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Unformatted text preview: 1/25/11 Astro 109 Lecture 3: Understanding the Sky Jan. 25 Ques@ons about reading or homework? Jan. 25 Quiz Ques@on #1 The projec@ons of the Earth's rota@on axis onto the sky are called the A. B. C. D. E. celes@al poles sols@ces zeniths celes@al equator zodiac Quiz Ques@on #2 True or false? The Sun passes through your zenith every day. A. true B. false Jan. 25 Jan. 25 Quiz Ques@on #3 The sols@ces and equinoxes are mainly associated with A. B. C. D. E. the path of the Sun through the sky. the seasons. the distance of the Earth from the Sun. both A and B. all three A, B, and C. Key Concepts mo@ons in the sky Earth's @lt <--> seasons terminology: zenith, meridian celes@al equator, eclip@c equinox, sols@ce Jan. 25 Jan. 25 1 1/25/11 Thought Ques@on This picture of Earth was taken by the Galileo spacecraY. In what month was it taken? A. B. C. D. E. March June September December There is not enough informa@on to tell. Terminology for local sky Jan. 25 Jan. 25 Sun moves--throughout day and year The Analemma Jan. 25 Jan. 25 2001-2010 Anthony Ayiomami@s Stars move, too Earth rotates Jan. 25 Jan. 25 h^p://www.planetary.org/explore/topics/earth/earth_rota@on_galileo_e1.mov 2 1/25/11 Discussion Ques@on What was the dura@on of this @me-lapse photograph? A. 1 minute B. 10 minutes C. 1 hour D. 6 hours E. 12 hours Earth's sky = Celes@al Sphere Jan. 25 Jan. 25 Local sky vs. celes@al sphere: Observer at north pole Observer at equator Jan. 25 Jan. 25 Observer in New Brunswick Discussion Ques@on The Sun rises in the east and sets in the west. Which of the following statements about the stars is true, as seen from New Brunswick? A. All stars rise in the east and set in the west. B. Some stars rise in the east and set in the west, but others are visible all night. C. All stars rise in the west and set in the east. D. Some stars rise in the west and set in the east, but others are visible all night. E. None of the above. Jan. 25 Jan. 25 3 1/25/11 Earth's @lt h^p://www.planetary.org/explore/topics/earth/earth_moon_conjunc@on_galileo.mov (a) rela@ve to celes@al sphere (b) rela@ve to eclip@c (i.e., Sun) Jan. 25 Earth's @lt and the seasons Jan. 25 Jan. 25 Seasons and Sun's path across sky Summer sols@ce: highest path; rise and set furthest north; long day, short night Discussion Ques@on Suppose the date is March 21 and the Sun passes through your zenith at noon. Where are you? A. B. C. D. E. the equator (0 la@tude) the Tropic of Cancer (23.5N la@tude) the Tropic of Capricorn (23.5S la@tude) the Arc@c Circle (66.5N la@tude) New Brunswick, NJ (40N la@tude) Winter sols@ce: lowest path; rise and set furthest south; short day, long night Equinoxes: Sun rises due east and sets due west; equal day and night Jan. 25 Jan. 25 4 1/25/11 Seasonal changes are drama@c at high la@tude Why doesn't distance from Sun ma^er? Path of Sun on summer sols@ce at the Arc@c Circle. Jan. 25 Jan.
25 Change in distance is small (3%), and is overwhelmed by effects of axis @lt Precession Discussion Ques@on This picture of Earth was taken by the Galileo spacecraY. In what month was it taken? A. B. C. D. E. March June September December There is not enough informa@on to tell. Jan. 25 Direc@on of celes@al north changes (slowly) --> Polaris won't always be the North Star Jan. 25 5 ...
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This note was uploaded on 03/24/2011 for the course PHYS 123 taught by Professor Wenkstern during the Spring '08 term at Rutgers.
- Spring '08