TESS Discovery of an Ultra-short-period Planet around the Nearby M Dwarf LHS 3844

Abstract

Data from the newly commissioned Transiting Exoplanet Survey Satellite has revealed a "hot Earth" around LHS 3844, an M dwarf located 15 pc away. The planet has a radius of $1.303\pm 0.022$ R ⊕ and orbits the star every 11 hr. Although the existence of an atmosphere around such a strongly irradiated planet is questionable, the star is bright enough (I = 11.9, K = 9.1) for this possibility to be investigated with transit and occultation spectroscopy. The star's brightness and the planet's short period will also facilitate the measurement of the planet's mass through Doppler spectroscopy.