Dust particles within the solar nebula will often coalesce into matter conglomerates referred to as planetesimals.  The formation of the planetisimals is a process that requires roughly a few million years.  In the case of planetisimal formation, the dust particles are held together by gravitational and electrostatic forces.  Gravitational forces allowed planetisimals collided and formed larger masses called protoplanets.  This gravity-induced accumulation of matter is referred to as accretion.  Inner protoplanets will accumulate material by means of accretion and this material will tend to have high condensation temperature.  The impact energy and the natural decay of elements will melt the solid material and so inner planets will start their existence as spherical accumulations of molten rock.  Due to a disparity in density, more dense material will sink into the center of the protoplanet.  This will inevitably coerce less dense material to the surface. 

            Outer protoplanets are formed in a similar manner.  The only main distinction is the location of the protoplanet will affect the material.  The cores of protoplanets can be rocky but due to the accumulation of dust particles, the net energy would be enough to vaporize excess ices, therefore the outer planets would be composed of mainly gases.

            During the duration of planetary formation, the protostar’s center will reach temperatures that are high enough to initiate thermonuclear reactions.  Once the nuclear reaction has started, the protostar becomes a star.  Once a newborn star starts its life, the force of the nuclear reactions from within the stellar core will be enough to expel the outer layers of the star out into space.  This loss of mass in initial star stages is referred to as the T Tauri Wind (sidenote:  the name is in reference to the star found in Taurus in which this event was first observed).  The T Tauri Wind is important in the fact this will sweep the rest of the solar system area of excess materials so that the accretion of material will be stopped.  Matter loss (such as the T Tauri Wind) is common in stars even after the initial T Tauri Wind.  Usually, matter loss will take place in the form of solar wind which consists of high speed protons and electrons emancipated from the star’s outer layers.