Eclipse !Eclipse !

Hey! You’re blocking my light!Hey! You’re blocking my light!

Eclipse TerminologyEclipse Terminology

Solar vs. lunarSolar vs. lunarTotal, partial, annularTotal, partial, annularUmbra, penumbra, eclipse (shadow) trackUmbra, penumbra, eclipse (shadow) trackCorona, diamond ring effectCorona, diamond ring effectAscending node, descending nodeAscending node, descending node

first type of eclipsefirst type of eclipse

Solar – the sun is eclipsed (blocked) by Solar – the sun is eclipsed (blocked) by the moon. The moon casts the shadow the moon. The moon casts the shadow onto the earth & therefore must be onto the earth & therefore must be between the sun & earth.between the sun & earth.

What phase does the moon have to be in What phase does the moon have to be in for this type of eclipse to occur?for this type of eclipse to occur?

NEW

22ndnd type of eclipse type of eclipse

Lunar – the moon is eclipsed (blocked) by Lunar – the moon is eclipsed (blocked) by the earth. The earth casts its shadow onto the earth. The earth casts its shadow onto the moon, and therefore must be between the moon, and therefore must be between the sun & moon.the sun & moon.

What phase does the moon have to be in What phase does the moon have to be in for this type of eclipse to occur?for this type of eclipse to occur?

Full

If the sun, earth, and moon just need tobe in alignment for an eclipse to occur…

then why don’t we have 1 solar and 1 lunareclipse every month?

The 3 bodies need to be alignednot only horizontally, butvertically too…and the moon’sorbit is tilted.

The 2 points where the moon’s orbitintersects the ecliptic are called theascending & descending nodes.

Solar Eclipses…3 typesSolar Eclipses…3 typesTotal – the entire face of the sun is Total – the entire face of the sun is

blocked by the moon.blocked by the moon.Partial – alignment isn’t perfect, and Partial – alignment isn’t perfect, and

only some of the sun’s disk is only some of the sun’s disk is blocked.blocked.

Annular – the moon is too far away to Annular – the moon is too far away to completely cover the face of the sun. completely cover the face of the sun. A ring of sun surrounds the moon.A ring of sun surrounds the moon.

A Total Solar EclipseA Total Solar Eclipse

An Annular Solar EclipseAn Annular Solar Eclipse

April, 1995

Partial Solar EclipsePartial Solar EclipseThe moon is slightly above or below the ecliptic.

A total solar eclipse begins Feb-26-1979.

Themoon’sshadow

Just as the sundisappears…it forms the“diamond ring”effect.

When the entire sunis eclipsed, some ofthe prominences(storms on the sun’ssurface) maybecome visible.

The outer layer of the sun’s atmosphere, the corona, becomes visible.

What does a solar eclipse look like What does a solar eclipse look like from space?from space?

1999,fromMir.

As the moon orbits around the earthin a counter-clockwise direction,the moon’s shadow slides over theearth from west to east, at about1000 miles per hour!

The path of the shadow is calledThe “eclipse track.”

http://www.fest.org.za/eclipse_jun2001.html

http://www.fest.org.za/eclipse_dec2002.html

Switch Gears – Lunar EclipsesSwitch Gears – Lunar Eclipses

Lunar eclipses are less spectacular Lunar eclipses are less spectacular than solar eclipses, but occur much than solar eclipses, but occur much more frequently. Why?more frequently. Why?

The earth’s shadow is 4 times thediameter, and 16 times the areaof the moon’s shadow.

Lunareclipsesare eitherpartial ortotal, butneverannular.

Lunar eclipsesLunar eclipsesWhen a total lunar eclipse occurs, the When a total lunar eclipse occurs, the

moon turns a pumpkin orange to a moon turns a pumpkin orange to a deep blood red.deep blood red.

This is because the earth’s This is because the earth’s atmosphere refracts some of the atmosphere refracts some of the sunlight around the earth, and sunlight around the earth, and dustdust in in our atmosphere scatters the blue & our atmosphere scatters the blue & green wavelengths, allowing the red green wavelengths, allowing the red to continue on to the moon.to continue on to the moon.

Direction of movement of the moonthrough the earth’s shadow.

What can eclipses tell us about our What can eclipses tell us about our solar system?solar system?

Ancient people knew that the moon Ancient people knew that the moon was much closer to the earth than the was much closer to the earth than the sun was. How did they know this?sun was. How did they know this?

Ancient people deduced that the sun Ancient people deduced that the sun was much larger than the moon, even was much larger than the moon, even though both appear the same size in though both appear the same size in the sky (angular diameter of ½the sky (angular diameter of ½oo.).)

Diameter of sunDiameter of sun = = distance to sundistance to sunDiameter of moon distance to moonDiameter of moon distance to moon

XX = = 93,000,000 miles93,000,000 miles 2000 miles 2000 miles 240,000 miles240,000 miles

X = about 800,000 milesX = about 800,000 miles

Predicting EclipsesPredicting Eclipses

Solar Eclipses can only occur when Solar Eclipses can only occur when the moon is in new phase the moon is in new phase andand on the on the ecliptic (at a node).ecliptic (at a node).

Generally, 2 solar eclipses occur Generally, 2 solar eclipses occur every year (although the eclipse track every year (although the eclipse track may cross an un-inhabited part of the may cross an un-inhabited part of the earth.)earth.)

Predicting EclipsesPredicting Eclipses

Lunar eclipses can only occur when Lunar eclipses can only occur when the moon is full phase and on the the moon is full phase and on the ecliptic (at a node).ecliptic (at a node).

Lunar eclipses occur 2 weeks before Lunar eclipses occur 2 weeks before and/or 2 weeks after a solar eclipse. and/or 2 weeks after a solar eclipse.

Slide CreditsSlide Credits

Wadsworth Publishing Co.Wadsworth Publishing Co.www.MrEclipse.comwww.MrEclipse.comwww.chara.gsu.eduwww.chara.gsu.eduNASANASAwww.fest.org.zawww.fest.org.zawww.vcharkarn.comwww.vcharkarn.com

Some potential extra creditSome potential extra credit

Use the Distant Suns 4 program to plot the Use the Distant Suns 4 program to plot the phase of the moon (as % illumination) on phase of the moon (as % illumination) on graph paper. You will get a sinusoidal graph paper. You will get a sinusoidal (sine wave) type curve.(sine wave) type curve.

Use the same program to determine the Use the same program to determine the distance of the moon from the ecliptic. distance of the moon from the ecliptic. Plot this distance above/below the ecliptic Plot this distance above/below the ecliptic on the on the same graphsame graph. This will also be a . This will also be a sine wave curve.sine wave curve.

Some potential extra creditSome potential extra creditWhere the 2 graphs intersect at the points Where the 2 graphs intersect at the points

of new moon (0% illumination), a solar of new moon (0% illumination), a solar eclipse could occur.eclipse could occur.

Where the 2 graphs intersect at the points Where the 2 graphs intersect at the points of full moon (100% illumination), a lunar of full moon (100% illumination), a lunar eclipse could occur.eclipse could occur.

Use this graphing method to predict the Use this graphing method to predict the next 3 eclipses (of any type), for 20 points next 3 eclipses (of any type), for 20 points of extra credit.of extra credit.