[Space] How much does a Gas Giant heat it's moons?

[Nereidalbel]

For one, Jupiter's albedo is .343, not .5. Also, Space uses AU for measuring distances within solar systems, not kilometers. Try the math again and see what happens!

[malloyd]

Originally Posted by David Johnston2

Don't bother. It would be a fraction of a degree.

Mostly. In the limiting case after you could imagine the moon always sat exactly between the sun and the gas giant, and the gas giant was a perfect mirror and so much bigger than the moon you could treat it as a flat one. This completely ridiculous arrangement maximizes the amount of light falling on the moon. It doubles it, which raises its temperature by the fourth root of 2 (i.e. about 19%).

The heating gas giants do of their moons isn't radiant, it's tidal. Maybe occasionally there'll be some meaningful magnetic effects too, at least on the air temperature of something with an atmosphere, but reflected light isn't going to contribute very much.