Why hot Jupiters can be large but not too large. (arXiv:2201.07008v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hou_Q/0/1/0/all/0/1">Qiang Hou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wei_X/0/1/0/all/0/1">Xing Wei</a>
Tidal heating is often used to interpret “radius anomaly” of hot Jupiters
(i.e. radii of a large fraction of hot Jupiters are in excess of 1.2 Jupiter
radius which cannot be interpreted by the standard theory of planetary
evolution). In this paper we find that tidal heating induces another phenomenon
“runaway inflation” (i.e. planet inflation becomes unstable and out of control
when tidal heating rate is above its critical value). With sufficiently strong
tidal heating, luminosity initially increases with inflation, but across its
peak it decreases with inflation such that heating is stronger than cooling and
runaway inflation occurs. In this mechanism, the opacity near
radiative-convective boundary (RCB) scales approximately as temperature to the
fourth power and heat cannot efficiently radiate away from planet interior,
which induces runaway inflation (similar to a tight lid on a boiling pot).
Based on this mechanism, we find that radii of hot Jupiters cannot exceed
$2.2R_J$, which is in good agreement with the observations. We also give an
upper limit for orbital eccentricity of hot Jupiters. Moreover, by comparison
to the observations we infer that tidal heating locates near RCB.
Tidal heating is often used to interpret “radius anomaly” of hot Jupiters
(i.e. radii of a large fraction of hot Jupiters are in excess of 1.2 Jupiter
radius which cannot be interpreted by the standard theory of planetary
evolution). In this paper we find that tidal heating induces another phenomenon
“runaway inflation” (i.e. planet inflation becomes unstable and out of control
when tidal heating rate is above its critical value). With sufficiently strong
tidal heating, luminosity initially increases with inflation, but across its
peak it decreases with inflation such that heating is stronger than cooling and
runaway inflation occurs. In this mechanism, the opacity near
radiative-convective boundary (RCB) scales approximately as temperature to the
fourth power and heat cannot efficiently radiate away from planet interior,
which induces runaway inflation (similar to a tight lid on a boiling pot).
Based on this mechanism, we find that radii of hot Jupiters cannot exceed
$2.2R_J$, which is in good agreement with the observations. We also give an
upper limit for orbital eccentricity of hot Jupiters. Moreover, by comparison
to the observations we infer that tidal heating locates near RCB.
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