Maybe a hollow planet or a hollow and big asteroid could exist,
According to this theory, not all planets are hollow.
Mars would also have an internal start based on this, which tracks, IMO.
The Sun's rotation allows the superheated elements/gasses within it to spin into astral bodies, IE proto planets.
We see this with Mercury and Venus, as they resemble miniature stars on a lot of levels.
Eventually, the distance from the sun combined with electromagnetic forces causes the gasses to become liquids, then eventually solids, allowing for the formation of organic life.
The Earth, 3rd Planet from the sun, has cooled enough over time in order to produce a great deal of both liquid and solid matter in order to support life.
Mars, sadly, lost its atmosphere, most likely due to ancient species destroying their own planet out of greed and insanity.
Eventually, the core of the planet, still filled with its star, expands to have enough space to allow people to live inside the planet itself, allowing people to escape the calamities and solar radiation of the surface world.
So, in effect, over time, Planets more or less become spaceships:
We live on the outside, and then migrate into the inside as the outside deteriorates, and then live on the inside of the planet once the outer atmosphere is destroyed due to the Planet naturally distancing itself from the Sun.
Nature is designed very well, it's sad some fools want to mess up the design just to pretend they're superior.
