Unit 6 Lesson 4 What Are the Planets in Our Solar System? Copyright Houghton Mifflin Harcourt Publishing Company

Transcription

1 Unit 6 Lesson 4 What Are the Planets in Our Solar System?

2 What other objects are near Earth in this part of space? Earth and millions of other objects make up our solar system.

3 In Our Corner of Space A solar system is made up of a star and the planets and other bodies that revolve around it. The sun is the star at the center of our solar system.

4 In Our Corner of Space Our solar system contains eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. A planet is a large round body that revolves around a star in a clear orbit. *Clear orbit means that the orbit of a planet does not cross of another body

5 What about Pluto? Pluto was once classified as a planet but is no longer. Astronomers refined the definition of a planet to include a clear orbit. Pluto s orbital path crosses that of Neptune. Its now classified as a dwarf planet. Dwarf planets are nearly round bodies whose orbits cross those of other bodies.

6 What about Pluto? Dwarf planets are nearly round bodies whose orbits cross those of other bodies.

7 Asteroids An asteroid is made of rock and metal. Most asteroids are in the asteroid belt between Mars and Jupiter.

8 In Our Corner of Space A comet is a ball of rock and frozen gases that orbit the sun in the areas at the edge of the solar system. Distances are measured using the astronomical unit, or AU. One AU is the distance between Earth and the sun about 150 million km.

9 In Our Corner of Space Planets in the solar system are divided into two groups The inner planets are those closest to the sun: Mercury, Venus, Earth, and Mars. Earth is the largest and the densest of the inner planets. The outer planets are those farthest from the sun: Jupiter, Saturn, Uranus, and Neptune. These planets are the largest in our solar system.

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11 Planets Near and Far. After the sun had formed, a cloud of rock, dust and gas remained around it. The planets in the solar system were formed from these leftover materials. The part of the cloud closest to the sun was also the warmest. In this area, rock and metal bits clumped together to form the rocky bodies that became inner planets. The outer solar system was much colder. Gases formed icy particles in the extreme cold. The cold gases and icy particles clumped together to form huge balls of gas and ice that became the outer planets.

12 Planets Near and Far The inner planets: Have small diameters and thin atmospheres. Are the smallest and warmest planets. They have hard surfaces made of rock. The inner planets revolve around the sun more quickly than the outer planets do. The inner planets are the only planets where probes from Earth have landed. A space probe is a robotic space craft that leaves Earth orbit and explores space.

13 Planets Near and Far The outer planets: Are larger and less dense than the inner planets are. Are giant balls of gases with very small, solid cores. Rotate quickly, which makes for a short day; however, these planets take a long time to revolve once around the sun. Therefore, they have short days but long years. Unlike the inner planets, the outer planets have rings.

14 Planets near and far

15 Planets near and far

16 The Inside Track Inner planets are alike in some ways. 1. They are all small and rocky 2. They have few moons or none. But, still each planet is unique.

17 Mercury Mercury has a thin atmosphere of carbon dioxide with a surface like our moon.

18 Venus Venus has a thick carbon dioxide atmosphere, which makes it boiling hot. Drops of acid fall from its clouds.

19 Mars Mars is dry and freezing cold. Huge dust storms blow across Mars s surface. Thin atmosphere of carbon dioxide.

20 The Inside Track Only Earth has water, soil, and air to support life.

21 The Inside Track

22 The Outside Track (What do You know?) The outer planets are very different from the inner planets. These huge planets do not have solid surfaces. They are also called gas giants, because they are made mostly of gases. They all have many moons and are surrounded by rings made of dust, ice, or rock.

23 The Outside Track

24 Jupiter Fun Facts Jupiter is the largest planet in our Solar system. It is so big that more than 1300 Earths could fit inside it. Jupiter has many storms raging on the surface, most notably the big red spot which is the largest hurricane in our Solar System.

25 The Outside Track Jupiter and Saturn are the largest planets in our solar system.

26 The Outside Track: Uranus

27 The Outside Track Neptune is the farthest planet in the solar system, its about 30 AU away. From space, Neptune s atmosphere looks blue. Sometimes, white clouds of methane ice crystals blow high across this planet.

28 The Outside Track

29 The Right Spot Out of the eight planets in our solar system, only Earth has life as we know it. Why?? Scientists think Earth is the only planet within the life zone. The life zone is the region of space where the temperature range allows life to thrive. Our solar system s life zone begins just outside Venus s orbit and ends before the orbit of Mars. If Earth were outside this life zone, it would be either too hot or too cold for life to exist on our planet.

30 The Right Spot Our moon is within the life zone but does not have life. Why?? It doesn t have an atmosphere or liquid water. Earth s atmosphere does many things to support life:??? such as trapping solar energy to keep Earth s temperature comfortable. Earth s atmosphere contains the gases most living things need, and it protects living things from harmful solar radiation.

31 The Right Spot Earth s Oceans help maintain the earth average temperature at about 13 C. How??? Earth s oceans store and distribute heat from the sun. Ocean currents carry heat away from the equator and release heat near the poles. Without the oceans to store and distribute heat from the sun, some places on Earth would be extremely cold or extremely hot.

32 The Right Spot

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