1. Planets

2. What’s in Our Solar System?

3. The Sun The Sun’s age is about 5 billion years. Its energy comes from nuclear fusion (where hydrogen is converted to helium) within its core. This energy is released from the Sun in the form of heat and light. Stars are the only solar bodies that generate their own light. Very bright planets, such as Venus and our moon, appear bright because they are reflecting sunlight. Remember: Stars produce light. Planets reflect light. Our sun is classified as a yellow main sequence star. A star’s temperature determines its “color.” The coldest stars are red. The hottest stars are blue.

4. Geocentric vs. Heliocentric Theory Geocentric Theory (or “Ptolemaic” Theory – pronounced “Tole-ah-may-ic”) is an ancient view of the universe based primarily on religion, philosophy, and mathematical ideals that Earth is the center of the universe and all other planetary bodies revolve around the Earth. The Greek scientist first believed in this model.

5. Geocentric vs. Heliocentric Theory Heliocentric Theory (or “Copernican” Theory) is a revised view of the universe based on the studies of Nicholas Copernicus, who was a mathematician in the 1500’s. Belief that the Sun is the center of the solar system. Galileo also believed in this system.

6. How many planets are there in the Solar System 1.There are 8 planets in the Solar system Gravity holds the planets and other objects in their orbits.

7. The 8 Planets of the Solar System Planets are categorized according to composition and size. There are two main categories of planets: –small rocky (terrestrial) planets (Mercury, Venus, Earth,and Mars) –gas giants (Jupiter, Saturn, Uranus, and Neptune)

8. The Relative Size of the Planets in the Solar System

9. Characteristics of Small Rocky Planets They are made up mostly of rock and metal. They are very heavy. They move slowly in space. They have no rings and few moons (if any). They have a diameter of less than 13,000 km

10. Mercury Mercury is the 1 st planet from the Sun. Mercury has many craters like our moon. The core began to cool and condense or get smaller. There is no atmosphere on Mercury. It all escaped. Temperatures on Mercury are from -183 to 427 C Mercury has no moons. Mercury’s rotation is 176 Earth Days Mercury’s revolution is 88 Earth Days

11. Venus Venus is known as the Earth’s Twin The Surface is volcanic and rocky The atmosphere of Venus has a large amount of carbon dioxide gas. Carbon dioxide traps heat in Venus’s atmosphere, causing the surface temperatures to increase greatly. We call this effect the Greenhouse Effect. The temperature of Venus is 457 to 482 C Venus rotation is 243 Earth Days Revolution is 225 Earth Days Venus has no moons. It has thick yellowish clouds composed of sulfuric acid driven by fast winds. Its surface is dry and dusty with craters, mountains, and volcanoes.

12. Earth Earth is the only planet known to support living organisms. Earth’s surface is composed of 71% water. –Water is necessary for life on Earth. –The oceans help maintain Earth’s stable temperatures. –Water is a primary cause of Earth’s surface weathering. Earth has a distinct atmosphere. –It helps screen harmful radiation from the sun. –It prevents meteorites from reaching Earth’s surface. –It traps heat to help maintain Earth’s stable temperatures. Earth has one moon.

13. Mars is red because of the iron ore found on the planet. Mars has permanent ice caps at its poles. The ice caps are composed mostly of frozen carbon dioxide (what we call “dry ice”). Mars has the largest volcano in our solar system: Olympus Mons. Olympus Mons is approximately 24 km high (15 miles). Atmospheric is thin Carbon Dioxide Temperatures on Mars range from -183 to 427 C Mars has two moons: Phobos and Deimos Mar’s rotation is 1.02 Earth Days Revolution is 686 Earth Days Mars

14. Pluto Pluto is the only planet not visited by spacecraft. We are not sure of its composition. Based on current data, scientists believe it is a small, rocky planet. Pluto seems to lie on its side: its equator points straight up, and one of its poles points directly at the sun. Pluto has only one moon (Charon). Pluto’s moon is half the size of Pluto itself, which is unusually large for a moon. Because they are so close in size, sometimes Pluto and its moon are considered to be a double planet system. Pluto was located and named in 1930.

15. Characteristics of Gas Giants They are made up mostly of gases (primarily hydrogen & helium). They are very light for their size. They move quickly in space. They have rings and many moons. They have a diameter of less than 48,000 km

16. Jupiter Jupiter is composed almost entirely of hydrogen and helium. It is thought to have a small rocky core. Jupiter is the largest planet in our Solar System Jupiter’s largest moons are Io, Europa, Ganymede, Callisto. Rotation is 10 Earth hours Revolution is 12 Earth years. Jupiter’s characteristic Great Red Spot is an enormous storm, consisting of a spiraling column of clouds big enough to contain three Earths. The clouds are colder than the surrounding areas, and so the Great Red Spot sits about five miles above the upper cloud layer. Jupiter has 63 known moons.

17. Saturn Saturn, like Jupiter, is composed almost entirely of hydrogen and helium. Small and rocky core. Saturn has many rings composed primarily of ice with some ice-coated rocky particles. Saturn’s rings are very wide (but very thin (less than 1 mile thick). Saturn has 52 known moons, some of which orbit inside the rings!

18. Uranus Uranus has 27 moons Has 11 dark rings surrounding it. The whole planet does not have a core but is made of rock and ice. Uranus is tilted on its axis at 98 . Because of its strongly tilted axis of rotation, Uranus essentially spins on its side as it orbits the sun. Scientist believed something smashed into Uranus to tilt it. Uranus is blue in color due to methane gas in its atmosphere. Rotation is 17.9 Earth hours Revolution is 84 Earth Years

19. Neptune Neptune is also blue in color due to methane gas in its atmosphere. Neptune has a Great Dark Spot in its atmosphere. The Great Dark Spot is a huge storm the size of Earth. Under the atmosphere it is made of rock and various types of ice. 13 moons and several rings Rotation.67 Earth Days Revolution 164 Earth Years