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ASTR101: Introduction to Astronomy

Unit 2: The Celestial Sphere   In this unit, you will be introduced to the celestial sphere, the physical model the Greeks used to understand celestial phenomena.  Its essential feature is that, in addition to the fixed stars, it contains seven wanderers: the sun, the moon, Mercury, Venus, Mars, Jupiter, and Saturn.  These wanderers wander through the fixed stars in an orderly way to produce the observed celestial events, including the phases of the moon and eclipses.

Unit 2 Time Advisory
This unit will take approximately 7 hours to complete.

☐    Subunit 2.1: 2 hours

☐    Subunit 2.2: 3 hours

☐    Assessment: 2 hours

Unit2 Learning Outcomes
Upon successful completion of this unit, the student will be able to: - Define the following: ecliptic, zodiac, celestial equator, winter solstice, autumnal equinox, summer solstice, and vernal equinox. - Draw and label a diagram that explains why the earth experiences seasons and why the seasons are reversed in the northern and southern hemispheres. - Draw and label a diagram that explains the phases of the moon. - Draw and label diagrams that explain lunar and solar eclipses.

2.1 The Celestial Sphere   - Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “The Celestial Sphere” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “The Celestial Sphere” (HTML)

 Instructions: This is an introduction to some basic terminology
used in discussing the celestial sphere.  

 Reading this article should take approximately 15 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

2.1.1 The Celestial Coordinate System   - Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Celestial Coordinate System” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Celestial Coordinate System” (HTML)

 Instructions: This is a more detailed treatment of the celestial
coordinate system than what was presented in the previous article.
 Most students find the coordinate system a little confusing.  Don’t
worry too much about the units used for Right Ascension; just focus
on the coordinate system and understanding the parallels between it
and latitude and longitude on earth.  

 Reading this article should take approximately 20 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

2.1.2 The Celestial Equator, the Celestial Poles, the Ecliptic, and the Zodiac   - Reading: Deep Creek Yacht Club’s “The Celestial Equator” Link: Deep Creek Yacht Club’s “The Celestial Equator” (HTML)

 Instructions: This is a very brief description of the celestial
equator.  

 Reading this article should take less than 5 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Reading: National Aeronautics and Space Administration: David P. Stern’s “The Path of the Sun, the Ecliptic” Link: National Aeronautics and Space Administration: David P. Stern’s “The Path of the Sun, the Ecliptic” (HTML)

    Instructions: This is a brief article that will introduce you to the ecliptic and the zodiac.  In the summer, the sun is further north on the celestial sphere; therefore, for people in the northern hemisphere, it is above the horizon for more than 12 hours per day.  The reverse is true in winter.

    Reading this article should take approximately 10 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

2.1.3 The Solstices, Equinoxes, and the Seasons   - Reading: Arctic Library’s “Guide to Equinoxes and Solstices” Link: Arctic Library’s “Guide to Equinoxes and Solstices” (HTML)

 Instructions: This is a very brief set of definitions for equinoxes
and solstices.  

 Reading this article should take less than 5 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “The Seasons” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “The Seasons” (HTML)

    Instructions: This article provides an explanation of why the earth experiences seasons.  It points out several common misconceptions about the cause of seasons.

    Reading this article should take approximately 20 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Web Media: YouTube: Ignite! Learning’s “What Causes Earth’s Seasons” Link: YouTube: Ignite! Learning’s “What Causes Earth’s Seasons” (YouTube)

    Instructions: This video is a nice visual explanation of the seasons.

    Watching this video should take less than 5 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

2.2 The Phases of the Moon   2.2.1 The Causes of the Phases of the Moon   - Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Orbit and Phases of the Moon” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Orbit and Phases of the Moon” (HTML)

 Instructions: This article presents a nice diagram that explains
the phases of the moon.  It also introduces you to the terms apogee
and perigee in describing orbits around the earth.  

 Reading this article should take approximately 10 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Web Media: YouTube: Park View Science’s “The Phases of the Moon” Link: YouTube: Park View Science’s “The Phases of the Moon” (YouTube)

    Instructions: This video explains the phases of the moon.

    Watching this video should take approximately 10 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

2.2.2 Solar and Lunar Eclipses   - Web Media: YouTube: FactFrog’s “Eclipses” Link: YouTube: FactFrog’s “Eclipses” (YouTube)

 Instructions: This video provides a very complete explanation of
partial eclipses.  

 Watching this video should take less than 5 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Solar Eclipses” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Solar Eclipses” (HTML)

    Instructions: This article explains solar eclipses and provides some nice illustrative animations.

    Reading this article should take approximately 15 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Lunar Eclipses” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Lunar Eclipses” (HTML)

    Instructions: This article is a companion to the earlier one about solar eclipses.

    Reading this article should take approximately 15 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Reading: National Weather Service Weather Forecast Office’s “Solar and Lunar Eclipse Page” Link: National Weather Service Weather Forecast Office’s “Solar and Lunar Eclipse Page” (HTML)

    Instructions: This article includes descriptions of solar and lunar eclipses and provides data on future eclipses up through 2018.

    Reading this article should take approximately 15 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Assessment: The Saylor Foundation’s “Unit 2 Assessment” Link: The Saylor Foundation’s “Unit 2 Assessment” (PDF)

    Instructions: When you have finished the entire unit, please complete this assessment without referring to the readings.  When you are finished with the assessment, you can check your answers against the Saylor Foundation’s “Unit 2 Assessment – Answer Key” (PDF).

    Completing this assessment should take approximately 2 hours.