A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at 30 pc

Abstract

We report the discovery of three small transiting planets orbiting GJ 9827, a bright (K = 7.2) nearby late K-type dwarf star. GJ 9827 hosts a 1.62 ± 0.11 R⊕ super Earth on a 1.2 day period, 1.269[subscript -00.089][superscript +0.087] R⊕ a super Earth on a 3.6 day period, and a 2.07 ± 0.14 R⊕ super Earth on a 6.2 day period. The radii of the planets transiting GJ 9827 span the transition between predominantly rocky and gaseous planets, and GJ 9827 b and c fall in or close to the known gap in the radius distribution of small planets between these populations. At a distance of 30 pc, GJ 9827 is the closest exoplanet host discovered by K2 to date, making these planets well-suited for atmospheric studies with the upcoming James Webb Space Telescope. The GJ 9827 system provides a valuable opportunity to characterize interior structure and atmospheric properties of coeval planets spanning the rocky to gaseous transition.