The Pressure and Temperature Limits of Likely Rocky Exoplanets. (arXiv:1905.06530v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Unterborn_C/0/1/0/all/0/1">Cayman T. Unterborn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Panero_W/0/1/0/all/0/1">Wendy R. Panero</a>
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.
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.
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