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Moon orbiting close to its host planet

by willstaruss22
Tags: host, moon, orbiting, planet
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willstaruss22
#1
Aug18-13, 12:58 AM
P: 96
Can a moon orbit close to its host planet and have no tidal heating?
Say there is a moon with 0.5 Earth masses and 0.8 Earth radii orbiting a Jupiter mass planet every 18 hours with an eccentricity of 0.00001. There are no moons within 3 million miles of the exomoon in question. Could this moon have limited to no tidal heating or does the proximity of the moon to the host planet guarantee some tidal heating?
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tiny-tim
#2
Aug18-13, 04:46 AM
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hi willstaruss22!

tidal heating is caused by squeezing and stretching as the moon changes shape

the change of shape is caused by the gravitational force changing on
different parts of the moon

if the moon has a perfectly circular orbit (and the planet has a perfectly circular gravitational field), and if the moon always keeps the same face towards the planet, then there wil be no change in the gravitational field, and no tidal forces or tidal heating
in any other case, there will be
snorkack
#3
Aug18-13, 05:08 AM
P: 381
Proximity of the planet is not very relevant. There IS a minimum level of tidal acceleration gradient due to the star. Meaning that the moon will experience solar tides, just like a lone planet would.

There is a small relevance to the proximity of the planet: the distance to the planet dictates the period of solar tides, and therefore their heat production.

The planetary tides can be arbitrarily weak, because the orbit can be arbitrarily close to circle. They, however, can only amplify tides: they cannot in long term cancel the solar tides because they have different period. Solar tides have about two high tides per orbit, tides due to eccentric orbit have one high tide per orbit.


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