1. EARTH & SPACE Celestial Objects

2. Copyright © 2010 McGraw-Hill Ryerson Ltd. The universe includes everything that exists. This includes celestial objects such as stars and planets, plus all the matter and empty space surrounding them. THE UNIVERSE

3. Copyright © 2010 McGraw-Hill Ryerson Ltd. The solar system is a system of planets, including Earth, moons, and other objects, that orbit the Sun. The gravitational pull (a force of attraction between two masses) between the Sun and the planets keeps the planets revolving around the Sun. Our Solar System An orbit is the circular (or elliptical) path of one object around another object.

4. Copyright © 2010 McGraw-Hill Ryerson Ltd. A star is a massive ball of superheated gases that radiates heat and light. Characteristics used to describe stars include: size colour temperature and density Stars and Their Characteristics

5. Copyright © 2010 McGraw-Hill Ryerson Ltd. A galaxy is a collection of billions of stars, plus gas and dust, held together by gravity. There are billions of galaxies in the universe. Our solar system is located in a galaxy called the Milky Way. Galaxies: Collections of Stars

6. Copyright © 2010 McGraw-Hill Ryerson Ltd. Distances in space are so large that well-known units such as kilometres are almost meaningless. To measure the immense distances in space, astronomers have created a unit called the astronomical unit (AU). Distances in Space 1 AU is equal to the distance between Earth and the Sun, which is about 150,000,000 km.

7. Copyright © 2010 McGraw-Hill Ryerson Ltd. Distances involving galaxies are much larger than those involving solar systems. Instead of using AUs, scientists use a unit called a light-year, which is a measurement equal to the distance that light travels in one year. With light travelling at 300 000 km/s, one light-year is equal to about 9 500 000 000 000 km (9.5 x 10 12 km). Distances Involving Galaxies

8. Copyright © 2010 McGraw-Hill Ryerson Ltd. Galaxies come in many different sizes and shapes. Classifying Galaxies Bill Nye - Outer Space

9. Copyright © 2010 McGraw-Hill Ryerson Ltd. Key Concepts to be reviewed: We see stars that we organize into patterns. We see celestial objects of the universe. We see objects separated by immense distances. Topic 3.1 Review