1. Introduction to the Solar System The solar system is made up of the sun, orbiting planets, their moons, and other objects traveling around the sun. The sun is the nearest star to the Earth.

2. Essential Questions What are the objects in our solar system? How can technology be used to observe distant objects in the sky? How does the optical telescope differ from the radio telescope?

3. What is a planet? A planet is a large body of rock or gas in space that moves around a star. A planet DOES NOT produce light of its own. That is why planets almost never twinkle as stars twinkle. You can see planets in the night sky because of the sun’s light reflecting or bouncing off of them.

4. Moon You can also see Earth’s moon in the night sky. A MOON is a small, rounded body in orbit around a planet. A moon does NOT produce its own light. It reflects light from the sun. Most planets have at least one moon.

5. Moon

6. Earth’s Year The farther a planet is from the sun, the longer it takes to orbit. The time it takes to complete one trip around the sun is called a YEAR. Earth’s year is about 365 days long. Mercury makes a complete orbit in just 88 days. Neptune takes about 165 Earth years to complete its orbit around the sun.

7. Sun, Moon, and Sky For thousands of years, people have been observing the sun, the moon, and other objects in the sky. Scientists did not learn how these objects move until a few hundred years ago. Why do you think they took so long?

8. Telescopes A telescope is a tool that makes distant objects appear larger, brighter, and sharper. Telescopes help scientists study stars, the moon, and the planets. Scientists have used telescopes to discover that stars have regular patterns, and planets move among the stars.

9. Never Look at the Sun NEVER look straight at the sun, especially with a telescope. Doing so can damage your eyes. It is SAFE to look at other stars that are more distant than the sun.

10. Optical Telescope

11. Hubble Telescope

12. Hubble Space Telescope It is different from other telescopes because it is in space. It moves around the Earth every 97 minutes. It was launched into space in 1990. It is the size of a school bus. It takes photographs of space from beyond Earth’s atmosphere.

13. Radio Telescope This type of telescope collects radio waves instead of light. Computers use the radio waves to make pictures of space. As more powerful telescopes are invented, scientists learn more about objects in space.

14. Radio Telescope

15. Essential Questions What are the objects in our solar system? How can technology be used to observe distant objects in the sky? How does the optical telescope differ from the radio telescope?