Motions in the Nighttime Sky and the Celestial Sphere Background Throughout time, humans have created models of the nighttime sky to help…

Motions in the Nighttime Sky and the Celestial Sphere

Background

Throughout time, humans have created models of the nighttime sky to help them predict the motions within the nighttime sky as well as the Sun throughout the year. One of the earliest models, which is still used today, is the celestial sphere. A larger model is a (physical) planetarium where the nighttime sky is illuminated over your head. While these models are very helpful, they are not easy to transport. Thus various types of star maps and planispheres have also been used over the ages. Now with technology, “planetarium software,” apps, and web pages can be used, such as Stellarium, Google Sky, and World Wide Telescope.

Like all models, these are not perfect. Rather, they are intended to help us visualize what is happening, and perhaps help us understand how or why. In this lab, we will be exploring at least one of these models.

Instructions

You will need to read this lab completely. You will be presented with questions of various types that you will need to answer on the lab report that you will upload to eCampus once complete. The student should expect this lab to take 3 hours to complete.

Section I: Motions in the Night Sky

In this section of the lab, you will be asked to go outside for observations of the nighttime sky. You will need scratch paper to help you with your observations. (Scratch paper will always be for the benefit of the student and will not be turned-in.) As always, you will want to read all directions carefully before proceeding.

While the observations can be made from anywhere at any time during nighttime, it is recommended that you choose a location that you are familiar with, and that has at least one direction where you can see down to the horizon without barriers such as buildings, mountains, et cetera. Wait at least 45 minutes after sundown to make your first observation. Then wait at least 1 hour after your first observation (and at least 1 hour before sunrise) to make your second observation. Your observations will need to take place on the same night. You will need to be sure you know with certainty the cardinal directions (north, east, south, west) from your observation location. You may find a smartphone or tablet app (like Google Sky or SkEye) helpful but not necessary. Your observations may each require up to 30 minutes for your eyes to become (mostly) dark-adjusted plus another 10 to 20 minutes to get set-up and record your observation.

Part A: Observations

Observation 1: You will need to make sure your viewing location is dark. Try to find a location with minimal lights (like the lights found in lit parking lots, along streets, or building lights). You will also need to view on a night mostly free from clouds. You will need to check weather forecasts to insure the sky does not become cloudy during your window for observations. Face a direction where you can view the horizon, but preferably not north if viewing from Earth’s northern hemisphere or south if viewing from Earth’s southern hemisphere. Using a piece of scratch paper, make a drawing of the stars you see. Be sure to include all bright stars and planets. Your drawing should include the horizon and at least 10 celestial objects you can see with your unaided (“naked”) eye. Place a circle around one bright stellar-like object that you feel you can easily find/identify at a later time. It is not necessary to identify what (stars, planets, constellations) you see. However if you happen to know or recognize anything what (stars, planets, constellations, asterisms), you may want to label it to help you identify it later. If you have a nighttime sky app, you may want to use it to help you identify a few of the bright objects you can see. After making and recording your observation, answer the following questions on your lab report.

Question 1: What direction/s did you face?

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Question 2: What time did you make your observation?

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Make predictions.

Question 3: Do you think you will be able to notice if the stars have shifted their location between the two observations? (Yes/No)

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(a)If you said “YES” to question 3 and believe they will move,

(1)In what direction do you think they will shift?

(2)Approximately how fast will they move? (Fast/Slow)

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(b)If you said “No” to question 3, explain why you think there will be no noticeable change in their relative locations.

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Question 4: How do you feel the stars’ motion will compare/look relative to the Moon during the night or the Sun during the day?

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Observation 2: After at least one hour has passed since the first observation but at least one hour before sunrise, go back to the exact same location and face the exact same direction. On you another sheet of scratch paper, sketch what you see. Again, try to find several bright objects and sketch them. Try to locate the celestial objects you first viewed and sketch them as well. Include the horizon on your sketch. Find and circle the same object you circled in your first sketch. Try to re-identify any stars, planets, constellations, or asterisms you may know and recognize. Once you have finished this observation, answer the following questions based upon your observations and sketches.

Question 5: What time did you make your 2^nd observation?

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Question 6: How much time passed between your two observations?

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Compare your two sketches

Question 7: Can you discern any shift in the location of the stars relative to the sky? (Yes/No)

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(a)If you said “YES” to question 7 and noticed they did move,

(1)In what direction did they shift?

(2)Approximately how fast will they move? (Fast/Slow)

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(b)If you said “No” to question 7, explain why you think there was no noticeable change in their relative locations.

