The HD 81817 Exoplanetary System
HD 81817 is a star with 4.3 times the mass of the Sun, and 83.8 times its radius. It is located 877.26 light years away from the solar system and is estimated to be 0.15 billion years old, as compared to the Sun which is roughly 4.6 billion years old.
HD 81817 is known to have 1 exoplanets in orbit around it.
HD 81817 b
HD 81817 b was discovered by the Bohyunsan Optical Astronomical Observatory observatory using the radial velocity method. Its discovery was announced in 2020-05. Its semi-major axis is 3.30 astronomical units, as compared to Earth's which is 1 astronomical unit. It takes 1047.10 Earth days to complete an orbit around its host star, HD 81817.
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 0.17, which means that when HD 81817 b is at is at its closest point to its host star, 2.74 astronomical units separates the two, and when it is at its farthest point, this number is 3.86. In the case of Earth, these numbers are 0.9832899 and 1.0167103 respectively.
The mass of HD 81817 b is 8612.67 times the mass of Earth. At more than 50 Earth masses, HD 81817 b is a gas giant, a planet whose mass is mostly made up of hydrogen and helium, like Jupiter and Saturn in our solar system.