In another model
Jupiters help Earths to take shape. The leftovers from the first
giant gas planets to form from the disk of gas and dust provide
raw material for smaller, rockier planets to form by Accretion.
Gravel and rocks clump together to form hundreds of planetary embryos
about the size of Earth’s moon.
Jupiter’s gravitational pull causes
these planetary embryos, which would otherwise remain in their individual
courses, to collide and, smashing into each other, they grow to
form a handful of Earth and Mars-size planets.
This third model acknowledges the formation
of the gas giants first, then rock planets later, as opposed to
all the components of the system forming simultaneously - so the
sequence is different. But it still builds on the understanding
that they all form by Accretion, and generally fixed in their orbits.