HD 89345 b

HD 89345 b is a Neptune-like exoplanet that orbits a G-type star. It is also called K2-234b. Its mass is equivalent to 35.7 Earths, it takes 11.8 days to complete one orbit of its star, and is 0.105 AU away from its star. It was discovered by a team of 43 astrophysicists, one of which was V. Van Eylen, and was announced in 2018.

Overview
The exoplanet HD 89345 b, which has a mass of 0.1 and a radius of 0.61, was assigned to the class of ocean planets. The parent star of the planet, which is about 5.3 billion years old, belongs to the spectral class of G5V-G6V. It is 66 percent larger and 22 percent more massive than the Sun, and is located 413 light-years away. The effective temperature of the star is 5609 K. Considering that HD 89345 b makes one revolution around the star in 11.8 days at a distance of 0.11 AU, this planet was described by researchers as a warm subterranean with an equilibrium temperature of 1059 K.

Discovery
HD 89345 b, a Saturn-sized exoplanet orbiting a slightly evolved star HD 89345, was discovered in 2018 using the transit photometry method, the process that detects distant planets by measuring the minute dimming of a star as an orbiting planet passes between it and the Earth. It is the only planet orbiting around HD 89345, a G5 class star, situated in the constellation of Leo in 413 light-years from the Sun. This star is aged 9.4 billion years. HD 89345 b orbits its star in about 12 terrestrial days in an elliptical orbit. The orbit is closer to the star than the inner limit of the habitable zone. It has a low density and can be composed of gas.

Its parent star, HD 89345, is a bright star (apparent magnitude 9.3) observed by the K2 mission with one-minute time sampling. It exhibits solar-like oscillations. The data is collected by asteroseismology, which enables to determine the parameters of the star and find its mass and radius. Its mass is 1.12$$ and its mean radius is 1.657$$. The star appears to have recently left the main sequence, based on the inferred age, 9.4$$ Gyr, and the non-detection of mixed modes. The star hosts a "warm Saturn" with an orbital period of approximately 11.8 days and a radius of $6.86 Earth radius$. Radial-velocity follow-up observations performed with the FIES, HARPS, and HARPS-N spectrographs show that the planet has a mass of $35.7 Earth mass$. The data also show that the planet's orbit is eccentric ($$e \thickapprox 0.2 $$).