THE MOONTHE MOON

The Moon

• The Moon is the 5th largest satellite in our Solar System.

• The Moon is about 4.6 billion years old.

The Moon

• The Moon is our nearest neighbor in space.

• On the Moon, you can always see the stars because the sky is always black.

• Apart from the Sun (apparent magnitude of -26), it is the brightest object in the sky with an apparent magnitude of -2.5 to -12 (full moon).

The Moon and the Earth

• The Moon is the largest natural satellite in relation to the size of its planet. The Moon is about ¼ the size of Earth.

• It is in synchronous rotation with Earth, always showing the same face. This means that from the Moon, the Earth would always look the same as well!

• The Moon is the only celestial body to be visited by humans.

• The Moon’s gravity is 1/6 of Earth’s gravity.• The Moon is moving away from Earth at a speed of

about 1½ inches (3.8 centimetres) per year. • Unlike Earth, the Moon has not changed much since its

“birth”.

Near Side of the Moon

• The part of the Moon we can see from Earth.

Far Side of the Moon

• The hemisphere of the Moon that the Earth does not see.

Can you see different parts of the Moon from different parts of Earth?

• The actual orientation you see the Moon in the sky or on the horizon depends on your geographic latitude on Earth.

• North pole: Moon appears low above the horizon with its North pole up.

• Mid Northern latitudes (North America, Europe, Asia): Moon rises in the East with its Northeastern limb up (Mare Crisium), it reaches it highest point in the South with its North on top, and sets in the West with its Northwestern limb (Mare Imbrium) on top.

Can you see different parts of the Moon from different parts of Earth?

• Equator: Moon rises in the East, its N-S axis appears horizontal and Mare Foecunditatis is on top. When it sets in the West the axis is still horizontal, but Oceanus Procellarum is the last area to dip below the horizon.

• Mid Southern latitudes (South America, South Pacific, Australia, South Africa): Moon rises in the East with its Southeastern limb up (Mare Nectaris), it reaches it highest point in the North with its South on top, and sets in the West with its Southwestern limb (Mare Humorum) on top.

• South pole: Moon appears low above the horizon with its South pole up.

Sun and Moon Comparison

• Similarities– Like the Sun, the Moon appears to move relative to

the background stars. – Both very bright (the two brightest objects in the sky)

• Differences – The Sun is large enough for nuclear fusion, unlike the

Moon and planets. – The Moon does not give off light of its own; it reflects

light from the Sun.– The Moon is made of metallic elements and appears

bright due to its coal-like reflectiveness.

Moon

• It takes 29.5 days for the Moon to rotate once on its axis.

• The Moon does not have seasons because it has only a 1.5° tilt.

http://www.enchantedlearning.com/subjects/astronomy/moon/

Moon Activity Questions

1) How many different Moon phases are there?

2) How many times did you see a spherical shape?

3) How many half-circles have you seen?

• Crescent shapes?

4) What affects how much of the moon we see?

Key Terms• Waxing: closer to a full moon (what we

see gets larger)• Waning: closer to a new moon (what we

see gets smaller)• Gibbous: convex or bulging outwards

appearance• Crescent: concave appearance

New MoonNew Moon

Waxing CrescentWaxing Crescent

First QuarterFirst Quarter

Waxing GibbousWaxing Gibbous

Full MoonFull Moon

Waning GibbousWaning Gibbous

Third QuarterThird Quarter

Waning CrescentWaning Crescent

Eclipses

• Eclipses only happen at new moon or full moon phases

• The Moon must also pass through the ecliptic

• There are 2 types of eclipses:– Lunar Eclipses– Solar Eclipses

Lunar Eclipses• The Sun and the Moon are

in exactly opposite directions, as seen from Earth

• Positions: Sun, Earth, Moon

• Earth’s shadow sweeps across the Moon, temporarily blocking the Sun’s light and darkening the Moon in a lunar eclipse

• Lunar eclipses only occur during FULL MOONS. This is when the Sun, Earth and Moon are lined up correctly.

• Lunar eclipses are safe to observe.• Typically 2 to 4 a year but it is possible

to have none at all in a year. They occur in clusters.

