Why don't the Sun's gases spread outwardly?

As many other answers have said, the sun is held together by gravity. As a hydrogen atom rises towards the surface, it slows down like any other rising projectile. read more

Think of the sun and its planets all as proto spheres of matter pre birth of our sun. Gas and heavier elements attracted to each other by gravity. read more

Gas molecules move slow, and owing to the planet's massive size (and therefore higher gravity), get captured. Just like the proto-Solar system and the proto-Sun, gas giants can keep accreting gas till they induce a gravitational collapse. read more