__NOTOC__ HD 156668 b is an

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

orbiting the star HD 156668 78.5 light-years away in the constellation

Hercules Hercules (, ) is the Roman equivalent of the Greek divine hero Heracles, son of Jupiter and the mortal Alcmena. In classical mythology, Hercules is famous for his strength and for his numerous far-ranging adventures. The Romans adapted the ...

. 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 Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in t ...

after Gliese 581 e, subject to the mass/inclination degeneracy that affects radial velocity measurements. 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. This planet was discovered on January 6, 2010; it is the 8th planet discovered in 2010 after the first five planets detected by

Kepler Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and writer on music. He is a key figure in the 17th-century Scientific Revolution, best known for his laws o ...

on January 4 and two planets around HD 9446 on January 5.

References

Exoplanets discovered in 2010 Exoplanets detected by radial velocity Super-Earths Hercules (constellation) {{extrasolar-planet-stub