BD+20 2457: A Distant Star With Two Massive Planets

BD+20 2457 is a star located 5020 light-years away. Its spectral type, K2 II, indicates a cool, bright star, and its measured properties are extreme: a mass of 2.8 solar masses, a radius of 49 solar radii, and a temperature of 4140 K. The star is larger than the Sun in both mass and radius, but cooler than the Sun. Two planets orbit this host.

Both planets were discovered in 2009 using the radial velocity method, which measures the wobble a planet's gravity induces in its star's motion. BD+20 2457 b has a minimum mass of 6810 Earth masses, meaning its true mass is at least that value, and an orbital period of 380 days. This makes it the shortest-period planet among the listed worlds and the most massive by minimum mass, with a minimum mass roughly 21.4 times Jupiter's mass. BD+20 2457 c has a minimum mass of 3960 Earth masses and an orbital period of 622 days, giving it the longest period among the listed planets and the smallest minimum mass. Its minimum mass is roughly 12.5 times Jupiter's mass. Both planets' minimum masses are larger than Earth's.