The origin of solar system is a topic that has been discussed with much enthusiasm through the ages. Nothing has been set down for certain, but conjectures abound.
It has been theorized that the solar system had its beginnings in a cloud of interstellar gas or dust. Something disrupted this “solar nebula” and it collapsed under its own gravity. A supernova taking place nearby may have been one such disturbance. The collapsing nebula compressed in the center and heated up so much so that the dust vaporized. This is thought to have taken less than 100,000 years to happen.
The compressed center eventually became dense enough to form a “proto-star” around which the rest of the gas flowed. The gas also added to the mass of the star when it flowed inwards, but didn’t actually reach the star due to the centrifugal forces involved. The gathered gas formed an accretion disk around the star, eventually cooling down.
The origin of solar system continued with the condensation of metal, rock and ice precipitated by the cooling gas. The metal formed almost simultaneously with that of the accretion disk while rock took longer to condense. Meteorite isotope measurements have estimated this to have taken place 4.55-4.56 billion and 4.4-4.55 billion years ago. Dust particles that collided with each other formed larger particles that eventually became boulders or small asteroids.
A particle large enough to achieve non-trivial gravity quickly drew in smaller particles into its own orbit. The size to which the particle eventually grew was dependent on its distance from the star and the composition and density of its own nebula. Planet formation is thought to have been dependent on its distance from what would eventually become the sun, with the planets on the outermost edge of the solar system taking the longest to form.
The cooling nebula would have generated a powerful solar wind as it cooled, which would have swept away the gas surrounding it. A proto-planet that was large enough would have pulled the nebular gas and form a gas giant. Otherwise, the proto-planet would remain an icy or rocky body. These proto-planets and gas giants collided with one another and formed large celestial bodies, in stable orbits and the solar system we study today. Despite the theory, unanswered questions remain: how quickly did these “proto-planets” form and how large were they?
Origin Of The Universe