The KELT-21 Exoplanetary System
KELT-21 is a star with 1.46 times the mass of the Sun, and 1.64 times its radius. It is located 1353.55 light years away from the solar system and is estimated to be 1.6 billion years old, as compared to the Sun which is roughly 4.6 billion years old.
KELT-21 is known to have 1 exoplanets in orbit around it.
KELT-21 b was discovered by the KELT-North observatory using the transit method. Its semi-major axis is 0.05 astronomical units, as compared to Earth's which is 1 astronomical unit. It takes 3.61 Earth days to complete an orbit around its host star, KELT-21.
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 KELT-21 b is at is at its closest point to its host star, 0.05 astronomical units separates the two, and when it is at its farthest point, this number is 0.05. In the case of Earth, these numbers are 0.9832899 and 1.0167103 respectively.
The mass of KELT-21 b is 1242.64 times the mass of Earth. The radius of KELT-21 b is 17.777 that of Earth. At more than 50 Earth masses, KELT-21 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.