Size/Mass of a planet needed in order to have a molten core or a magnetic field?

jarroe

How big does a planet have to be in order for it to have a molten core or a magnetic field? Assuming no other large objects were close enough to affect the planet with their own pull or magnetic field. I would imagine the composition/density of the planet would play a factor as well, but do we have any formulas out there that would descibe this. Perhaps we don't have enough samples/data to make an informed decision on this yet?

jarroe

Age of the planet would factor in as well Im sure?

jedishrfu

I'm not sure there such a limit but rather how it was formed and what it's made of

See Wikipedia article:

http://en.wikipedia.org/wiki/Planetary_core

SpiffyKavu

Also take notice of Neptune and Uranus.

http://en.wikipedia.org/wiki/Uranus#Magnetic_field

It is thought that the magnetic field is generated in a liquid layer; not the core.