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Astronomy 1010
Planetary Astronomy
Fall_2015
Day-10
Course Announcements
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SW chapter -2 due: Mon. 9/21; 2pm
How is the lunar observing going?
1st Quarter night – Mon. 9/21 -7:30pm – on campus
Exam 1: Mon. Sept. 21
This Week: APSU-OUR: Research & Creative Activity
Week. Events in the library 2:30-3:30 every day.
Stuff in Chapter 2
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Coordinates
Position
Daily Motion (spin of Earth on its axis)
Visibility of the sky
Year Motion (Earth orbits the Sun)
Seasons (tilt of the Earth’s axis)
Precession of the equinoxes
Motion and phases of the Moon
Eclipses
Precession
 Currently, the north
celestial pole is near
the bright star
Polaris.
 Earth’s axis wobbles
with a period of
26,000 years.
 Location of the poles
slowly shifts.
 Earth wobbles like a top, slowly.
 Since the axis shifts, the equator shifts.
 Positions of the equinoxes precess as well.
Stuff in Chapter 2
•
•
•
•
•
•
•
•
•
Coordinates
Position
Daily Motion (spin of Earth on its axis)
Visibility of the sky
Year Motion (Earth orbits the Sun)
Seasons (tilt of the Earth’s axis)
Precession of the equinoxes
Motion and phases of the Moon
Eclipses
The Moon’s Motions
 Because the orbit
is elliptical and
not circular, the
rotation speed
doesn’t always
match the orbital
speed.
The Month?
Full Moon to Full Moon takes 29.53 days
The Cycle of Lunar Phases
The moon does rotate.
The moon takes the same amount of
time to complete one rotation as it does
to complete one orbit
The orbital period is not the
same as the cycle of phases
The Orbital Period is the Sidereal Month:
27.32 days
Cycle of phases:
The synodic month
29.53 days
Lecture – Tutorial
Cause of Moon Phases: pg 81
 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 one of us for help.
i_Clicker Question
 ClassAction: Questions:
 Lunar Cycles: Phase Evolution; option 1
Lecture – Tutorial
Predicting Moon Phases: pg 85
 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 one of us for help.