1. Outer Planets

2.  The outer planets are called Jovian or Jupiter- like.  Made of gas and are several times MORE massive than the Earth.  Grew to present size in about 10 million years.  When studying outer planets you must take into account their SIZE and POSITION.

3.  Jovian planets formed mainly from the GAS in the solar nebula.  Rotating gas and dust of solar nebula became unstable and formed the outer planets by direct gravitational collapse.  Form from the gas without first forming a dense core by accretion.

4.  The Jovian planets formed in the outer solar nebula  Lower temperatures allowed the gas to form large amounts of ice. (Three times more ices than silicates for inner planets)  The Jovian planets then grew rapidly and became massive.  Had enough gravity to attract large amounts of nebular gas and so a large amount of helium and hydrogen

6.  The four Jovian planets may have formed closer to the sun in the same area  Where Jupiter and Saturn currently are  Gravitational interactions shift Jupiter slightly inward and Saturn slightly outward.  Event forces Uranus and Neptune to migrate rapidly outward to their present orbits.

7.  Migration would have happened over many millions of yrs.  It effected smaller objects dramatically. 1. pushed the Kuiper belt objects to larger orbits. 2. flung many planetesimals into highly elliptical orbits, and they hit planets.

8.  Jupiter grew massive and due to position, gravitationally disturbed the motion of close by planetesimals.  These bodies should have formed a planet but were thrown into the sun or out of the solar system.  The asteroids we see today are the last remains of the rocky planetesimals.

9.  Comets are the last of the icy planetesimals.  Some comets formed in the outer solar nebula beyond Neptune.  Many comets were ejected far into the outer solar system by the massive Jovian planets

10.  Large satellite systems of the Jovian planets contain two kinds of moons. 1. Moons formed in orbit around the forming planet. 2. Moons may be captured planetesimals and asteroids.

11.  A large mass makes it easier for a planet to hold onto orbiting ring particles.  If farther from the sun, the particles are not as easily swept away by the pressure of sunlight and the solar wind.  Reason why no rings are around inner planets and are found around outer planets.