ASTR-1010ASTR-1010Planetary AstronomyPlanetary Astronomy

Day - 10

HOMEWORKHOMEWORK

Homework Chapter 2: Due Today

Motions of the Sun – Due Today

Exam -1 – Next time– chapters 1 & 2 only.

- Look at Smartworks, Lecture-Tutorials, ClassAction questions, and remember the labs.

Eclipses!Eclipses!

There are two types of There are two types of eclipses: Solar and Lunareclipses: Solar and Lunar

Why don’t we have an eclipse Why don’t we have an eclipse every month?every month?

The moon doesn’t orbit on the Earth’s equator or on the ecliptic

Eclipses only occur when the Eclipses only occur when the Earth, Sun and Moon all line Earth, Sun and Moon all line

upup

Lunar Eclipse: the Earth passes Lunar Eclipse: the Earth passes directly between the Sun and directly between the Sun and

MoonMoon

The Total Lunar EclipseThe Total Lunar Eclipse

Next one is December 21, 2010 in the early morning

A Solar Eclipse requires A Solar Eclipse requires much more precise much more precise

alignmentalignment

The Moon’s shadow is not The Moon’s shadow is not large enough to cover the large enough to cover the

EarthEarth

Solar Eclipses take hours to Solar Eclipses take hours to develop but last only develop but last only

minutesminutes

During a total eclipse the During a total eclipse the Sun’s corona is visibleSun’s corona is visible

Partial eclipses are more Partial eclipses are more common than total common than total

eclipseseclipses

Annular Annular Eclipses Eclipses

occur occur when the when the Moon is at Moon is at

or near or near apogeeapogee

Predicting EclipsesPredicting EclipsesThe Saros Cycle…18 years 11.3 days

Lecture – TutorialLecture – Tutorial

Path of the Sun: pg 87Path of the Sun: pg 87• 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.

Lecture – TutorialLecture – Tutorial

Seasons: pg 91Seasons: pg 91

Homework!You won’t have to turn it in on

Wednesday but there will be questions on the exam out of it