• Lunar eclipses are visible from all night-time Earth locations.

• Lunar eclipses do not occur during every full moon because the Moon's orbit around the Earth is not in the same plane as the Earth's orbit around the Sun (the ecliptic).

• The Moon's orbit is inclined about 5 degrees to the Earth's orbit. The Moon passes through the ecliptic only twice a month at a pair of points called the nodes. The rest of the time the Moon is either above or below the plane of the Earth's orbit.

Lunar Eclipses• Total Lunar Eclipse:

– The entire lunar surface is obscured – Total lunar eclipses last only as long as is needed for

the Moon to pass through Earth’s shadow—no more than about 100 minutes.

– During that time, the Moon often acquires an eerie, deep red coloration - the result of a small amount of sunlight reddened by Earth’s atmosphere (for the same reason that sunsets appear) and refracted (bent) onto the lunar surface, preventing the shadow from being completely black.

Total Lunar Eclipse Over Maui

Total Lunar Eclipse

• http://www.youtube.com/watch?v=IVkkCVh5t0E

Lunar Eclipses

• Partial Lunar Eclipse:– The alignment of the Sun, Earth, and Moon is

imperfect, so the shadow never completely covers the Moon.

– Very easy for amateurs

to see- All total Lunar eclipses

are followed by partial

Lunar eclipses

Partial Lunar Eclipse

• http://www.youtube.com/watch?v=C4b7KCFpJAI&feature=PlayList&p=0F9169A2DC5724F9&playnext_from=PL&index=5&playnext=1

Lunar Eclipses

Lunar Eclipse

• The umbra

(Latin for "shadow")

occurs when direct light from the source of illumination (Sun) is completely cut off.

• An observer in the umbra is said to be in the shadows experiencing total eclipse.

Lunar Eclipse• The penumbra is

the region in which only a portion of the light source is obscured. An observer in the penumbra experiences a partial

eclipse.

Eclipses Questions – Part 1

1) Explain the differences between a lunar eclipse and a new moon. 

2) Explain why lunar eclipses only happen during the full moon. 

3) Explain why lunar eclipses don’t happen every full moon.

4) Explain the difference between the penumbra and the umbra. 

Solar Eclipses

• The Sun and the Moon are in the same direction, as seen from Earth

• Positions: Sun, Moon, Earth• Day turns into night as the Moon blocks out

the Sun’s light (most of it)• Solar eclipses only occur during NEW

MOONS. • Solar eclipses are only visible from a small

part of the day-time Earth.

Solar Eclipses

Solar Eclipses

Antumbra Shadow• The antumbra is the region from which the

obstructing body appears entirely contained within the disc of the light source.

• If an observer in the antumbra moves closer to the light source, the apparent size of the obstructing body increases until it causes a full umbra.

Annular Solar Eclipse• An observer in this region experiences an

annular eclipse. • Roughly half of all solar eclipses are annular.

Types of Solar Eclipses

• 1) Total Solar Eclipse = umbra shadow

• 2) Partial Solar Eclipse = penumbra shadow

• 3) Annular Solar Eclipse = antumbra shadow

Types of Lunar Eclipse

• 1) Total Lunar Eclipse: umbra shadow

• 2) Partial Lunar Eclipse: penumbra shadow

Total Solar Eclipse

• Planets and stars are visible during the day!

• The Sun’s corona (outer atmosphere) is visible.

Partial Solar Eclipse

• Moon’s path is slightly "off center," and only a portion of the Sun’s face is covered.

Shadows…• The Moon’s shadow on Earth’s surface is about

7000 km wide—roughly twice the diameter of the Moon.

• Outside of that shadow, no eclipse is seen. • Within the central region of the shadow, called the

umbra, the eclipse is total. • Within the shadow but outside the umbra, in the

penumbra, the eclipse is partial, with less and less of the Sun obscured the farther one travels from the shadow’s center.

Why are solar eclipses rare?

• One reason that total solar eclipses are rare is that although the penumbra is some 7000 kilometers across, the umbra is always very small (< 270km).

• The shadow sweeps across Earth’s surface at over 1700 kilometers per hour, so the duration of a total eclipse at any given point can never exceed 7.5 minutes.

