HD 210277 and Its Solitary Known Planet

HD 210277 is a star 69.5 light-years away with one known planet in orbit around it. Its spectral type, G8/K0V, places it among the G- and K-type main-sequence dwarfs. The star is estimated to be 10.6 billion years old, with a mass of 0.99 solar masses, a radius of 1.06 solar radii, and a temperature of 5560 K. Its reported mass estimate is smaller than the Sun's, while its reported radius estimate is larger and its reported temperature is cooler.

The planet HD 210277 b was discovered in 1998 using the radial velocity method, which detects the wobble a planet's gravity induces in its star's motion, with repeated wobbles revealing the planet and its orbital period. The planet has a minimum mass of 410 Earth masses, a lower bound on its true mass rather than an ordinary estimate, and this minimum mass is larger than Earth's and roughly 1.29 times Jupiter's mass. It completes one orbit every 442 days.