Eclipses

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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 solar eclipse, you need to be on a particular part of the Earth

Solar and Lunar Eclipses

What is an eclipse?

• An eclipse occurs any time something passes in front of the Sun, blocking its light. This can be the Earth or the Moon.

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Why is the Moon red during an eclipse?

• The Earth’s atmosphere filters some sunlight and allows it to reach the Moon’s surface

• The blue light is removed—scattered 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 Earth’s atmosphere

6Images from Fred Espenak

http://www.mreclipse.com/LEphoto/LEgallery1/LEgallery1.html

Is there more than 1 kind of eclipse?

• Yes!! There are lunar and solar eclipses.

• Lunar Eclipse- When the Earth casts a shadow on the moon, causing the moon to go dark.Earth comes between the Sun and the Moon and casts a shadow on the Moon (Full Moon)

• Solar Eclipse- When the Moon casts a shadow on the Earth, causing the sun to go dark.The Moon comes between the Sun and Earth and casts a shadow on part of Earth (New Moon)

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Lunar Eclipse

• 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)

Lunar Eclipses• The Earth moves between the Sun and the

Moon, blocking th Sun’s light, and causing the moon to glow red.

• Umbra – The dark inner portion of the shadow cone.

• Penumbral – the lighter outer portion of the shadow.

Types of Lunar Eclipses• Total Lunar Eclipse – when the Moon passes

completely into the Umbra, or total shadow of the Earth.

• Partial Lunar Eclipse – Occur when the Moon does not fully move into the Umbra.

• Penumbral Lunar Eclipse – When the moon passes only through the penumbra, or partial shadow. They are barely visible.

Total Lunar Eclipse – when the Moon passes completely into the Umbra, or total shadow of the Earth.

Partial Lunar Eclipse – Occur when the Moon does not fully move into the Umbra

Penumbral Lunar Eclipse – When the moon passes only through the

penumbra, or partial shadow. They are barely visible.

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Solar Eclipses• When the Moon’s shadow covers part of the Earth

• Only happens at New Moon

• Three types: Annular, Partial, and Total

Types of Solar Eclipses

• Total Solar Eclipse – can only occur if you are at the exact spot within the moon’s umbra (which isn’t very big).

• Partial Solar Eclipse – Visible is you are in the penumbra of the shadow. Only some of the moon will be shadowed.

• Annular Eclipse – occurs when the moon is farthest from the Earth in its orbit. This makes the moon look smaller, so during the eclipse you see an outer ring of light from the Sun.

Total Solar Eclipse – can only occur if you are at the exact spot within the moon’s umbra (which isn’t very big).

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Total Solar Eclipse• Observers in the “umbra” shadow see a total eclipse (); can see the corona• Those in “penumbra” see a partial eclipse—not 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_008.php

Partial Solar Eclipse – Visible if you are in the penumbra of the shadow. Only some of the moon will be shadowed.

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Annular Solar Eclipse• When the Moon is too far to completely cover the Sun—the umbra

doesn’t reach the Earth

• Sun appears as a donut around the Moon

Annular Eclipse – occurs when the moon is farthest from the Earth in its orbit. This makes the moon look smaller, so during the eclipse you see an outer ring of

light from the Sun.

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Photos of an Annular Eclipse

http://sunearthday.nasa.gov/2006/multimedia/gal_010.php; photos taken by Fred Espenak

How often do Eclipses Happen?

• That depends!! Lunar Eclipses happen more often than Solar Eclipses.

• Why? Well everyone who is experiencing nighttime during a lunar eclipse can see it.

• But you have to be at the exact spot on Earth to see a Solar Eclipse.

• The spot on Earth is so small, that the same place only sees a Solar Eclipse every 350 years!!

Why Don’t We See LunarEclipses More Often?

• Well, lunar eclipses don’t happen everyday because the Moon’s orbit is tilted. So, during most months, the Moon is above or below the Earth.

Lunar Eclipses happen when the Moon passes through

Earth’s shadow, whereas solar eclipses happen when

Earth passes through the Moon’s shadow.

SOLAR ECLIPSE