Approximate Calculation of the Thermal Loss of the Atmosphere of a Hot Exoplanet in a Low Orbit with Taking into Account the Ellipticity

The paper presents the results of calculations using an approximate approach to estimating the thermal loss of the atmosphere of a hot exoplanet. The objective of simulation was to study a system of a yellow dwarf of the spectral type G with an exoplanet like a hot sub-Neptune or super-Earth. Estimates of the atmospheric loss rate for a hot sub-Neptune in weakly and strongly elliptical orbits are obtained. Calculations have shown that the atmospheric loss Ṁ_T averaged over the orbital period of the model hot sub-Neptune varies from 5.8× 10^17 g for an orbit with e=0.0 to 2.6× 10^18 g for an orbit with e=0.8 , that is, it increases by almost 4.5 times. Moreover, for e=0.2,0.4, and 0.6 the values of Ṁ_T are equal to 6.3× 10^17 g, 7.6× 10^17 g, and 1.2× 10^18 g respectively. Using the average atmospheric mass loss per orbit, we can approximately estimate the time of total atmospheric escape of the considered sub-Neptune—at e=0.0 , this time is approximately equal to 0.32 billion years, and at e=0.8 —approximately 0.07 billion years. Accordingly, we can conclude that the initial ellipticity of the hot exoplanet’s orbit is an important factor in estimating the loss rate of the primary hydrogen-helium atmosphere for sub-Neptunes and super-Earths.