Lecture 11

Moon Phases and Eclipses

Full Moon near Saturn

The Moon will be full on Sunday, 4/17/11 so

on Saturday and Sunday night it will

be near Saturn, which reached opposition

last week and, like the full Moon, is on the opposite side of the

sky as the Sun.

In each phase of the Moon, how much of the Moon is lit up by the Sun? Half the Moon is always

lit by the Sun

Except . . .

When the Earth’s shadow hits the Moon we have a …….

Lunar Eclipse

Eclipses occur ONLY when the Moon crosses the plane of Earth’s orbit around the Sun AND

ONLY during the NEW or FULL phases

Lunar Eclipse

• When Earth blocks most of the sunlight from illuminating the Moons surface for several hours when in the full moon phase

When the Moon’s shadow hits the Earth, we have a ….

Solar Eclipse

Solar Eclipse

Annular Eclipse

Partial Eclipse

Total Eclipse

Eclipses occur ONLY when the Moon crosses the plane of Earth’s orbit around the Sun AND

ONLY during the NEW or FULL phases

Which positions cause which eclipses

• When the ______ is in the _____ phase and is directly in line with the _____ and the ____ , you get a ______ eclipse?

• When the ______ is in the _____ phase and is directly in line with the _____ and the ____ , you get a ______ eclipse?

Moon fullEarth Sun

MoonEarth Sun

new

lunar

solar

When the full Moon is rising in the East, what is the Sun always doing?

The Sun is always setting in the West.

Therefore the Sun and Moon are exactly ________ degrees apart…try a human animation if you are having difficulty visualizing this.

The only exception is …

180

…if there is a lunar eclipse, with the Moon crossing the line of nodes.

How are the motions and positions of Earth and the Sun connected to what

happens on Earth?• Earth’s rotation on its axis determines the

length of the day.

• Earth’s orbit around the Sun determines the length of the year.

• The tilt of Earth’s rotational axis with respect to the plane of Earth’s orbit causes the seasons.

The changing phases of the Moon originally inspired the concept of the month

Watch Movie at:http://antwrp.gsfc.nasa.gov/apod/image/9911/lunation_ajc.gif

Moon Phase Names• New Moon• Waxing Crescent• First Quarter• Waxing Gibbous• Full Moon • Waning Gibbous• Third Quarter• Waning Crescent

The Causes of Moon Phases

• Think to yourself about the answer to this question:

What causes the phases of the Moon?

Take out a piece of paper and quickly write out a brief answer.

How long does it take to complete the full cycle of Moon Phases?

A. About a dayB. About a weekC. About a monthD. About a yearE. None of the above

Check your answer with your partner!

Solar Period vs. Sidereal Period of the Moon

Synodic (Solar) vs. Sidereal Periodof

the Moon

Synodic Period is 29.53 days, Moon rotates to the orange line, more than 360 degrees; back to the same phase (new moon) as leftmost image.

Sidereal Period is 27.32 days, Moon rotates to the purple line (which should be parallel to the leftmost red dotted line), 360 degrees; not back to New Moon - same phase as leftmost image

Right now our Moon is just…

What phase is our Moon in right now?

Just a day past First Quarter

Discuss light fills in from the right-ish side.

http://www.clarkplanetarium.org/pages/nightSky

http://meteorshowersonline.com/lyrids.html

http://yasirlioneljordan.blogspot.com/2011/04/moon-phases-2011-february.html

Lunar Calendar

Let’s Watch some Moon Phase Animations!

Pay attention to where the Moon, Sun and Earth are located and how the Moon appears from Earth at each of these positions.

Look at how much of the Moon is illuminated when at each position.

Look at which side of the Moon is illuminated when at each position.

Animation

ZOOM IN

Prepare for Human Animation! Get volunteers! Look at tidal locking.

Discuss plane of Moon’s orbit and angle.

http://www.sumanasinc.com/webcontent/animations/content/moonphase.html

What is a monthly cycle

& what is a daily cycle?

Label the daily times and how

the Moon phases are

broken up over time. Name the phases of the Moon that are shown.

Discuss rising and setting.

Although the Moon is always

½ lit by the Sun, we see

different amounts of the lit portion from

Earth depending on

where the Moon is

located in its month-long

orbit.

1) How many phases shown in the picture will the Moon go through in one day?

2) How long does it take the Moon to complete one orbit? How many of the phases will the Moon have gone through in this time?

3) How long does it take the Earth to complete one rotation? How far will the Moon have moved?

4) How much of the Moons total surface is illuminated when it is in the New Phase? Full Phase?

5) How much of the illuminated surface of the Moon is visible from Earth when it is in the First Quarter Phase, Full Phase?

6) What time is it when the Waxing Gibbous Phase is highest in the sky, Rising? Setting? What phase will it be in one week later….see next slide for answer. SKIP RED PORTION.

A Moon Phase is highest in the sky at 9 pm today. What phase will the Moon have in three weeks after today?

Lecture Tutorial: Cause Moon Phases

• Work with a partner!• Read the instructions and questions carefully.• Discuss the concepts and your answers with one

another. Take time to understand it now!!!!• 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.

A few more resources you might enjoy!

Animations:

more complex demo. http://jove.geol.niu.edu/faculty/stoddard/JAVA/moonphase.html

Useful information and tables as covered in class:http://home.hiwaay.net/~krcool/Astro/moon/moonphase/Gives information on the different moon phases and the times of day when they are visible.