ELi5 what makes the sun a star and not a planet? And why is the moon not considered a planet?
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Stars are currently (or previously) undergoing fusion, this is what gives the sun the energy to be the big bright ball in the sky. Stars are large because they rely on their own gravity to squeeze the hydrogen and cause the fusion. The smallest stars are about 10x larger than Jupiter.
Planets are things which orbit a star, are round, and have pretty much cleared out their orbit. This last bit is so that Ceres (biggest asteroid) isn’t a planet, otherwise it would be.
Dwarf planets are things that directly orbit a star, are round, but may not have cleared out their orbit. This is stuff like Ceres and Pluto and Eris and all the far out little Plutoids.
Moons are rocks which orbit a planet, that’s basically the end of their criteria list. Jupiter has moons which range in size from Ganymede (2.5% the mass of Earth) all the way down to Valetudo which is just 1km in diameter. If it orbits a planet and its natural, its a moon!
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