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

[Flyndaran]

Originally Posted by Anthony

Brown dwarfs are stars, not planets.

They are in between stars and planets.

[scc]

Originally Posted by Flyndaran

They are in between stars and planets.

Yep, and my point was that some specific sort of fusion, I can't recall off the top of my head, has to occur before a planet is classified as a Brown Dwarf, without that happening its still a planet

[Anthony]

Originally Posted by scc

Yep, and my point was that some specific sort of fusion, I can't recall off the top of my head

Deuterium fusion. The line between red dwarf and brown dwarf is hydrogen (protium) fusion.

[Flyndaran]

Originally Posted by Anthony

Deuterium fusion. The line between red dwarf and brown dwarf is hydrogen (protium) fusion.

And isn't modern astronomy always finding objects right in what we thought were nicely defined no man's lands between categories?

[Anthony]

Originally Posted by Flyndaran

And isn't modern astronomy always finding objects right in what we thought were nicely defined no man's lands between categories?

It's not a "no man's land" in this case. It's not entirely certain what the critical mass is, but it can either fuse hydrogen or it can't.

[Fred Brackin]

Originally Posted by Anthony

Deuterium fusion. The line between red dwarf and brown dwarf is hydrogen (protium) fusion.

.....and there are no celestial bodies (star or planet) that are too small to fuse deuterium but can still fuse some other type of hydrogen.

[Anthony]

Originally Posted by Fred Brackin

.....and there are no celestial bodies (star or planet) that are too small to fuse deuterium but can still fuse some other type of hydrogen.

Well, in principle you might have something only big enough to fuse tritium, but with a half-life of 12 years you can't possibly have enough tritium to matter.

[Kraydak]

Originally Posted by Anthony

Brown dwarfs are stars, not planets.

For reference, there are two competing dividing lines between brown dwarfs and (really, REALLY) big gas giant planets.

1) Deuterium burning. This has some observational consequences for some objects, but is otherwise really, really boring. It just measures mass.

2) Formation mechanism (direct gravitational collapse, like a star, or core-accretion building up a rocky core, like a planet). While more conceptually useful than definition (1), it doesn't make any observational predictions…

[Anthony]

Originally Posted by Kraydak

2) Formation mechanism (direct gravitational collapse, like a star, or core-accretion building up a rocky core, like a planet). While more conceptually useful than definition (1), it doesn't make any observational predictions…

And it is not entirely obvious that there is any firm distinction between those two methods, or that you can't have two apparently identical objects that formed by different means.

[Captain Joy]

Originally Posted by Kraydak

2) Formation mechanism (direct gravitational collapse, like a star, or core-accretion building up a rocky core, like a planet). While more conceptually useful than definition (1), it doesn't make any observational predictions…

Direct gravitational collapse alone would result in an object with a solar nebula abundance. Core-accretion would result in an object with greater amounts of metals, rocky material, and possibly ices. It is possible that such a difference could be measurable or at least rule out certain formation models for certain objects.

To bring this back on topic: it seems based on everything I'm hearing that you can safely ignore the heat given off by a gas giant for it's moons, unless your system is still in the process of forming.