The Planets of our solar system Part Two: Outer Gas Giants

Jupiter -778,330,000 Km from the Sun -Diameter = 143,000 Km (Largest planet in the system) -4th brightest object in the sky (after the Sun, Moon and Venus) -Made mainly of gas (minimal liquids and solids): 90% H, 10% He and other trace elements -Multiple visible bands of high velocity winds, a giant “Red Spot” existing for 100’s of years, represents a high pressure region -Has a massive magnetic field that extends 7 million Km in all directions -Orbits the sun once every 11.86 Earth Years -Rotates on its axis once every 9.8 hours -318 times the mass of the Earth but ¼ of the density (1.33) -Surface Temperature range = -145°C to 21°C

Jupiter’s Moons Jupiter has 60+ moons and counting. It’s four largest satellites were first discovered by Galileo in 1610. Ganymede – Largest moon in the solar system (6,260km in diameter) and the only moon with it’s very own magnetic field. Callisto – The most heavily cratered object in the solar system. This mixture of rock and ice is 4,800km in diameter Io - Most volcanically active body in the solar system. Its surface is covered by sulfur in different colorful forms. 3,600km in diameter Europa - Water ice surface, which may be covering an ocean of water or slushy ice. Best candidate for life in the solar system. 3,140km diameter

Saturn -Second largest planet with a 120,536 km diameter -Nearly 1.5 billion km from the Sun -Very similar chemical composition as Jupiter -Polar flattening =.10 (very oblate) -”Banded” like Jupiter, but mostly known for its profound Ring System, first noticed, but not understood by Galileo -Density = 0.7 (It would float on water!) -95 times the mass of Earth -Orbits the Sun once every 29.5 years -Rotation period is around 10.5 hours -Most distant planet that can easily be seen with the average un-aided eye -Very fast winds (measured at 1,800 km/h) -Dense and very hot rocky core, very cold surface

Saturn’s Rings and Moons Ring’s- First explained by Christiaan Huygens in 1655 and noticed to be many separate rings by Giovanni Cassini in 1675. They are actually small bits of ice and rock and are less than 1km thick although they span 250,000 km! These rings are thought to be relatively young – perhaps the remains of a previous moon or moons. Saturn has over 34 named moons, but the largest and most well known of them is Titan. At 5,050 km in diameter, it is the 2nd largest moon in the solar system. It is the only moon with a substantial atmosphere and is thought to have an environment resembling pre-life Earth.

Uranus -Orbits at an average of 2.8 billion km from the Sun -Over 51,000 km in diameter -Mistaken for a “star” until 1781 -Named after the ancient Greek god of the heavens - Its axis is tilted 90° (north pole faces the Sun!) -Distinctive blue color is a result of methane gas in the upper atmosphere -Has 11 faint dark rings -Coldest atmosphere of any planet -Orbits the sun once every 84 Earth years -Solar Day = 14 - 17 hours -Lack of internal heat leaves the surface relatively “quiet” compared to it’s neighbors Uranus’ 5 largest moons: Miranda, Ariel, Umbriel, Oberon and Titania (1560 km diameter)

Neptune -8th planet of the solar system -Cloudy atmosphere and deep blue color due to Methane ice crystals -49,500 km diameter -Fastest winds of the solar system (2,000 km/h) – the Great Dark Spot has since vanished. -4.5 billion km away from the sun -Average temperature is -200°C -Watery surface, Hydrogen and He atmosphere -Radiates twice the amount of energy it receives from the Sun -17.1 times the mass of the Earth -19.2 hour rotational period, 165 year revolution There are 8 known moons of Neptune, all are smaller than Earth’s Moon. The largest (2,700 km diameter) is Triton. Triton has geysers that shoot Nitrogen 8km into the sky!