What Makes Up the Solar System?

1. Unit 5 Lesson 2 What Makes Up the Solar System?

2. Vocabulary • SolarSystem: A star and all the planets and other objects that revolve around it. • Planet: A body that revolves around a star. • Satellite: A body in space that orbits a larger body. • Asteroid: A piece of rock and metal that orbits the sun. • Comet: A ball of ice, rock, and frozen gases that orbits the sun.

3. What Makes Up the Solar System? Where is Earth located in our solar system? Where is Earth located in our universe? Scientist explain that the sun is the center of the solar system. All the planets in the solar system, including Earth, revolve around the sun. The solar system is located on the edge of the Milky Way Galaxy, one of millions of galaxies in the universe.

4. The Inner and the Outer Planets • Astronomers generally divide the planets into two groups, the inner and outer planets. The inner planets – Mercury, Venus, Earth, Mars – are rocky and are usually much smaller than the outer planets. • The gas giants – Jupiter, Saturn, Uranus, and Neptune – are not as dense as the inner planets. They have thick atmospheres consisting mostly of hydrogen, helium, methane, and ammonia. Pluto is the exception among the outer planets, as it is rocky and very small.

5. The Inner and the Outer Planets • Because of the distances of the planets from the sun is so great astronomers use the astronomical unit (AU) to measure distance. An AU is the average distance between Earth and the sun (150 million km, or about 93 million mi).

6. The Inner Planets • The four inner planets are Mercury, Venus, Earth and Mars. All the inner planets are rocky and dense.

7. The Inner Planets • Mercury which is closest to the sun is about the size of earth’s moon. • Like the moon, Mercury has no atmosphere and a surface covered with craters and dust. • The side of mercury that faces the sun is hot – (810 F). The side of the planet that does not face the sun is very cold – 290F • Venus is the brightest object in the night sky, after the moon. • This planet is about the same size as Earth. Venus can become very hot, – (860 F). It is even hotter than Mercury because its atmosphere keeps heat from escaping. Mercury Venus

8. The Inner Planets • Earth’s atmosphere and its liquid water make it the only planet know to support life. Earth’s atmosphere keeps the planet at temperatures at which living things can survive. • Mars is called the red planet because of its reddish soil. Its atmosphere is mostly carbon dioxide. It’s river valleys are evidence that Mars once had liquid water. • Mars has the largest volcanoes in the Solar System. • It also has dust storms that can last for months. Earth Mars

9. The Outer Planets • Beyond the inner planets are the five outer planets. In order from the sun, they are Jupiter, Saturn, Uranus, Neptune, and Pluto.

10. The Outer Planets • Jupiter is the largest planet in the solar system. It has a ring, dozens of moons. • There is a huge storm on Jupiter that has lasted for 400 years. This storm has been named the Great Red Spot. • Saturn is best known for its rings, which is made of ice, dust, boulders, and frozen gases. • Like Jupiter, Saturn has dozens of moons. • Jupiter and Saturn are the only planets that can be seen from a telescope. Jupiter Saturn

11. The Outer Planets • Uranus also has many moons and rings. This planet rotates on an axis that is tilted much more than those of the other planets. • It appears that Uranus is rolling around its orbit rather than spinning. • Neptune has several rings and moons and the strongest winds in the solar system. • Both Neptune and Uranus are similar in size. Uranus Neptune

12. The Outer Planets • Pluto is small and rocky, unlike the other outer planets. It also has an unusual orbit. Sometimes part of Pluto's’ orbit passes inside the orbit of Neptune, making Neptune the farthest planet from the sun at times. • Pluto’s moon, Charon, is nearly as big and the planet itself. • Scientist claim that Pluto is not a planet because it is unlike the other planets in the solar system. • Other scientists claim that Pluto and its moon form a double planet, because they are the same size, and they are made of very similar materials.

13. The Outer Planets • Scientists have recently gathered data that shows that there might be a 10th planet in the solar system. • The discover, Sedna, is the most distant object from the sun. Approx. 10 billion miles away. • Sedna is three-quarters the size of Pluto, so some scientist argue that it is big enough to be a planet.

14. Asteroids and Comets • Between Mars and Jupiter is the asteroid belt. This is a ring shaped region where thousands of small, rocky bodies called asteroids are located. Scientists hypothesize that asteroids in the asteroid belt are pieces of what may have been a planet orbiting between Mars and Jupiter.

15. Asteroids and Comets • Other pieces of rock that travel through space are called meteors. When a meteors hits Earth’s Atmosphere, it usually burns up. This causes the bright strike of light, or “Shooting Star” that you see in the sky. • A comet may pass close to the sun and then seen out past the orbit of Pluto, to the edge of the solar system. • Each time a comet approaches the sun, it changes. The center, or core, of the comet begins to melt. This forms a cloud of gas that is pushed into a long tail by energy from the sun. Meteors Comets

16. Asteroids and Comets • Many comets have been named for the people who discovered them. One is Halley’s Comet, which was last seen from Earth in 1986. It will appear again in 2061-2062 as part of its 76-year orbit around the sun.