Observability of the 10 μm emission excess due to tidal heating in a period-eccentricity diagram. a) Dashed contours indicate the circularization timescale (e / ė), solid contours give the planet/star contrast ratio in ppm, and the dotted contours show the ratio between the emission due to tidal heating and the emission without tidal heating. The contours are calculated for a 0.2  M_⊙ star, A = 0.2, an isothermal surface (stellar and internal flux fully redistributed), a 2  R_⊕ planet and the dissipation parameters of the Earth. The colored area represents the observability domain for the tidal heating, where the configuration lasts for more than 1 Gyr, produce a planet/star contrast higher than 10 ppm and results in tidal heating contributing to more than 10% of the emission. Panels b), c) and d) respectively show the influence of the stellar mass, the planetary radius and the dissipation factor on this tidal heating observability domain.