AST 105 Motion of The Moon Lab Exercise Questions

Lab Exercise: Motion of the MoonDuring this lab we will study the phases and motion of the moon. We will examine the phenomenon of eclipses.
Finally, we will discuss the rotation of the moon.
Lunar Phases
Using the diagram below, sketch what the moon will look like from Earth in each configuration and label the
phase (Example: full moon, waxing gibbous….)
For each configuration below, discuss what time you would expect the moon to rise, cross the celestial meridian,
and set.
Configuration
1
3
5
7
Moonrise
Crosses the celestial meridian Sets
Lunar Orbit
Define the following terms including the length of each in days:
Sidereal Month-
Synodic Month-
Which month coincides with the phases of the moon?
Which month is longer and why? (Hint: A picture showing the position of the moon, earth, and sun from one
month to the next might help)
Eclipses
What is a solar eclipse? What phase will the moon be during a solar eclipse?
What is a lunar eclipse? What phase will the moon be during a lunar eclipse?
The following image describes the moon’s orbit around the earth. Given this image, why don’t we observer an
eclipse every month? Given that we do from time to time observe an eclipse, does this imply that the nodes of
the moon’s orbit are stationary or do they also orbit the earth? Note the nodes are the points where the moon’s
orbit crosses the plane of the earth’s orbit around the sun.
The moon is gravitationally locked with the Earth (you’ll need to look up that term if you aren’t familiar with it).
Draw a diagram illustrating why this means there is no “dark side” of the moon. Please note this should be your
original work, not copied and pasted from another resource.
Lab Exercise: Orbits
The goal of this lab is to study the orbits of solar system objects and note the effect they have on the
host star and each other.
For this lab, please navigate to the following website:
https://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html
2 Body Problems
Set the number of bodies to 2. All scenarios should be set to the highest accuracy. Then set the values
as follows
Mass
Position
x
Velocity
y
x
y
Body 1
200
0
0
0
0
Body 2
0.001
-51
0
0
-194
How would you describe this orbit? Is it circular or and ellipse? Is it stable or unstable? Is the sun
stationary or moving?
Now change the mass of body 2 to 10. You’ll need to click reset to be able to change this. How would
you describe this orbit? Is it circular or an ellipse? Is it stable or unstable? Is the sun stationary or
moving?
Now for Body 2, change the x position to 150, and the y velocity to 120. How would you describe this
orbit? Is it circular or and ellipse? Is it stable or unstable? Is the sun stationary or moving?
Based on your observations, how does the mass of the orbiting planet affect the star? How does the
distance between the planet and star affect the star?
How might you use this information to detect the presence of planets around other stars? (Hint:
research the topic doppler wobble)
3 Body Problems
Note that the 3 body problem is not accurately solvable by physics. So this simulation provides an
estimate. Select the 3 body button.
Set the following conditions
Position
Velocity
Mass
x
y
x
y
Body 1
200
0
0
0
0
Body 2
1
150
0
0
120
Body 3
0.001
-50
0
0
-200
Are the orbits stable? Are the orbits exactly the same each time around the sun? What is the effect on
the sun?
Now set body 3 to the following settings, x position -100, y position 0, x velocity 0, y velocity -150. Do
the planets affect eachothers orbits? How and why?
Now set the following conditions and turn the simulation to the fastest setting.
Position
Velocity
Mass
x
y
x
y
Body 1
200
0
0
0
0
Body 2
1
150
0
0
120
Body 3
0.001
-400
0
0
-67
How does the larger planet affect the orbit of the smaller planet? How might this be relevant to comets
and asteroids in our solar system?
Given the stable orbits you observed, what is the relationship between the distance between the planet
and the sun, and the velocity of the planet?
Consider a situation where a planet is orbiting a star. Would it be easier to detect the planet’s presence
when the planet is close to the star or far from the star? Why?
Would it be easier to detect a small or large planet? Why?
Currently most of the planets detected around other stars are large and close to their sun. Is this a good
representation of the most common planets around other stars?