Quote:
Originally Posted by m1omg
http://en.wikipedia.org/wiki/Gliese_...Orbit_and_mass
"Due to its extremely eccentric orbit, models predict that tidal heating will play a significant role in the planet's geology. In fact, they predict that the planet may well be kept in a completely molten state. Predicted total heat flux is approximately 10(exponent)4-5 W/m2 at the planet's surface; for comparison the surface heat flux for Io is around 3 W/m2.[4]
[edit] "
???Which one is right?
References http://arxiv.org/abs/0803.0026 .
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Hmm... Notice: "heat flux
at the planet's surface". That's because surface (well, top kilometer or so) is where tidal heat is generated. Eventually it is distributed through the planet's mass. That's why I wrote "much greater total mass of the tidal buldge is balanced out by proportionally greater mass of the planet to absorb the heat". Total amount of heat energy generated is proporional to the planet's mass, so if Gliese 876 d is 7.5 mass of Earth = 500 times mass of Io, then total heat flux (for my upper value) is 46*500 = 23,000 times. With Gliese 876 d's diameter likely 6-7 times that of Io (if its density equals to or more than Earth), surface area is 35-50 Io's. I get heat flux per square meter between 23,000/35 and 23,000/50 -- 460 to 660 times. Do not see how you could possibly get 10
4-5.
But that does not make actual
heat energy is 460-660 times that on Io. Because eventually it does distribute through planet's mass. OTOH, 46 times heat energy is more than enough to keep the surface molten.