Fictitious Planet Details.
For a personal project of mine, I am creating a fictitious solar system with planets that can sustain life. To make the project more realistic, I have a set of rules. Mainly, the planet and its inhabitants have to able to exist. I really want a unique planet, and I have it all figured out, except for one thing. The core. So, my question is this:
Could a planet have a gaseous core, and have it very dense and hot, much like a little star, as well as a solid outside?
If so, how could it have formed?