Chapter 5 Lesson 2, "Distances to Stars"

Materials:

• Worksheet, "Distances to Stars"
• Optional Worksheet, Observing distant Objects.

Objective:

• Students will define a light-year.
• Students will explain how far away stars are.

Anticipatory Set:* The nearest star to our solar system visible from the northern hemisphere is Sirius. It is twice as big as the sun and 23 times brighter. So why can't we see it very well? How far away is it? How do we talk about distance when we are describing how far away stars are? Read these three statements while using these pictures:

Vacation: "Our family vacation spot is three days away"

Friends House: "My friends house is only 10 minutes away"

Hotel: "The hotel is 30 minutes from the airport"

Do these statements talk about time or distance? Review the pictures and describe what the statement means.

When we talk about the distances to stars we do the same thing. We use the term Light Year. What is a light year? (no its not this guy) Buzz Light year.

Teacher Input:* The signal we are sending back and forth travels near the speed of light. Have each sight wave their had in the air and see how long that takes to get back to them. The signal is going to Fairbanks and back in that time. This chart shows how far light will travel in seconds and minutes. This second chart shows how far light travels in one year.

This Map of surrounding stars shows their distance in light years.Is that easier to understand than this: Distance in miles. Think of it this way, light travels about 300,000 km per second if a spaceship could travel that fast it is over 1 billion km per hour. How long would it take to get to the sun at that speed? (8min 20 sec). But.. if we traveled at that speed to Sirrus it would still take us 9 years. You could hop in that spaceship traveling over a billion km/hr and you would still be in your mid 30's before you got back from Sirrus.

If a star that is 10 light years away blew up right now when would we know it happened?

Are stars that are next to one another close to each other? Look at the big dipper. What does the picture on Page 115 tell you about those stars.

How do we know how far a star is? There are a couple ways, here is the first: Use trigonometry.

The second is to recognize the type of star by the color and its components based on the color than compare its brightness to other stars. Show a picture of several stars. Pick two that look of different magnitude. Tell the students that astronomers determined that these are the same type of star burning at the same temperature and of the same brightness. Which is further away?

Guided Practice:* Assign each site a different question from Page 116. Have them answer those questions.

Independent Practice:* Students will complete the worksheet ,Distances to Stars. Students may complete the optional worksheet "Observing Distant Objects for extra credit"

Check for Understanding:* Does a light year represent an amount of time? Students will complete the quiz, Chapter 5 Lesson 2, "Distances to Stars"

Duration:

30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).

Alaska Content Standards Addressed in this lesson:

• SCI A-3 Students will understand models describing the composition, age, and size of our universe, galaxy, and solar system and understand that the universe is constantly moving and changing (Universe);
• SCI A-4 Students will understand observable natural events such as tides, weather, seasons, and moon phases in terms of the structure and motion of the earth (Earth);
• SCI A-15 Students will use science to understand and describe the local environment (Local Knowledge); and:

• SCI A-16 Students will understand basic concepts about the theory of relativity, which changed the view of the universe by uniting matter and energy and by linking time with space (Relativity).