Download THE MOON

THE 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 Moon
Waxing Crescent
First Quarter
Waxing Gibbous
Full Moon
Waning Gibbous
Third Quarter
Waning 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 nighttime 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=IVkkCV
h5t0E
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=C4b7KC
FpJAI&feature=PlayList&p=0F9169A2DC5
724F9&playnext_from=PL&index=5&playn
ext=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/luna
r-2003/eclipse5.html
• Good video review…
• http://vimeo.com/groups/skysthelimit/video
s/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