Week 5 - Eclipses
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Mt San Antonio College *
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Course
5
Subject
Astronomy
Date
Dec 6, 2023
Type
docx
Pages
5
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Eclipses
1.
Consider the location of the Sun and Earth in the picture below.
Draw in the Moon where it
needs to be in order to have a
solar
eclipse.
The Moon needs to be in between the Sun and the Earth.
MOON
2.
Based on your diagram above, do solar eclipses occur during the day or night?
Explain your
answer.
Solar eclipses must occur during daytime – the Sun must be up in the sky in order
for us to see it get blocked by the Moon.
If a solar eclipse occurs when it is nighttime for a
given location, they will not see the eclipse.
3.
Not every solar eclipse that occurs on Earth is the same.
This is partly due to the distance
between the Earth and Moon.
Consider three recent solar eclipses:
Date
Distance from the
Earth to the Moon
Angular Size of the
Moon (in degrees)
Type of Solar Eclipse
July 22, 2009
356,873 km
0.558
o
Total
May 20, 2012
404,680 km
0.492
o
Annular
August 21, 2017
372,395 km
0.535
o
Total
a)
For each eclipse calculate the angular size of the Moon.
Record your answers in the table
above.
The diameter of the moon is 3,476km.
Here’s the equation from the Angular Size lab to
help you:
Angular Size (in degrees) = Diameter
x
57.3
Distance
b)
While the distance from the Earth to the Sun changes slightly, for all three eclipses in the
table, the angular size of the Sun during all three of these eclipses is 0.525
o
.
For each eclipse,
tell what type of solar eclipse it is:
total or annular
.
Record your answers in the table and
explain your reasoning below.
If the angular size of the Moon is larger than the angular size of the Sun then the Moon will
be able to block out the Sun and cause a total eclipse.
Otherwise, there will be an annular
eclipse.
Sun
Earth
c)
You should have found 2 eclipses were total eclipses.
Predict which one will have the
longest period of totality (when the Moon is completely blocking the Sun) assuming that you are
in the best place on Earth for viewing each eclipse.
Explain your answer.
The eclipse on July 22, 2009 will have a longer totality because the Moon’s angular size is
bigger.
This means that a larger shadow will fall on the Earth, causing a longer totality for
the eclipse.
4.
Imagine that you went to see the total eclipse that occurred on August 21, 2017.
Here is a graph showing you the path of the total eclipse and the areas where a partial eclipse is
visible.
The light blue lines indicate the percentage of the Sun that is blocked at each location.
Use the graph to complete the following chart.
D
B
C
A
Location
Distance from
Eclipse Center
% of Sun
Blocked
Duration of
Totality
Eclipse Center
0 miles
100%
2m 1s
Albany, Oregon
8 miles
100%
1m46s
Corvallis,
Oregon
16 miles
100%
1m13s
McMinnville,
Oregon
27 miles
100%
0m56s
Seattle,
Washington
(Location A)
196 miles
92%
-------
San Francisco,
California
(Location B)
486 miles
81%
--------
Los Angeles,
California
(Location C)
741 miles
67%
`--------
Mexico City,
Mexico
(Location D)
1765 miles
40%
--------
a)
What happens to the amount of the Sun that is blocked as you get farther away from
the eclipse center?
The farther away from the eclipse center, the less of the
Sun that is blocked.
b)
For the locations that had total eclipses, what happened to the duration of totality as
you got farther from the eclipse center?
Explain why this makes sense.
The farther from the eclipse center, the shorter the duration of totality.
This
makes sense because the farther you get away from the eclipse center, the less of the
shadow of the Moon that falls on the Earth.
The less shadow, the shorter the total
eclipse.
c)
Using the data in the table, estimate the maximum area that gets a total eclipse at any
one time during this eclipse.
Explain your reasoning.
27 miles from the eclipse center just barely has a total eclipse, but 196 miles
does not.
This means that perhaps 50 miles or so away from the eclipse center will
have a total eclipse.
The total area will be twice this because you can get the eclipse
on either side of the eclipse center;
therefore the maximum area is probably around
50 x 2 = 100 miles.
d) Your answer to c) should have been less than the 150 miles that we learned in class.
Why is this?
The 150 miles would occur if the Moon was as close as it ever
gets to the Earth.
However, on Aug. 21, 2017, the Moon is not at its closest, so the
eclipse should be seen over a smaller than 150 mile area.
e)
Look back at the eclipses you studied on the first page of this lab.
Do you think the
eclipse on July 22, 2009 had a larger or smaller area that gets a total eclipse at any
one time?
Explain your reasoning.
Larger area since the Moon is closer to
the Earth.
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6.
Let’s look a little bit at lunar eclipses now.
In the diagram below, draw where the Moon
would be during a lunar eclipse.
Must be on the opposite side of the Earth from the Sun
because the Earth’s shadow falls on the Moon.
Moon
7.
Based on your diagram above, do lunar eclipses occur during day or night?
Explain your
answer.
Night – to see a lunar eclipse we must be on the side of the Earth that is facing
away from the Sun, which makes it nighttime.
8.
Imagine that you could go to the moon during a lunar eclipse.
Describe what a lunar eclipse
would look like if you were on the Moon.
A lunar eclipse on the Moon would look like a solar eclipse from the Earth.
You would see
the Earth covering the Sun and the sky would darken and turn red because only the red
light from the Sun gets bent enough by Earth’s atmosphere to reach the Moon.
It would
look like a red ring was surrounding a dark Earth.
Sun
Earth