AST201L

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Astronomy

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Dec 6, 2023

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Outdoor sky-watching exercise NAME & USERNAME: ALEXANDRA BRISTER SECTION: 011 LAB 11 STARS AND TIME INTRODUCTION This entire lab requires outdoor observing of the night sky. This lab focuses on the diurnal movement of stars in the night sky as they circle around the North Celestial Pole. You will learn to identify prominent stars and constellations in the early part of the winter night sky and to track their movement. You will also estimate angular distances in the sky using your hands at arm’s length. Recall the helpful apps and websites ( i.e., Stellarium ) from Lab 1 that you might want to use to help you in this lab. In this lab, you will learn about the Navajo, or Diné, Constellations, and their stories. In Diné culture, these stories, as well as the Origin Story, are part of their Winter Stories, which are only proper to tell during winter time, from the first snow to the first lightning (roughly September to March) . Please remember that this lab is taught at this time (if outside of Sep. to Mar.) only for educational purposes. Let us respect Diné culture and history together, and learn how Diné people seek harmony with the sky and nature. LEARNING GOALS The points below are the expected topics to understand by the end of this lab period. Remember to review these points before completing the lab. If you do not understand one, review the steps that cover it and discuss with your instructor.  Learn to identify and name constellations  Learn to measure angles on the night sky  Learn three important Navajo constellations and their significance in the night sky LAB11-1

Figure 7.1: The Big Dipper, Cassiopeia, the North Star (Polaris) and the Little Dipper as seen in early winter evening in the Northern Hemisphere a Figure 7.2: The size and distances between objects in the sky are typically given as a measure of their angular distance as seen from Earth. These NAME & USERNAME: ALEXANDRA BRISTER SECTION: 011 STEP 1: FINDING NÁHOOKÒS CONSTELLATIONS To get started, find a place where you have a relatively clear, dark view of the night sky. Face north, approximately in the direction of the San Francisco Peaks. If it is early evening in winter, the Big Dipper will appear low in the sky to your left (towards the West). The North Star (Polaris) is at the end of the handle of the Little Dipper. The Little Dipper is more difficult to see in general, since many of its stars are faint. The Big Dipper, however, is much more recognizable, and two “pointer stars” at the end of the cup point to the North Star as shown in Figure 7.1. The Navajo interpretation of the Big Dipper is the “Male Revolving One” or Náhookòs Bi’kà’ii (pronounced Na Hoe kos bi kah ee– Practice pronouncing this and point it out to someone else if you get the chance!). To the Navajo, Náhookòs Bi’kà’ii is a male warrior and leader who protects his people and is pictured as lying on his side. He is sympathetic, charismatic, and a provider for his family and home. As a father, he provides spiritual and physical protection, and he is always paired with his female counterpart Náhookòs Bi’áádii (pronounced Na hoe kos Bih aad ee – more below). The North Star is known to the Navajo as the “Central Fire” or Náhookòs Bikò‘ (pronounced Na hoe kos Bih kwo) and symbolizes the central hearth in a Navajo Hogan. Describe your location here (city, location in the city, coordinates if you have them): Flagstaff, AZ south of NAU campus, (35.18, -111.64) LAB11-2

Figure 7.4: Using your fist to measure an a Zenith 80o 7 0 o 6 0 o Figure 7.3: Angular distances between the stars of Náhookòs Bi’kà’ii for use in calibrating the width of fist and fingers held at arm’s distance. NAME & USERNAME: ALEXANDRA BRISTER SECTION: 011 STEP 2: MEASURING ANGLES ON THE SKY After you have confidently identified Náhookòs Bi’kà’ii and Náhookòs Bikò‘, you will be ready to use them to measure angles in the sky (See Figure 7.2). Holding your hand at arm’s length, the angular distance that you can measure with your thumb finger is typically one degree. With that finger, you can cover two moons. Your three middle fingers cover the distance of 5°; with your fist, you can measure 10° in the sky; and the angular distance from the tip of your index finger to the tip of your pinky finger is 15°. These lengths are only approximate, however, because arm lengths and finger sizes vary from person to person. To be more precise, you must calibrate your hand and finger measurements by comparing them to stars separated by known angles! Use the above figures to determine the angular width of 1) your fist and 2) the total width of your 3 middle fingers with your palm open. Compare your fist at arm’s length with different pairs of stars in the Big Dipper as indicated in Figure 7.3 1 . Find which pair best matches your fist and add or subtract degrees or fractions of a degree to account for any slight differences. 1. What is the angular width of your fist at arm’s length, in degrees? [0.5pt] 2. What is the angular width of your middle 3 fingers? [0.5pt] The farthest of the Pointer Stars from the North Star is called Merak (see Figure 7.1). Use your fist to estimate the angular distance from Merak to the North Star (Náhookòs Bikò‘). Use a method similar to that pictured in Figure 7.4 above. 3. How many of your fists fit from Merak to Náhookòs Bikò‘? [1pt] 4. What is the angular distance from Merak to Náhookòs Bikò‘ in degrees then? [1pt] 1 This NASA Night Sky Notes article, Measure the Night Sky (Nov, 2021), has a nice figure of the angular distances of the Big Dipper: https://nightsky.jpl.nasa.gov/docs/NightSkyNotesNov2021MeasureTheNightSky.pdf . LAB11-3

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