HD 191939 is a star with 0.92 times the mass of the Sun, and 0.94 times its radius. It is located 174.85 light years away from the solar system and is estimated to be 7 billion years old, as compared to the Sun which is roughly 4.6 billion years old.
HD 191939 is known to have 3 exoplanets in orbit around it.
HD 191939 b was discovered by the Transiting Exoplanet Survey Satellite (TESS) observatory, in 2020-02, using the transit method. Its semi-major axis is 0.08 astronomical units, as compared to Earth's which is 1 astronomical unit. The mass of HD 191939 b is 11.575 times the mass of Earth. The radius of HD 191939 b is 3.420 that of Earth. At more than 10 Earth masses, HD 191939 b 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.
HD 191939 c was discovered by the Transiting Exoplanet Survey Satellite (TESS) observatory, in 2020-02, using the transit method. Its semi-major axis is 0.18 astronomical units, as compared to Earth's which is 1 astronomical unit. The mass of HD 191939 c is 10.526 times the mass of Earth. The radius of HD 191939 c is 3.230 that of Earth. At more than 10 Earth masses, HD 191939 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.
HD 191939 d was discovered by the Transiting Exoplanet Survey Satellite (TESS) observatory, in 2020-02, using the transit method. Its semi-major axis is 0.21 astronomical units, as compared to Earth's which is 1 astronomical unit. The mass of HD 191939 d is 10.144 times the mass of Earth. The radius of HD 191939 d is 3.160 that of Earth. At more than 10 Earth masses, HD 191939 d 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.