1. The Birth of a Solar System
The history of our Solar System began about 13.7 billion years ago with the Big Bang creation event. This provided the elements, along with later material from former stars, to form the solar system.
Scientists now believe that our Milky Way galaxy was formed very early in the history of the Universe, perhaps as early as 950 million to 1 billion ABB. Our solar system, however, took another 8 billion years or so to form.

2. The Protoplanetary Disk Model
A protoplanetary disk is a circumstellar disk of matter, including gas and dust, from which planets may eventually form or be in the process of forming.

3. The Protoplanetary Disk Model
The existence of such disks was long suspected, but was confirmed by direct imaging in 1994 when C. Robert O'Dell and colleagues of Rice University used the Hubble Space Telescope (HST) to examine newborn stars in the Orion Nebula. About half of those were found to be surrounded by disks of gas and dust.

4. The Protoplanetary Disk Model
Also in 1994, John Stauffer and associates of the Harvard-Smithsonian Center for Astrophysics reported that 70 to 80 percent of infant stars at the center of the Orion Nebula showed signs of having disks.
This high fraction has since been confirmed by more sensitive observations by the Infrared Space Observatory. 

5. The Protoplanetary Disk Model
A large, rotating nebula began to form. As a result of gravitational contraction, the spin rate increased. Most mass concentrated in the central proto-star. The remaining material formed an accretion disk. The material in the accretion disk began to clump. The nebula began to contract about 5 billion years ago.
The heavier elements were formed in many earlier stars and supernovas.
Dust, gas and chemical compounds began to concentrate in a region of space.
Supernova shockwaves helped to “clump” the matter.
The protosun became a star. The solar ignition flare-up may have blown away the hydrogen and helium atmospheres of inner planets. The protoplanets heated, separating heavy and light minerals. Larger bodies cooled slower, with heavy materials settling over longer times into central cores.

6. The Protoplanetary Disk Model

7. The Protoplanetary Disk Model