HD 217107 b

HD 217107 b

Discovery
Discovered by	Marcy et al.
Discovery site	United States
Discovery date	November 24, 1998
Detection method	Doppler spectroscopy
Orbital characteristics
Semi-major axis	0.07505±0.00097 AU
Eccentricity	0.1283±0.0027[1]
Orbital period (sidereal)	7.126846±0.000013[1] d
Time of periastron	2454395.789±0.025[1]
Argument of periastron	24.0±1.3[1]
Semi-amplitude	140.30±0.40[1]
Star	HD 217107

HD 217107 b is an extrasolar planet^[2] approximately 65 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).

Discovery

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.^[3] 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).^[4] Confirmation of the existence of a second planet, HD 217107 c, followed in 2005.

See also

• HD 217107
• HD 217107 c
• List of exoplanets discovered before 2000

References

1. Feng, Y. Katherina; et al. (2015). "The California Planet Survey IV: A Planet Orbiting the Giant Star HD 145934 and Updates to Seven Systems with Long-period Planets". The Astrophysical Journal. 800 (1). 22. arXiv:1501.00633. Bibcode:2015ApJ...800...22F. doi:10.1088/0004-637X/800/1/22. S2CID 56390823.
2. Vogt, Steven S.; et al. (2005). "Five New Multicomponent Planetary Systems" (PDF). The Astrophysical Journal. 632 (1): 638–658. Bibcode:2005ApJ...632..638V. doi:10.1086/432901. S2CID 16509245.
3. Fischer, Debra A.; 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. S2CID 17980987.
4. Fischer, Debra A.; 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.

External links

• "HD 217107 / HR 8734". SolStation. Retrieved 2008-06-23.
• "Notes for planet HD 217107 b". Extrasolar Planets Encyclopaedia. Retrieved 2008-06-23.