al. (2005). "Five New Multicomponent Planetary Systems". The Astrophysical Journal 632 (1): 638–658. Bibcode:2005ApJ...632..638V. doi:10.1086/432901.
- Fischer et al. (1999). "Planetary Companions around Two Solar-Type Stars: HD 195019 and HD 217107". Publications of the Astronomical Society of the Pacific 111 (755): 50–56. arXiv:astro-ph/9810420. Bibcode:1999PASP..111...50F. doi:10.1086/316304.
- Fischer et al. (2002). "Planetary Companions to HD 12661, HD 92788, and HD 38529 and Variations in Keplerian Residuals of Extrasolar Planets". The Astrophysical Journal 551 (2): 1107–1118. Bibcode:2001ApJ...551.1107F. doi:10.1086/320224.
- "HD 217107 / HR 8734". SolStation. Retrieved 2008-06-23.
- "Notes for planet HD 217107 b". The Extrasolar Planets Encyclopaedia. Retrieved 2008-06-23.