Thread: Iron Planet, any energy from gravity?

If you had an iron planet the size of Neptune for example, I presume the gravity would cause a lot of pressure in the core which would heat up the Iron and radiate into space.

a) Is this an inexhaustible source of energy?

b) where is the engery comming from, is the planet loosing mass?

No, to a and b. The heat energy of the core (caused by friction of the outer layers pushing inward) would eventually radiate outwards by convection and the planet would cool. The total energy would be zero, since it costs energy to create this iron giant in the first place.

So you would eventually have a core that is both densly packed by the massive gravity and nonetheless cold? I didnt know that, thanks.

Isn't it possible that the heawould be created by radioactive reaction as well?

Originally Posted by thyristor

Isn't it possible that the heawould be created by radioactive reaction as well?

Iron has the most stable nucleus of all the elements. Unless gravity crushed it to neutron star status there would, I suspect, be minimal conventional radioactivity.

A) - Not inexhaustible

B) - Of course it's losing mass, though maybe not very fast. (E = MC^2)


The previous posters are right that the heat would radiate out into space, but the planet would probably still be pretty hot most of the time because the vacuum of space is not the best heat conductor.

Neither fusion nor fission are likely to occur because Iron is at about the atomic weight that fission and fusion reactions get their energy by moving toward. It might still happen, but it would consume energy instead of creating it.

It is friction which creates heat energy, not the gravity. Generated heat will evaporate by conduction and radiation. Since the friction is generated by gravity which is a property of matter and no energy is used to maintain it, the radiated heat energy could also be free of cost!!!!!!!!!