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Eclipses
• The Sun and Moon occasionally line up so that we have an eclipse.
• Revolution of the moon causes eclipses.
• An eclipse is defined as an astronomical event that occurs when one celestial object moves into the shadow of another, partially or fully obscuring it from view.
• Can only occur when the sun, the moon, and the Earth are lined up perfectly.
Two Types of Eclipses:
Solar Eclipse
Lunar Eclipse
Solar Eclipse• When the moon travels directly between the Sun and the
Earth and casts a shadow on part of Earth (blocks the Sun’s light from the Earth).
• Only possible at New Moon.• Because Earth rotates, it will take only a few minutes to move
out of the Moon's shadow.
Moon blocks out sun
Two Types of Solar Eclipses:
Total Solar EclipsePartial Solar Eclipse
Total Solar Eclipse• Observers in the “umbra” shadow see a total eclipse
where the moon completely blocks the Sun.• Umbra – darkest portion of the moon’s shadow.
Total Solar Eclipse
• Total eclipses are rare! Only once every 360 years from one location.• The entire Earth does not see a total eclipse. It depends on where the umbra and penumbra fall on the Earth.
Partial Solar Eclipse• Observers in the “penumbra” shadow see a partial
eclipse where the moon blocks part of the Sun.
• Penumbra – lighter shadow on Earth’s surface.
Lunar Eclipse
Lunar Eclipse
• Occurs during a Full Moon when Earth’s shadow falls on the moon.
• Begins when the moon moves into Earth’s penumbra.
• As the moon continues to move, it enters Earth’s umbra and you see a curved shadow on the moon’s surface.
• When the moon moves completely into Earth’s umbra, the moon becomes dark red because light from the sun is refracted by the Earth’s atmosphere onto the moon.
• About 2-3 per year; last up to 4 hours
Why not eclipses every month?
• The moon’s orbit around the earth is tilted slightly compared to the Earth’s orbit around the Sun.
• All three objects must be lined up vertically for an eclipse to occur.
Earth
Moon
MoonPlane of earth’s orbit
Plane of lunar orbit
