What would happen when a planet consumed all its fuel and its core extincts. Would anything change on the planet?
Can this ever happen before its star did so? If not, why?
What would happen when a planet consumed all its fuel and its core extincts. Would anything change on the planet?
Can this ever happen before its star did so? If not, why?
The core of the Earth is hot because of its own density and radioactive materials. Basically, the more you compress an object, the hotter it gets. It does not undergo fusion, since only massive (stellar) objects do so. A significant amount of radioactive decay happens in the core, which is mainly the source of its heat, but no fusion.
Similarly, stars are hot because of their own densities, but at a much larger scale, and sans the nuclear decay. This is especially evident when stars are born as non-fusing protostars; they are prevented from getting smaller because as they do so, their core will get hotter. Hotter objects actually expand, so protostars are in a state of equilibrium; if they get any smaller, the temperatures will increase and they will become larger again.
However, protostars slowly get smaller and smaller over time. This is because they lose energy as they emit light. Light emission is, in fact, a source of energy loss. So the star will continue to collapse slowly, and once the core reaches a certain density, it will begin fusing hydrogen. This produces radiation pressure, which counters the force of gravity.
Again, let me clear up something: nucleosynthesis in stars does not cause heat, but rather it prevents the star's gravitational collapse. It's the star's density that causes such high temperatures. If a star runs out of "fuel", that spells out the last phases of its life — as far as I know, the end result reaches extremely high temperatures (supernovae, white dwarfs, etc.)
A planet does not have any fuel. Only stars "burn" fuel either in their cores or concentric shells around their cores.