There seems to be 2 theories going around:
1) the solar nebular/Kant model where a big gas cloud collapsed down into a disk with the Sun at the centre and the planets forming from accretion of the remaining materials in the disk; or
2) the gas cloud just collapsed down into the Sun - which, when it reached a critical density and fusion took off in its core, underwent a violent hiccupy sort of explosion throwing out lots of matter which was what accreted down to form the planets.
I had thought scientific consensus was pretty much aligned with theory 1), but have recently seen 2) espoused in some seemingly authoritative places.
Welcome comments. If 2) is prevailing theory, what was the nature of the outflung material? Had it undergone any fusion itself in the "hiccupy sort of explosion"?