At the scale of the Milky Way Galaxy, distances are described in terms of Light-years, which is the distance light travels in one year.

What do you think? Do the stars stay in the same position in the sky all day/night long? Do we see the same stars all year round every night?

What causes the stars to move? Do the stars actually move in the way they appear to be moving from Earth? Is the daily motion of the Sun different from the stars? What do you think?

Consider the dome of the sky over our heads…. mixing bowl

inverted mixing bowl …. Consider the dome of the sky over our heads….

Imagining a spinning Celestial Sphere surrounding Earth aids in thinking about the position and motion of the sky.

What would this look like from the ground?

Celestial Sphere Rotation North Star Star A Star B Earth’s Equator Figure 1 Celestial Sphere Celestial Sphere Rotation Celestial Sphere Star A Star B Figure 2 Horizon

Pre Tutorial Question You observe a star rising due east. When this star reaches its highest position above the horizon, where will it be? A) high in the northern sky B) high in the eastern sky C) high in the southern sky D) high in the western sky E) directly overhead

Tutorial: Position – p.1 Work with a partner. Read the instructions and questions carefully. Talk to each other and discuss your answers with each another, but BOTH write in your own book. Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group. If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask me for help.

Celestial Sphere Celestial Sphere Rotation Celestial Sphere Star A Star B Figure 2 Horizon Is the horizon shown a real physical horizon, or an imaginary plane that extends from the observer and Earth out to the stars? Can the observer shown see an object located below the horizon? Is there a star that is in an unobservable position? When a star travels from being below the observer’s horizon to being above the observer’s horizon, is that star rising or setting?

Post Tutorial Question Stars that never appear to set are called circumpolar. As you move from Earth’s equator toward the North Pole, the number of stars that are circumpolar A) increases. B) decreases. C) stays the same.

Post Tutorial Question Imagine you are standing at the North Pole. Of the stars that you can see, roughly how many of these stars are circumpolar? A) none B) less than half C) more than half D) all

Post Tutorial Question You are observing the sky from your southern hemisphere location in Australia. You see a star rising directly to the east. When this star reaches its highest position above the horizon, where will it be? A) high in the northern sky B) high in the eastern sky C) high in the southern sky D) high in the western sky E) directly overhead

In what direction would you face (look) to see Star A when it is highest in the sky? A) toward the north B) toward the south C) toward the east D) toward the west E) directly overhead

Which of the stars will set on the western horizon? A) both Star A and Star B B) only Star A C) neither Star A nor Star B D) only Star B

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