Astronomy 1010Fall_2014

Day-9Planetary Astronomy

Course Announcements• Smartworks Chapter 2: Fri. 9/19

• Read Chapter 2, 3

• Dark Night Observing – • Tues. 9/16 & Wed. 9/24 – 7:30pm at the

Observatory

• Exam-1 – Friday Sept. 19

Lecture – TutorialPath 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.

Lecture – TutorialSeasons: pg. 93

Work with a partner!Yada Yada Yada …This one is homework

Also, look at the ones on: pg 11 – Solar vs. Sidereal DayPg. 13 - Ecliptic

Stuff in Chapter 2Coordinates PositionDaily Motion (spin of Earth on its axis)Visibility of the skyYear Motion (Earth orbits the Sun)Seasons (tilt of the Earth’s axis)• Precession of the equinoxes• Motion and phases of the Moon• Eclipses

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.

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.

The Moon’s Motions

Because the orbit is elliptical and not circular, the rotation speed doesn’t always match the orbital speed.

Full Moon to Full Moon takes 29.53 days

The moon takes the same amount of time to complete one rotation as it does to complete one orbit

Cycle of phases:The synodic month 29.53 days

The Orbital Period is the Sidereal Month: 27.32 days

Lecture – TutorialCause 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.