HD 156668 is a star with 0.77 times the mass of the Sun, and 0.72 times its radius. It is located 79.36 light years away from the solar system and is estimated to be 8.6 billion years old, as compared to the Sun which is roughly 4.6 billion years old.
HD 156668 is known to have 2 exoplanets in orbit around it.
HD 156668 b was discovered by the W. M. Keck Observatory observatory, in 2011-01, using the radial velocity method. Its semi-major axis is 0.05 astronomical units, as compared to Earth's which is 1 astronomical unit. The mass of HD 156668 b is 4.134 times the mass of Earth. The radius of HD 156668 b is 1.870 that of Earth. With a mass below 5 Earth masses, a density of 3.49, and a semi-major axis of 0.05 astronomical units, HD 156668 b could, potentially, be an ocean world - a planet with no dry land.
HD 156668 c was discovered by the Multiple Observatories observatory, in 2021-05, using the radial velocity method. Its semi-major axis is 1.57 astronomical units, as compared to Earth's which is 1 astronomical unit. The mass of HD 156668 c is 31.514 times the mass of Earth. The radius of HD 156668 c is 6.170 that of Earth. At more than 10 Earth masses, HD 156668 c is an ice giant, a planet that is made up mostly of volatiles like water, amonia and methane, and enveloped by a dense hydrogen and helium atmosphere, much like Uranus and Neptune in our solar system.