Abstract

Poster - Splinter Exoplanets

Friday, 17 September 2021, 16:22   (virtual Exo)

Effects of tidal heating in Proxima Centauri b's thermal evolution

Enrique Sanchis, Lena Noack
Freie Universitaet Berlin

The recent discovery of a terrestrial planet orbiting Proxima Centauri, our closest neighbor (an M5.5V star of 0.1 MSun mass and only 1.3 pc distance to the Sun), offers an excellent planet laboratory to study the most important theories of planet evolution and composition. The planet (Proxima b) is orbiting the star in its habitable zone at a separation of only ~0.05 AU and an orbital period of ~11 days, and most recent studies suggest a non-zero eccentricity of about 0.17. With a mass of >=1.2 MEarth, Proxima b is expected to have a rocky composition, which might resemble the Earth. It is therefore an excellent target to characterize terrestrial planets similar to Earth, avoiding the inherent biases of only studying the terrestrial planets of the solar system. Due to its close orbit and expected eccentricity, Proxima b most likely suffers from severe tidal heating, which can have an extreme incidence in the planet's habitability and the survival of an atmosphere. In this work, we perform a comprehensive analysis of the incidence that different distribution patterns of tidal heating can have on Proxima b's interior and thermal evolution. To accomplish this goal, we consider various cases for the tidal heat distribution, which depend on the assumed planet's interior structure. In the simplest case, the distribution is homogeneous throughout the interior of the planet. More complicated distribution patterns with radial and/or lateral dependence (for a homogeneous body, for a two-shell body with a differentiated core; Beuthe 2013) are also investigated. The different models alter how tidal heat is distributed throughout the planet's interior, which can highly affect its overall thermal evolution. Furthermore, due to its proximity to the central star, Proxima b may as well be in synchronous rotation with Proxima Centauri. This can cause an extreme surface temperature variation between the hemisphere that permanently faces the star and the opposite hemisphere. In this work, the effect that synchronous rotation may have on Proxima b's interior is also explored.