Lunar Phases and Eclipses animated GIF created by Antonio Cidadao Barbara Gage PSC 1210 Prince George’s Community College

Lunar Phases and Lunar Phases and EclipsesEclipses

animated GIF created by Antonio Cidadao

Barbara Gage PSC 1210 Prince George’s Community College

Lunar PhasesLunar Phases Because of the rotation of the Earth, the Because of the rotation of the Earth, the

Moon appears to rise and set in the same Moon appears to rise and set in the same manner as the Sun does (east to west).manner as the Sun does (east to west).

The Moon revolves around the Earth The Moon revolves around the Earth counter-clockwise (looking down from the counter-clockwise (looking down from the North Pole) while the Earth revolves around North Pole) while the Earth revolves around the Sun (also counter-clockwise from the Sun (also counter-clockwise from northern view).northern view).

The phase of the Moon that we see from The phase of the Moon that we see from Earth depends upon the alignment of the Earth depends upon the alignment of the Sun, Moon, and Earth at any given time as Sun, Moon, and Earth at any given time as they revolve.they revolve.

http://astro.unl.edu/naap/lps/animations/lps.html

Here is a web site that allows you to see ananimation of the positions of the Earth, Moon,and Sun. It will illustrate the lunar phasesas the Moon revolves around the Earth.

Aspects of Lunar PhasesAspects of Lunar Phases

One half of the Moon’s surface is One half of the Moon’s surface is always illuminated by the Sun.always illuminated by the Sun.

When the Moon is in any position in When the Moon is in any position in the hemisphere between the Sun and the hemisphere between the Sun and the Earth, less than 50% of the lunar the Earth, less than 50% of the lunar surface we see will be illuminated. surface we see will be illuminated. During this time we see the During this time we see the newnew and and crescent phasescrescent phases..


Diagram modified from http://astro.unl.edu/naap/lps/lunarPage2.html

Hemisphere betweenSun and Earth

Hemisphere betweenEarth and outer space



When the Moon is in any position in When the Moon is in any position in the hemisphere between the Earth the hemisphere between the Earth and outer space, more than 50% of and outer space, more than 50% of the lunar surface we see will be the lunar surface we see will be illuminated. During this time we see illuminated. During this time we see the the fullfull and and gibbous phasesgibbous phases..







When the Moon is at the cross-over When the Moon is at the cross-over point between these two point between these two hemispheres, the phase we see is hemispheres, the phase we see is the the quarter phasequarter phase..





Aspects of Lunar PhasesAspects of Lunar Phases The illumination and The illumination and

darkening sections seem darkening sections seem to “move” from right to to “move” from right to left across the Moon’s left across the Moon’s surface over the course surface over the course of a lunar cycle. of a lunar cycle.

When the illumination is When the illumination is increasing, we say the increasing, we say the phase is phase is waxingwaxing. When . When the illumination the illumination decreases it is called decreases it is called waningwaning..

Lunar PhasesLunar PhasesWaxing crescent

Waxing crescent – 1st quarter – waxing gibbous

Waxing gibbous

Full – waning gibbous

Waning gibbous – waning crescent

Waning crescent

Photo from: http://aa.usno.navy.mil/graphics/Moon_phases.jpg

EclipsesEclipses

When the Sun or Moon is blocked to When the Sun or Moon is blocked to an observer on Earth over a short an observer on Earth over a short period of time (minutes to hours) an period of time (minutes to hours) an eclipseeclipse has occurred. has occurred.

If the Sun is blocked it is a If the Sun is blocked it is a solar solar eclipseeclipse..

If the Moon is blocked it is If the Moon is blocked it is lunar lunar eclipseeclipse..

Lunar EclipseLunar EclipseWhen the Moon is in the full moon position, the light from the Sun may be blocked by the Earth which casts a shadow. As the Moon travels into the shadow it is gradually covered. Ancients thought the Moon was being eaten.

http://www.hermit.org/Eclipse/why_lucnar.html

View from above the Northern Poles

Lunar EclipseLunar Eclipse

Shouldn’t there be a lunar Shouldn’t there be a lunar eclipse every time we eclipse every time we have a full moon?have a full moon?


The Earth revolves around the Sun on a plane called the plane of the ecliptic.

The Moon orbits Earth on a plane but that plane is tilted 5o

with respect to the plane of the ecliptic. This means that when the moon is in the full position it may be above or below the shadow of the Earth and no eclipse will occur.

Diagrams from http://www.ap.stmarys.ca/demos/content/astronomy/lunar_eclipse/lunar_eclipse.html


1 2

3

4

In positions 1 and 2 the Moon’s orbital tilt places the Moon-Earth-Sun in alignment so a lunar eclipse can occur. At positions 2 and 3, even though the lunar phase is full, the Earth’s shadow misses the Moon so no eclipse occurs.

Lunar Eclipse SequenceLunar Eclipse Sequence

Passing into the shadow

Totality

Coming out of the shadow

Solar EclipseSolar Eclipse

http://www.hermit.org/eclipse/why_solar.html

When the Moon passes directly between the Earth and the Sun, the Moon casts a shadow on the Earth. Where the shadow falls, observers will see an eclipse of the Sun, a solar eclipse. As with a lunar eclipse, the shadow of the Moon may fall above or below Earth and no eclipse occurs. If the entire Sun is covered we see a total eclipse; of only part if the surface is blocked we see a partial eclipse.

Solar EclipseSolar Eclipse This is a photo taken from the former Soviet space station MIR. It shows the shadow of the Moon falling on the Earth in 1999. Anyone under the shadow saw a solar eclipse.


http://www.hermit.org/eclipse/why_solar.html

If the Moon’s shadow falls short, an observer on Earth will see only some of the Sun’s surface blocked. This configuration results in an annular eclipse.


http://sunearth.gsfc.nasa.gov/eclipse/SEmono/TSE2006/TSE2006.html

The royal blue line through Africa and Asia shows the path for the March 29, 2006 solar eclipse. Observers on this path saw some stage of the eclipse.

http://sunearth.gsfc.nasa.gov/eclipse/solar.html

The link below will take you to the NASA pagethat lists all the solar eclipses for the next few years.

There will not be another annular eclipse untilFebruary 7, 2008. The next total solar eclipse will occur on August 1, 2008. Most of the visible area for these eclipses is ocean.

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Lunar Phases and Eclipses animated GIF created by Antonio Cidadao Barbara Gage PSC 1210 Prince George’s Community College