STAR FORMATION
The Sun is a star. All the stars in the sky are basically the same as the Sun, the only reason that the Sun is so much bigger and brighter than the stars is that it is so much closer.
Stars are formed inside large clouds of gas and dust called nebulae. They consist of Hydrogen, Helium and various heavier elements and complex molecules and cover many light years. If the material in the nebula is disturbed, for example by a nearby exploding star, parts of it will begin to collapse. This will form a collapsing sphere of material about a light year across. As the collapse continues the interior of the sphere will warm up resulting in a dense core some millions of kilometres across surrounded by a disk of material billions of kilometres across. A dense fog of dust and gas surrounds the structure hiding it from view.
When the core becomes sufficiently compressed and the internal temperature reaches tens of millions of degrees nuclear reactions start with Hydrogen being turned into Helium releasing energy. The release of energy heats the object further, it begins to shine and a star is born. Once the nuclear reactions begin they create outward pressure and prevent the new star from collapsing any further.
Material streams away from the star creating a stellar wind which pushes away the nearby dust and creates a cavity in the surrounding nebula. At this stage the star often has two jets of material shooting away from its north and south poles.