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Question 8: How does the motion of the Moon at night or the Sun in the day compare to your observations?

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Question 9: Considering only the stellar object you circled in your observations, make an estimate of how much time it will need to set (to drop below the horizon).

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Part B: Models

In this part of the lab, you will use a model of the sky along with your sketches. You may use a celestial sphere, planisphere, planetarium, or planetarium software (but no star maps nor apps as they will not have the necessary capabilities). You will set the model to represent the same date and time of your first observation, and facing the same direction. Study the image before you until you become comfortable with it. Try to find the celestial objects you observed. With the model and your sketches in front of you, answer the following questions.

Question 10: List the 10 celestial objects you observed and placed on your sketch.

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Question 11: What is the name of the object you circled?

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Question 12: Use the model to determine what time your circled object would set.

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Question 13: Move your model to the time and date of your 2^nd observation. Comparing it to the date and time of your 1^st observation, does the model show a shift in the location of the celestial objects relative to the sky? (Yes/No)

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Question 14: Now compare your sketches to the model. Do they generally agree in where the celestial objects are located for both observations?

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Question 15: Now compare the locations of the celestial objects over the course of one night to the motion of the Moon and the Sun during the day. Do they exhibit similar motions? (Yes/No)

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Question 16: Considering your observations outside, what appears to be moving – the Earth or the stars?

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Question 17: Considering your observations of the model, what appears to be moving – the Earth or the stars?

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Question 18: What do YOU think is moving – the Earth or the stars?

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Question 19: Using a reliable resource (e.g. library, your textbook, an expert web page, etc.), find the reason for the motions of the Sun and celestial objects.

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Question 20: Did the model correctly represent the true reason for the apparent motions?

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Question 21: Did the model reproduce your observations well?

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Question 22: Was the model easy to use or learn to use?

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Question 23: Did the model cause any misconceptions?

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Section II: Celestial Sphere and Sky Maps

In this part of the lab, we will explore a set of star maps which have been provided to you free of charge on eCampus. The maps are from the Stephen F. Austin University Observatory and can be used anywhere in the world on any date and time. (Many star charts are for a specific region or nighttime calendar range.) You will notice page one is of the northern sky, much like you might see if standing on Earth’s geometric North Pole. Pages two and three are of the equatorial region, and page four is the southern pole region. Pages five and six give information necessary for and instructions on how to use the maps. Read these two pages now. If, after reading pages 5 & 6, you are desiring more information, please consider referring to your textbook (21^st Astronomy chapters 2 & 3). Once you feel comfortable with the readings, answer the following questions using ONLY the star charts provided.

Question 24: The Earth coordinates for Dallas, Texas are approximately 32° 47’ (latitude) and 96° 48’ (longitude). How far above my northern horizon should I expect to find Polaris?

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Question 25: What would I expect the radius (in degrees) of my circumpolar region be for Dallas, Texas?

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Question 26: Sketch an outline of your circumpolar region on Chart 1. Then list the 6 constellations that are located within the circumpolar region for Dallas, Texas.

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Question 27: How many degrees exist between a pole and the celestial equator?

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Question 28: How many degrees above my southern horizon is the celestial equator?

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Question 29: How high above the northern horizon is my zenith from Dallas, Texas?

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Question 30: What is the declination of my zenith point, as viewed from Dallas, Texas?

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Question 31: How many hours on a clock are in one full day (day + night)?

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Question 32: How many hours of sky can I see any time I view the nighttime sky?

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Question 33: How many hours exist between the meridian and the eastern horizon?

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Question 34: What is the RA of February 21^st’s meridian?

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Question 35: There are two sets of dates on the equatorial maps. Which ones (along the top or within the star field) should be used when looking for daytime events??

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Question 36: What constellation is the Sun in on July 4th?

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Question 37: What constellation is the Sun in on Mae Jemison’s birthday (October 17^th) based upon the (western) horoscope? (i.e. What is her “sign”?)

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Question 38: What constellation is the Sun in on Mae Jemison’s birthday (October 17^th) based upon the star charts?

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Question 39: What star is located at 6 hrs 44 mins right ascension and -16.7° declination?

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Question 40: What star is located at 5 hrs 14 mins right ascension and +46.0° declination?

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Question 41: What star is located at 5 hrs 13 mins right ascension and -8.2° declination?

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Question 41: What star is located at 13 hrs 23 mins right ascension and 55.1° declination?

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Question 42: What star is located at 16 hrs 28 mins right ascension and -26.4° declination?

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Question 43: What are the coordinates for the star Castor in the constellation Gemini?