Outer Planets

Outer Planets

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.

Formation Idea- 1 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.

Formation Idea- 2 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

Jupiter layers

Position (orbit migration)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.

Orbital Migration cont.

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.

Effects of positionasteroids

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.

Effects of positioncomets

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

satellite (moon) systems

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.

Ring systems

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.