The HD 219666 Exoplanetary System
HD 219666 is a star with 0.92 times the mass of the Sun, and 1.03 times its radius. It is located 307.99 light years away from the solar system and is estimated to be 10 billion years old, as compared to the Sun which is roughly 4.6 billion years old.
HD 219666 is known to have 1 exoplanets in orbit around it.
HD 219666 b
HD 219666 b was discovered by the Transiting Exoplanet Survey Satellite (TESS) observatory using the transit method. Its semi-major axis is 0.06 astronomical units, as compared to Earth's which is 1 astronomical unit. It takes 6.04 Earth days to complete an orbit around its host star, HD 219666.
Its eccentricity, the extent to which the shape of the exoplanet's orbit departs from a perfect circle (Earth's is 0.0167, which is why the shape of Earth's orbit is circular rather than oval in appearance), is 0, which means that when HD 219666 b is at is at its closest point to its host star, 0.06 astronomical units separates the two, and when it is at its farthest point, this number is 0.06. In the case of Earth, these numbers are 0.9832899 and 1.0167103 respectively.
The mass of HD 219666 b is 16.60 times the mass of Earth. The radius of HD 219666 b is 4.71 that of Earth. At more than 10 Earth masses, HD 219666 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.