Imagining a spinning Celestial
Sphere surrounding Earth aids in
thinking about the position and
motion of the sky.
Did you get the Key Ideas from the Position
Lecture Tutorial?
Celestial Sphere Rotation
In what direction
is the observer
facing?
Star B
2
Star A
1
2
Celestial Sphere
Celestial Sphere
3
1
4
A) toward the South
B) toward the North
C) toward the East
D) toward the West
3
4
Celestial Sphere Rotation
Figure 2
Horizon
Where would the
observer look to
see the star
indicated by the
arrow?
Celestial Sphere Rotation
Star B
2
Star A
1
2
Celestial Sphere
Celestial Sphere
3
1
4
3
A) Low in the Northeast
B) Low in the Southeast
4
C) Low in the Northwest
Celestial Sphere Rotation
D) Low in the Southwest
Figure 2
Horizon
Imagine that from your current location you
observe a star rising directly in the east.
When this star reaches its highest position
above the horizon, where will it be?
A.
B.
C.
D.
high in the northern sky
high in the southern sky
high in the western sky
directly overhead
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
Earth’s
rotation
causes the
Sun, Planets,
Moon and
stars to
appear to
move when
viewed from
Earth
Looking North: Circumpolar
Stars
– Circumpolar stars seem to move counter-clockwise
around the stationary North Star.
– These constellations and stars are visible any night of the
year in the NORTHERN sky because they never rise or
set!
– Examples: Ursa Major, Ursa Minor, Draco, Cepheus, and
Cassiopeia
What happens over time in the
Northern Sky?
How long did it take
to get this picture?
What direction is
the camera
pointed?
Nightly Motion of the Stars
• Imagine looking toward the East as a star
rises above your horizon - what does it do
after that?
Nightly Motion of the Stars
Celestial Sphere Rotation
Star B
2
Star A
1
2
Celestial Sphere
Celestial Sphere
3
1
4
3
4
Celestial Sphere Rotation
Figure 2
Horizon
Nightly Motion of the Stars

For stars (the Moon and planets) that
appear in the southern sky: Stars first
rise near the eastern horizon, move
upward and toward the south, and then
move down and set near the western
horizon.
What
direction is
the camera
facing in
this picture
What
direction is
the
observer
facing in
this
picture?
What direction
is the observer
facing in this
picture?
Tutorial: Motion – p. 3
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Work with a partner!
Read the instructions and questions carefully.
Discuss the concepts and your answers with one
another.
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.
Post Tutorial Question

You are looking toward the north and see the
Big Dipper to the right of Polaris. Fifteen
minutes later, the Big Dipper will appear to have
moved in roughly what direction?
A) east (to your right)
B) west (to your left)
C) up (away from the horizon)
D) down (closer to the horizon)
Post Tutorial Question

How much time is there between when a star
rises and when it sets?

A) less than twelve hours

B) about twelve hours

C) more than twelve hours

D) It depends on the star.
GO CONFIDENTLY IN THE
DIRECTION OF YOUR DREAMS!!
LIVE THE LIFE YOU’VE IMAGINED