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Astronomy 1010
Planetary Astronomy
Fall_2015
Day-9
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.
Useful Information for Next Lab
 Motions of the Sun
 ClassAction Web Site (Link from
apsu.edu/astronomy)
 Print the instructions BEFORE you come to
class!
That Picture Question
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37: <= 12hrs
14: 24 hrs
5: 10 hrs
4: 6 hrs
3: 14-16 hrs
2: “A night”
2: Answer had nothing to do with question
1: 5hr, 9.5hr, 8hr, 72 hrs,6 min, “Couple of days”, No
Answer
i_Clicker Question
 ClassAction: Questions:
 Basic Motion: Seasonal Analogy
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
Earth’s Axis
 Earth’s axis is not perpendicular to the ecliptic
plane.
 Instead, it is at an angle of 23.5 degrees.
 This is why there are seasons.
Earth’s Axis
 The angle of sunlight is closer to
perpendicular in summer.
 Energy is more concentrated.
 The southern hemisphere is opposite the
northern hemisphere.
Special Days of the Year
 Summer solstice: Sun
farthest north.
 Autumnal equinox: Sun
on the equator, moving
southward.
 Winter solstice: Sun
farthest south.
 Vernal equinox: Sun on
the equator, moving
northward.
Lecture – Tutorial
Path of the Sun: pg 89
 Work with a partner!
 Read the instructions and questions carefully.
 Discuss the concepts and your answers with each other.
 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:
 Coords & Motion: Sun Path 1
i_Clicker Question
 ClassAction: Questions:
 Coords & Motion: Sun Shadow
I Realize this is Like Trying to Drink
from a Fire Hose
Lecture – Tutorial
Seasons: pg. 93
 Work with a partner!
 Yada Yada Yada …
 This one is homework
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.