Answer:
In Nebular Theory, the Sun originated in a Nebula. It would have collapsed gravitationally (the particles of the Nebula began to gather and compress). This causes increased gravitational attraction which in turn causes more matter to come together and vice versa.
Due to compression, the center of the nebula heats up and begins to glow. Proto-Sol is formed. By this time we would no longer have a disorganized heap of gas and dust and would have a discoid structure with a thickening in the center. Then the accumulation of matter continues, which will lead to the onset of nuclear reactions that allow the newly formed star to resist gravitational pressure.
The remaining gas and dust begin to cluster in small areas around the star forming the planetesimals (small rocks) which in turn cluster to form the proto-planets (primitive planets). In the area closer to the sun, where temperatures were higher, condensation of matter occurred which led to the formation of telluric planets, terrestrial or interior. In the farthest area, where the temperature was lower, condensation of matter more similar to that of the star occurred forming the giant or outer gas planets.
