The Nighttime Sky Planetarium Exercise



The Nighttime Sky Desktop Planetarium Exercise Introduction The human perception of the nighttime sky is that of looking at the inside of a hemisphere with all celestial objects arranged two-dimensionally on it. We now know that the Universe is indeed three-dimensional, but that perception of a Celestial Sphere lends itself well to a coordinate system for the sky similar to latitude and longitude. It also makes the planetarium ideal for accurately simulating the night sky. I. The Constellations and Stars Start up the Stellarium desktop planetarium software. Use the Location window on the far left edge of the Stellarium window (or Fn+F6) to set your location to Phoenix, United States. Use the Date/time window on the far left edge of the Stellarium window (or Fn+F5) to set the current date and time. Use the Sky and Viewing Options window (or Fn+F4), click on the Landscape tab, and choose Ocean on the far left to create a level horizon. While still in the Sky and Viewing Options window, click on the Markings tab, and check Equator (of date) (all boxes), Ecliptic (of date) (all boxes), and Celestial Poles (of date). Click on the Atmosphere button on the bottom edge of the window (or type “a” with your cursor anywhere in the Stellarium window) to view a dark sky even during daytime. Click on the Constellation lines button on the bottom edge of the window (or type “c” with your cursor anywhere in the Stellarium window). Click on the Constellation labels button on the bottom edge of the window (or type “v” with your cursor anywhere in the Stellarium window). Set the Date/time to this evening at 9:00 pm. Determine which of the following constellations would be visible tonight from Scottsdale. Give their approximate location in the sky for this date and time: Ursa Major Lyra Bootes Ursa Minor Leo What planets are visible tonight in the evening sky? What feature on the Celestial Sphere are they always close to? In what direction do the stars and planets move during the course of the night, when you are facing North? Where is the star Polaris in the sky? What is special about its place in the sky? Find the Moon and click on it to display a pop-up with information about the Moon. What is the phase of the Moon tonight (“Moon age”)? II. Celestial Coordinates Astronomers use the coordinate system of Right Ascension and Declination for the Celestial Sphere, similar to Longitude and Latitude for the Earth’ surface What is the Declination of Polaris? Is it the same for everyone on Earth? Through what feature in the constellation Orion does the Celestial Equator pass? Press Fn+F6 to open the Location window. Change the Current location information Latitude to 0O 00’ 00”. Close the Location window. Look due West, and use the Time rate controls on the bottom edge of the Stellarium window, to make time pass quickly enough to see the movement of the sky. Do the same looking East. At what angle to objects rise and set with respect to the horizon while viewing from the Earth’s equator? Press Fn+F6 to open the Location window. Change the Current location information Latitude to 90O 00’ 00”. Close the Location window. Look due West, and use the Time rate controls on the bottom edge of the Stellarium window, to make time pass quickly enough to see the movement of the sky. Do the same looking East. At what angle to objects rise and set with respect to the horizon while viewing from the Earth’s North Pole? Where would the Celestial Equator be in the sky if you were standing at the Earth’s Equator? If you were standing at the Earth’s North Pole? Where would Polaris be in the sky if you were standing at the Earth’s Equator? If you were standing at the Earth’s North Pole? (Hint: what is its Altitude at these locations?) Where is the Celestial Equator relative to the Ecliptic? IV. Other Questions In what direction does the Sun appear to move with respect to the stars during the course of the year? What is the apparent path the Sun takes called? How can you determine your latitude while in the Northern Hemisphere? Why do we always see the planets close to the Ecliptic (but not always exactly on it)? ................
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