SOL 4.7 Earth/Space Systems & Cycles NOTEPAGE FOR STUDENT Page 1 The Solar System: The Planets Our solar system, located in the Milky Way galaxy, is ancient! Our solar system is home to eight planets, a number of dwarf planets, 170 named moons, thousands of asteroids and comets orbiting the sun as well as gas and dust. Let’s check out the eight planets of our solar system! Our solar system has eight planets. A planet is defined as having a round body (shaped that way because of its own gravitational force); it must orbit, or revolve around the Sun; and it must have its own unique orbit that no other bodies in space can influence. Even though the chart will let us see the planets in order, it will still be difficult to imagine the space between the planets and the sun. Our solar system is huge! There are two types of planets: terrestrial and gas giants. A planet that is largely made up of rock is called terrestrial. The terrestrial planets are Mercury, Venus, Earth, and Mars. The large planets in our solar system that are made up of gas are called the gas giants. The gas giants are Jupiter, Saturn, Uranus, and Neptune. Mercury, the closest planet to the Sun, is heavily cratered and looks like Earth’s moon. Since Pluto has now been reclassified or redefined as a dwarf planet, Mercury is now our solar system’s smallest planet. Venus, the second planet from the Sun, is similar to Earth in size and mass. Because it is covered with permanent blanket of clouds, the surface of Venus is hot enough to melt lead. Earth, the third planet from the Sun, has factors which create the perfect conditions for life, such as its atmosphere, distance from the Sun, and the presence of liquid water. Mars, the fourth planet from the Sun, has a thin atmosphere as well as a wide network of canyons and river beds. Mars is called the red planet. Scientists believe that Mars may have once had a warm, wet Earth-like climate. ©2011 SOL 4.7 Earth/Space Systems & Cycles NOTEPAGE FOR STUDENT Page 2 The Solar System: The Planets Jupiter, the fifth planet from the Sun, is our solar system’s largest planet. It is considered a gas giant. Jupiter has no solid surfaces. Saturn, the sixth planet from the Sun, was considered by early scientists to be the only planet with rings. Scientists have since discovered rings around all of the gas giants – that means that Jupiter, Uranus, and Neptune have rings as well. Uranus, the seventh planet from the Sun, is a gas giant. Neptune, the eighth planet from the Sun, is a gas giant that appears blue through a telescope. Pluto used to be classified as a planet, but scientists have learned that Pluto doesn’t have its own unique orbit. It shares space with other objects in its orbit. As a result, Pluto is now called a dwarf planet. Planet Diameter Chart Planet (in order based on Diameter (in miles) Rank in Size their position from the Sun) 3,032 (Smallest) 8 Mercury 7,521 6 Venus 7,926 5 Earth 4,222 7 Mars 88,846 (Largest ) 1 Jupiter 74,898 2 Saturn 31,763 3 Uranus 30,778 4 Neptune ©2011 .