NN Ser: A White Dwarf Host with Two Circumbinary Planets

NN Ser is a binary star system 1680 light-years away. The host star is a white dwarf with a mass of 0.535 solar masses, smaller than the Sun's, and a temperature of 57000 K, hotter than the Sun's. Two planets orbit this host: NN Ser c and NN Ser d. Both are circumbinary, meaning they orbit both stars of the binary system rather than one star alone.

Both planets were discovered in 2010 through Eclipse Timing Variations. NN Ser c has a minimum mass of 3090 Earth masses, a lower bound on its true mass, and roughly 9.71 times Jupiter's mass; its minimum mass is larger than Earth's. Its orbital period is 6990 days, the longest year among the listed planets. NN Ser d has a minimum mass of 696 Earth masses, also a lower bound, and roughly 2.19 times Jupiter's mass; its minimum mass is larger than Earth's. Its orbital period is 2880 days, the shortest year among the listed planets. NN Ser d has the smallest minimum mass of the pair, while NN Ser c has the largest.