An Intensely Scorched Planet

Using data collected by NASA’s Kepler space telescope, a team of researchers have reported the discovery of an Earth-sized planet that whips around its parent star (KIC 8435766) in an 8.5-hour orbit. The planet was found as part of an effort to search for planets with very short orbital periods. This newfound planet is designated KIC 8435766b - basically adding a “b” to the back of the parent star’s designation. Some well-documented planets with orbits shorter than 1 day include Kepler-10b (20.1 hour orbit), Kepler-42c (10.9 hour orbit), COROT-7b (20.5 hour orbit) and 55 Cancri e (17.8 hour orbit). All these planets are smaller than twice the size of Earth.Figure 1: Artist’s impression of a rocky planet crossing in front of its parent star. Credit: Darke Max Macedo.Compared to small rocky planets, giant planets with orbits shorter than 1 day are less common and two such planets include WASP-43b (19.5 hour orbit) and WASP-19b (18.9 hour orbit). The rarity of giant planets with orbits shorter than 1 day suggests that giant planets are vulnerable to effects such as tidally-induced decay of their orbits and evaporation of their hydrogen-helium envelops. Since small rocky planets are less susceptible to these effects, they ...