The Process of Accretion

Most of the first stars that condensed from the hydrogen and helium formed in the cosmo-genesis ( Big Bang ) were massive stars because these gases were very dense.  In the nuclei of these stars protons ( hydrogen nuclei ) were fused together by pressure exerted on the nucleus by the overlying layers of gas and helium was formed at the reigning temperature of 15 million degrees Centigrade.  0,07% of the mass of the protons was converted into energy in the form of gamma rays at a frequency of 10²⁵.  As this energy was radiated it was constantly absorbed and re-emitted by surrounding protons and electrons and by the time the energy reached the surface ( after some millions of years ) the frequency had dropped to 10¹⁴, i.e. it had become visible light.  Because of their great masses, these stars very quickly used up such a percentage of their hydrogen fuel that their production of energy suddenly decreased so that they collapsed under the weight of the overlying layers of gas.  Then a rebound took place and these stars were blown to smithereens in supernova explosions.  Besides converting hydrogen into helium, some heavier elements were formed, such as carbon, oxygen and nitrogen.  No atoms heavier than iron can be formed by fusion.  But the tremendous temperature and pressure in the explosion formed other atoms with nuclei heavier than iron.  The exploded material now contained about 1% of atoms heavier than hydrogen and helium.  These supernovae took place about 9 milliard years ago ( 9 thousand million ).  This material became the matter from which the second generation of stars was formed - the finely-divided matter packing together.  These new stars underwent a similar lifestyle until they, about 5 milliard years ago, also went supernova.

 clockwise direction and in the second case in a counterclockwise direction.  In rare cases the point of contact would be directly behind, thus speeding up without causing any spin.  As this process went on, the particles grew bigger and bigger.  It seems that the counterclockwise spin became twice as prevalent as the clockwise spin as only three of the planets spin clockwise ( Venus, Uranus and Pluto ) while the other six spin counterclockwise as seen from the north. 

If we view the particles from the side, the place of revolution, we see that the axes of spin of the particles were also subject to being tilted from the vertical to the plane of revolution, depending upon how many particles struck the leading particles above or below their equators.  The axis of spin of Neptune grew to a value of 29º33’;  Saturn 26º43'; Mars  25º12'; Earth  23º27'.  The tilt of the axis of spin of Jupiter reached only 3º7' while that of Mercury remained zero.

The surfaces of the Moon and Mercury bear silent testimony of the end results of the process of accretion.  Most of the craters on the side of the Moon facing the Earth that are greater the 10km have a diameter of 48 kilometres.  To form a crater of this size requires a clump of material eight kilometres in diameter.  The smaller clumps of aggregated material were loosely packed, but as the clumps became bigger, they became more solid.  With no atmosphere or water, Mercury and the Moon retained their surfaces as they were when the process of accretion came to an end.

G W Wetherill ( Scientific American, October 1969 ) explained how he started with a model containing 100 clumps ( planetesimals ) and allowed them to revolve around a protosun.  His model showed that after 30,2 million years, the 100 planetesimals would have accreted to 22 planetoids;  and after 79 million years to 11.  After 100 million years there were only 4 planets, showing that the Sun’s 4 inner planets could have condensed in only 100 million years.

The axis of rotation of Mercury remained vertical because of the great force of gravity exercised by the Sun which kept the particles crashing into Mercury very confined to the plane of revolution.

The great mass of Jupiter probably obviated its axis from being tilted.  But the planet Uranus poses a very difficult problem.  Not only has the axis of rotation of Uranus been tilted by an angle of 97° 53', but the planet’s 5 large moons also revolve in a plane tilted to the plane of revolution by the same angle.  This cannot be explained away by postulating a collision because the ellipses in which those 5 moons revolve are of very low eccentricity - they are nearest to circles of all the orbits in the Solar System.  The most eccentric of the orbits of the five moons has an eccentricity of only 0,005.  The eccentricity of the orbit of our Moon, by contrast is 0,0549 or ten times greater.  The whole Uranian system must have had this configuration since the beginning.  Perhaps Uranus developed at a very great speed of rotation so that it cast material off from its equatorial plane and this materiel subsequently condensed into five moons.  The rings outside the furthest moon also revolve in this plane tilted at 97° 53'.

The retrograde revolution of the two moons of Neptune, Triton and Nereid, and the furthest away moon of Saturn, Phoebe, are most probably captured bodies.

The other moons in the Solar System were formed by accretion of material that revolved around the planets as they formed in the disc.

The thousands of Minor Planets all revolve counterclockwise around the Sun and they were also formed by accretion but were prevented from forming one large planet by the resonances that their orbits developed with the orbit of Jupiter as shown by the Kirkwood gaps at resonances of 2:1;  3:2;  5:2.