KOI-2138.01: a 2.1 Earth Radius SuperEarth in a 23.55 Day Orbit

Probable Spin-Orbit Aligned Super-Earth Planet Candidate KOI-2138.01

Authors:

Barnes et al

Abstract:

We use rotational gravity darkening in the disk of Kepler star KOI-2138 to show that the orbit of 2.1−R⊕ transiting planet candidate KOI-2138.01 has a low projected spin-orbit alignment of λ=1∘±13. KOI-2138.01 is just the second super-Earth with a measured spin-orbit alignment after 55 Cancri e, and the first to be aligned. With a 23.55-day orbital period, KOI-2138.01 may represent the tip of a future iceberg of solar-system-like terrestrial planets having intermediate periods and low-inclination circular orbits.