Key Term

• Totality: occurs at the point of maximum phase during a total eclipse, when the obscured object is completely covered.

• If you are not in the UMBRA of the shadow, you will see a partial eclipse and the eclipse will not reach totality.

Totality

• The Moon’s orbit around Earth is not exactly circular.

• Thus, the Moon may be far enough from Earth at the moment of an eclipse that its disk fails to cover the disk of the Sun completely, even though their centers coincide.

Totality

• In that case, there is no region of totality—the umbra never reaches Earth at all, and a thin ring of sunlight can still be seen surrounding the Moon. Such an occurrence is called an annular eclipse.

Path of Totality

• The track of the Moon's umbral shadow across Earth is called the Path of Totality.

• It is typically 10,000 miles long but only about 100 miles wide.

• The umbral shadow covers less than 1% of Earth's entire surface area.

• In order to see the Sun become completely eclipsed by the Moon, you must be somewhere inside the narrow path of totality or the umbral shadow.

Path of Totality

• The path of a total eclipse can cross any part of Earth.

• Even the North and South Poles get a total eclipse sooner or later.

• Just one total eclipse occurs each year or two.

• Since each total eclipse is only visible from a very narrow track, it is rare to see one from any single location.

Path of Totality

• You'd have to wait an average of 375 years to see two total eclipses from one place.

• Of course, the interval between seeing two eclipses from one particular place can be shorter or longer. For instance, the last total eclipse visible from Princeton, NJ was in 1478 and the next is in 2079. That's an interval of 601 years.

• However, the following total eclipse from Princeton is in 2144, after a period of only 65 years.

Eclipse Questions

• Explain the differences between a lunar eclipse and a new moon. 

• Explain why lunar eclipses only happen during the full moon. 

• Explain why lunar eclipses don’t happen every full moon.

• Explain the difference between the penumbra and the umbra. 

• Explain the difference between an Umbra Solar Eclipse and a Penumbra Solar Eclipse.

• Explain what is meant by an Annular Solar Eclipse.  Include the key term antumbra in your answer.

• Explain why solar eclipses only happen during the new moon. 

• Explain why solar eclipses don’t happen every new moon. 

• Explain what is meant by the Path of Totality. • Explain the differences between Lunar and Solar

eclipses in detail!

• What is the most common type of lunar eclipse?

• What is the most common type of solar eclipse?

• What is the most common type of eclipse (solar or lunar)?

• Which is longer: solar or lunar eclipse? What is the length of each (at most)?

Eclipses on other Planets

• An eclipse can occur on other planets.

• An eclipse occurs when one celestial object moves into the shadow of another.

• When an eclipse occurs, there is an alignment of three or more celestial bodies in the same gravitational system along a straight line

Jupiter

• Jupiter has 4 large moons.

• Jupiter has a low axial tilt.

• Jupiter’s solar eclipses are

frequent.

Saturn

• Saturn’s tilt is greater than Jupiter’s so it experiences less solar eclipses.

• Titan and Saturn exhibit similar eclipses to Earth and the Moon because their tilt is similar (27’ tilt of Saturn and Titan’s 1.6’ tilt) but these only occur every 15 years.

Mars

• Only partial solar eclipses are possible.

• Its moons are not large enough to cover the disk of the Sun.

• Total lunar eclipses are very probable on Mars.

• Also eclipses of Deimos by Phobos (2 moon system).

http://en.wikipedia.org/wiki/Eclipse#Other_planets

Mercury and Venus

• No moons so no eclipses are possible!

Pluto

• Daily solar eclipses (due to relative size of planet to moon)

• They are mutual eclipses

Eclipse Facts

• http://starryskies.com/The_sky/events/lunar-2003/eclipse5.html

• Good video review…

• http://vimeo.com/groups/skysthelimit/videos/1671764

How do Solar Eclipses and Lunar Eclipses Affect People on Earth?

• Celebrations

• Flowers – open or close

• Animals – get ready for night– Birds sing evening songs– Chickens “roost”

• In the past, this was frightening– Sacrificed animals– Offered songs, prayers, etc