Eclipses and

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Eclipses and Lunar Phases
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Moon our closest natural neighbor

• The earths only natural satellite
• Orbit around the earth is an eclipse
• Average distance from the earth to the moon is
  384,403 kilometers (238,857 miles) 30 times the
  diameter of the earth
• Diameter of 3,474 km, ¼ of the earth
• Gravity 1/6 of the earth

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Moons orbit

• The orbit period around the earth 27.3 days
• The spin period is exactly the same!
• We always see the same side of the moon!
  ( precisely speaking 59 of the surface during
  the whole period of the moon revolution. Reason
  libration)
• The period of Lunar Phase 29.5 days
• Because of the earths revolution in the space
• The orbit plane of the moon is tilted by 5
  degree with respect to the earths orbit around
  the sun, unlike other planets

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Moons orbit

• The orbit plane of the moon is tilted by 5
  degree with respect to the earths orbit around
  the sun, unlike other planets

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Near Side
Far Side
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Preliminary Topics

• Before students can understand the reason for
  phases, they need to understand
• The Moon orbits the Earth.
• The Moon orbits at an angle with respect to the
  Earths orbit around the Sun.
• The Moon doesnt shine on its own it reflects
  sunlight.
• The scale of the Moon and Earths sizes and
  distance.

Ecliptic plane
Moons orbital plane
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The Moons Orbit around the earth
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APOGEE AND PERIGEE
APOGEE Moons furthest distance from the Earth.
Earth
Moon
Moon
PERIGEE Moons closest distance from the Earth.
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Phases--Causes

• The Sun shines on the Moon.
• When the sunlight reflects off the Moons far
  side, we call it a New Moon
• When the sunlight reflects off on the Moons near
  side, we call it a Full Moon
• Between New and Full, we see parts of the daytime
  side of the Moon.

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Moon Phases

• Why does the moon change phases?
• Lunar phases are the result of our eyes seeing
  the illuminated half of the Moon from different
  viewing angles.
• Due to the Moons orbital positions

SUN
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New (couple days)Waxing Crescent (several
days)1st QuarterWaxing Gibbous (several
days) FullWaning Gibbous (several days)3rd
QuarterWaning Crescent (several days)New
Phases Observing and Identifying
http//www.lpi.usra.edu/education/skytellers/moon_
phases/about.shtml
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starchild.gsfc.nasa.gov/docs/StarChild/questions/p
hases.html
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Eclipses

• The Sun and Moon occasionally line up so that we
  have an eclipse.
• These eclipses happen every year
• To see a Lunar Eclipse, you need only be on the
  night-time side of the Earth to see the Full Moon
  move into the Earths shadow.
• To see a Solar Eclipse, you need to be on a
  particular part of the Earth

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When the Earths shadow covers the Moon, we have
a lunar eclipse
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Three types of Lunar Eclipses

• Penumbral lunar eclipsethe Moon only passes
  through the penumbra of Earths shadow
• Partial lunar eclipsepart of the Moon passes
  through the umbra of Earths shadow
• Total lunar eclipsethe entire Moon passes
  through the umbra of Earths shadow
• Who on Earth will be able to see a lunar eclipse?

Anyone who can see the Moon (anyone who is on the
nighttime side of the Earth during the eclipse)
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Images from Fred Espenak http//www.mreclipse.com/
LEphoto/LEgallery1/LEgallery1.html
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Lunar Eclipses

• Moon the shadow of the earth on the moon

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Lunar Eclipse
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Why is the Moon red during an eclipse?

• The Earths atmosphere filters some sunlight and
  allows it to reach the Moons surface
• The blue light is removedscattered down to make
  a blue sky over those in daytime
• Remaining light is red or orange
• Some of this remaining light is bent or refracted
  so that a small fraction of it reaches the Moon
• Exact appearance depends on dust and clouds in
  the Earths atmosphere

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Upcoming Lunar Eclipses

• Mar 3, 2007, total lunar eclipse partial eclipse
  visible in USA
• Aug 28, 2007, total lunar eclipse partial
  eclipse visible in USA
• Feb 21, 2008, total lunar eclipse total in
  eastern USA and Texas
• Aug 16, 2008, partial lunar eclipse not visible
  in USA

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Solar Eclipses

• When the Moons shadow covers part of the Earth
• Only happens at New Moon
• Three types Annular, Partial, and Total

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A total eclipse B annular eclipse C partial
eclipse
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Solar Eclipses

• Sun the shadow of the moon on the earth

Total solar eclipse in 1999
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Total Solar Eclipse

• Observers in the umbra shadow see a total
  eclipse (safe to view the Sun) can see the
  corona
• Those in penumbra see a partial eclipsenot
  safe to look directly at Sun
• Only lasts a few minutes
• Path of Totality about 10,000 miles long, only
  100 miles wide

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Photo of a Total Eclipse
http//sunearthday.nasa.gov/2006/multimedia/gal_00
8.php
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Annular Solar Eclipse

• When the Moon is too far to completely cover the
  Sunthe umbra doesnt reach the Earth
• Sun appears as a donut around the Moon

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Photos of an Annular Eclipse
http//sunearthday.nasa.gov/2006/multimedia/gal_01
0.php photos taken by Fred Espenak
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QUESTION
Whats the moon phase when a solar eclipse occurs?
New Moon
Whats the moon phase when a lunar eclipse occurs?
Full Moon
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ANSWER!!
starchild.gsfc.nasa.gov/docs/StarChild/questions/p
hases.html

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Why arent there solar eclipses and lunar
eclipses on EVERY new moon and full moon?
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Upcoming Solar Eclipses

• Mar 19, 2007, partial solar eclipse visible in
  Asia and Alaska
• Sep 11, 2007, partial solar eclipse visible in
  South America and Antarctica
• Feb 7, 2008, annular solar eclipse visible in
  Antarctica and Australia
• Aug 1, 2008, total solar eclipse visible in
  Canada, Greenland, Europe and Asia
• Next Total Solar Eclipse in USAAugust 21, 2017

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Solar eclipses
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The Seasons
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The Seasons
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Lines of Latitude
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Summer and Winter

• June 21 Summer Solstice
• Suns rays directly above the Tropic of Cancer in
  N. Hemisphere.
• December 21 Winter Solstice
• Suns rays directly above the Tropic of Capricorn
  in the S. Hemisphere.

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BARYCENTER Common Center of Mass
Moon
R 0.75R
e
Where is the center-of-mass of the earthmoon?
Earth