HD 156668 b

HD 156668 b is an extrasolar planet orbiting the star HD 156668 78.5 light-years away in the constellation Hercules. It has a minimum mass of 3.1 Earth masses. At the time of discovery it was the second least massive planet discovered by the radial velocity method, subject to the mass/inclination degeneracy that affects radial velocity measurements.[3] The only radial velocity planet less massive than this planet is Gliese 581 e, which was discovered on April 21, 2009, and has a minimum mass of 1.94 Earth masses. In addition to this, it has the lowest semi-amplitude, or the speed of the stellar wobble caused by planet's gravity tugging on the star determined by radial velocity, at 2.2 m/s.[3] This planet was discovered on January 6, 2010; it is the 8th planet discovered in 2010 after the first five planets detected by Kepler on January 4 and two planets around HD 9446 on January 5.

HD 156668 b
Discovery
Discovered byHoward et al.
Discovery siteKeck Observatory
Discovery date2010-01-06
Doppler Spectroscopy
Orbital characteristics
0.04998 ± 0.00083 AU (7,477,000 ± 124,000 km)[1]
Eccentricity0.000[2]
4.6455 ± 0.0011[1] d
0[2]
Semi-amplitude1.89 ± 0.26 [1]
StarHD 156668

    References
    1. Andrew W. Howard; John Asher Johnson; Geoffrey W. Marcy; Debra A. Fischer; Jason T. Wright; Gregory W. Henry; Howard Isaacson; Jeff A. Valenti; Jay Anderson; Nikolai E. Piskunov (2010). "The NASA-UC Eta-Earth Program: II. A Planet Orbiting HD 156668 with a Minimum Mass of Four Earth Masses". The Astrophysical Journal. 726 (2): 73. arXiv:1003.3444v1. Bibcode:2011ApJ...726...73H. doi:10.1088/0004-637X/726/2/73. S2CID 15559379.
    2. Dawson, Rebekah I.; Fabrycky, Daniel C. (2010). "Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e". The Astrophysical Journal. 722 (1): 937–953. arXiv:1005.4050. Bibcode:2010ApJ...722..937D. doi:10.1088/0004-637X/722/1/937. S2CID 118592734.
    3. "Second Smallest Exoplanet Found To Date At Keck". W.M. Keck Observatory. 2010-01-07. Retrieved 2010-01-07.


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