The History and Future of the Solar System

The Solar System was just sparse amounts of gas 5 billion years ago, Hydrogen and Helium were the main components (Approximately 2% were heavier elements left from another star).  The pre-solar-system nebula collapsed and began to spin.  Then, as more mass condensed at the center, gravity's effects began.  Then, over millions of years, density and energy heated the Sun's core.  Meanwhile, collisions between small, asteroid-like objects formed the first proto-planets.  Then, the Sun's core reached 18 million degrees, and Hydrogen fusion started.  The expulsion of energy and radiation cleared the inner solar system of debris, save the now fairly large proto-planets.  The extra gas ended up orbiting around the outer planets, forming the Gas Giants.  All remaining planetary objects were absorbed by the Gas Giants, turned into tiny moons, propelled back into the soon-to-be asteroid belt, or sent out into the Kuiper Belt or Oort Cloud.  Eventually all planets had "cleared their neighborhood", a term that means to eject all matter form their orbital paths with gravity.  No changes occurred for billions of years afterward, bringing us to the present.

 The Solar System is now 4.6 billion years old.  Every 1.1 billion years, the sun grows slightly larger, and increases by 10% in luminosity.  Within one billion years, the radiation from the Sun will become so powerful that all life on Earth will go extinct, and Mars will be the most habitable planet.  In 5 billion years, the Sun will swell to a red giant and swallow Mercury, Venus, and Earth.  Then, in an explosion the Sun will shed its outer layers into space and become a white dwarf (white dwarfs and other stellar explosions are explained here), and shortly after cool and become a black dwarf.  The frozen planets may orbit into eternity or the explosion of the Sun will send them into space.  Then, the gas from the Sun may help make new stars and planets, maybe for billions of years to come.