Celestial Motion Experiment A02

To review various astronomical topics: Celestial Motion, Constellations, Causes for the Seasons, and the Lunar Cycle

Materials

Computer with Internet Access

Procedure

Part A: Celestial Motion

During this portion of the lab you will explore some of the same concepts that you just saw on the planetarium dome. We will be using simulations that have been created at the University of Nebraska-Lincoln. You can use either the lab computers or you can use your own laptop by visiting the website

http://astro.unl.edu/animationsLinks.html

You will be using the simulation Rotating Sky Explorer. This simulation has two views: the left view shows the celestial sphere and how the Earth spins within it, the right view is your view from the ground and how you see the celestial sphere move (similar to what you saw on the dome earlier in the lab). Take a few minutes to familiarize yourself with how the simulation works and then answer the questions below.

(Hint: Things to try with the simulation are to change your location on the Earth, drag around the globe, add stars to the celestial sphere, and add star trails. Make sure you click the Start Animation button to see the simulation run.)

1. Why do all objects on the celestial sphere rise in the east and set in the west? (This answer requires much more detail than just, “Because the Earth rotates.”)

All objects rise east and set west because the earth rotates counter clockwise.

2. Set the location to Norfolk, (latitude = 36.9° N, longitude = 76.2° W). From this location:

a. Are there stars that never rise?

Yes

b. Are there stars that never set?

Yes

c. Are there stars that are always up? (What is the name for this type of star?)

Yes, circumpolar.

3. From Norfolk, what direction do you have to look to see circumpolar stars?

North

4. As you increase your latitude do you see more or less circumpolar stars? As you decrease your latitude do you see more or less circumpolar stars?

As latitude increases there becomes more circumpolar stars. As latitude decreases there becomes less circumpolar stars.

5. What do you think the motion of the stars would look like if you were at the North Pole? Where would Polaris (the North Star) be located?

The stars wouldn’t rise or set and appear clockwise. The Polaris would be directly overhead.

6. What do you think the motion of the stars would look like if you were at the Equator? Where would Polaris be located?

The motion of the stars would rise eat and set west. The Polaris star would be laying on the northern horizon.

Part B: Constellations

(For the following questions, just name 2 or 3 constellations that would be highest in the sky.)

1. What constellations would be directly overhead at midnight in late January?

Cancer

2. Find the Earth’s orbital position associated with your birth date (and indicate your birth date below). What Zodiac constellation does the Sun appear to be “in” on your birthday?

My birthday is April 22nd, so the sun would appear in the Aries zodiac constellation.

3. If the Sun didn’t shine so brightly, what Zodiac constellations would you see overhead around noon on your birthday?

I would see the Aries zodiac constellation.

4. What Zodiac constellations are overhead around midnight on your birthday?

Libra is overhead at midnight on my birthday.

5. What Zodiac constellations are overhead around midnight 6 months after your birthday?

Aries would be overhead at midnight six months after my birthday.

6. Based on your above work, explain why the night sky changes seasonally. (This answer requires much more detail than just, “Because the Earth orbits the Sun.”)

As the earth orbits the sun, the sun blocks us from viewing the constellations.

Part C: Reasons for the Seasons

Northern Spring/ Southern Fall

Northern Summer/ Southern Winter Northern Winter / Southern Summer

Northern Fall / Southern Spring

1. Draw arrows in the diagram to indicate the direction the Earth travels around the Sun.

Counter clockwise

2. Label Northern spring, summer, fall, and winter.

3. MonthEarth-Sun DistanceMarch149 million kmJune152 million kmSeptember150 million kmDecember147 million km Label Southern spring, summer, fall, and winter.

4. The distance between the Earth and Sun during 4 months of the year are listed in the chart to the right. Based on this data, what can you conclude about the effect that the Earth-Sun distance has on the seasons? Support your conclusion by citing specific data.

I can conclude that the distance has no effect on earths season because during the summer it shows that the earth is 5km farther from the sun than in the winter months, which shows that the distance doesn’t have an effect on the seasons, but the tilt has an effect on it.

5. Describe, in your own words, what causes the seasons. Specifically, why does the tilt of the Earth’s axis result in some warmer months and some cooler months?

The tilt during the summer is letting in more direct light as when in the winter the angle of the sun showing isn’t as direct. During the summer we get more sun light because there are more days, so we are exposed to the sunlight longer in the summer, which leads to it being warmer rather than in the winter months.

6. If, somehow, the Earth’s tilt changed from 23.5° to just 5°, what would change about the seasons?

The intensity of the seasons would increase.

Part D: The Lunar Cycle

In this portion you will be using the simulation Lunar Phase Simulator which is located at

http://astro.unl.edu/animationsLinks.html

This simulation is a top-down view of the Earth looking at the North Pole. It can also show the position of the Moon in its orbit and the associated phase. Take a few minutes to familiarize yourself with how the simulation works, combine what you see in the simulation with the diagram below, and then answer the questions.

1. What Moon phase will an observer see if the Moon is directly overhead at sunset?

First Quarter

2. What Moon phase will an observer see if the Moon is directly overhead at sunrise?

Third Quarter

3. What Moon phase can be seen for half of the night and then half of the day?

Third Quarter

4. What Moon phase can be seen for half of the day and then half of the night?

First Quarter

5. The following sketches of the moon's appearance were made over about four weeks. Identify the phases and put them in the correct numerical order (full Moon is considered as 0, the starting point). One is labeled for you.

PictureOrderPhasePictureOrderPhaseA Wanning CrescentDFirst QuarterB1Wanning GibbousEWaxing GibbousCFull MoonFWanning Crescent

6. In the diagram below the sun's light is coming in from the right. The moon's location is marked at several points on its orbit. These are the points the moon was at when the sketches above were drawn. Identify each position with the letter of the corresponding sketch.

D

A F B C E

7. How long does it take the Moon to complete one cycle of phases, in days? About 29.5 Days

8. If the Moon is full today, what phase do you expect it to be at in a week?

Third Quarter

9. How about one month later?

Full Moon

10. Is there a dark side of the Moon? (Note: this question can be effectively answered either yes or no, so it is important to thoroughly explain your reasoning.)

No, because the sun is always shining at the moon, therefore there’s always a night time and day time of the moon.