ByBryan Nisbet

Inner vs. OuterPlaners

Inner Planets• Also called terrestrial planets• Few moons• No ring systems• 3 of the 4 have atmosphere• Has an asteroid belt

Outer Planets

• Jovian Planets• 99 percent of the mass known to orbit the Sun• Jupiter and Saturn consist overwhelmingly of hydrogen

and helium• Uranus and Neptune possess more ices in their

makeup• All four gas giants have rings• They have comets– Typically only a dew kilometers across

Inner vs. Outer• The inner planets (those planets that orbit close to the sun) are quite

different from the outer planets (those planets that orbit far from the sun).• The inner planets are: Mercury, Venus, Earth, and Mars. They are relatively

small, composed mostly of rock, and have few or no moons.• The outer planets include: Jupiter, Saturn, Uranus, Neptune, and Pluto (a

dwarf planet). They are mostly huge, mostly gaseous, ringed, and have many moons (again, the exception is Pluto, the dwarf planet, which is small, rocky, and has one large moon plus two tiny ones).

• Generally, the farther from the Sun, the cooler the planet. Differences occur when the greenhouse effect warms a planet (like Venus) surrounded by a thick atmosphere.

• As the planets orbit the Sun, they travel at different speeds. Each planet speeds up when it is nearer the Sun and travels more slowly when it is far from the Sun (this is Kepler's Second Law of Planetary Motion).

Why Pluto isn't a Planet

• Pluto is not a planet because it is way too small, and it doesn't meet the necessary requirement needed to be a planet.– The requirements are:• has sufficient mass to assume hydrostatic equilibrium (a

nearly round shape), • is in orbit around the Sun, • has "cleared the neighborhood" around its orbit.