The interior composition of exoplanets is not observable , limiting our direct knowledge of their structure , composition , and dynamics .
Recently described observational trends suggest that rocky exoplanets , that is , planets without significant volatile envelopes , are likely limited to < 1.5 Earth radii .
We show that given this likely upper limit in the radii of purely-rocky super-Earth exoplanets , the maximum expected core-mantle boundary pressure and adiabatic temperature is relatively moderate , 630 GPa and 5000 K , while the maximum central core pressure varies between 1.5 and 2.5 TPa .
We further find that for planets with radii less than 1.5 Earth radii , core-mantle boundary pressure and adiabatic temperature are mostly a function of planet radius and insensitive to planet structure .
The pressures and temperatures of rocky exoplanet interiors , then , are less than those explored in recent shock-compression experiments , ab-initio calculations , and planetary dynamical studies .
We further show that the extrapolation of relevant equations of state does not introduce significant uncertainties in the structural models of these planets .
Mass-radius models are more sensitive to bulk composition than any uncertainty in the equation of state , even when extrapolated to TPa pressures .