Study Guide for Midterm 1
Study Guide for Midterm 1 AST 101 - M001
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AST 101 - M001
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This 4 page Study Guide was uploaded by Mitchell Jones on Sunday September 20, 2015. The Study Guide belongs to AST 101 - M001 at Syracuse University taught by C. Armendariz-Picon in Fall 2015. Since its upload, it has received 186 views. For similar materials see Our Corner of the Universe in Astronomy at Syracuse University.
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Date Created: 09/20/15
Celestial Sphere Stars are so far away to naked eye seem same distance Imaginary sphere on which stars lie Star Theater Stars are projector that shine through screen celestial sphere to people Constellations Patterns of stars on celestial sphere Represent regions of sky or celestial sphere like counties or states of sky Cannot see stars on celestial sphere below the horizon where ground meets the sky Horizon in boundary of celestial sphere because the difference between a person s perspective and the horizon are negligibly small compared to the size of celestial sphere Motion of the Night Sky Latitude measured as NorthSouth lines go eastwest Distance from equator Determines climate Altitude angle between celestial pole and horizon of Polaris is equal to your latitude Longitude measured as Eastwest lines go Northsouth Distance from prime meridian Greenwich England Stars move counterclockwise around Polaris as seen from earth Stars rise in east and set in the west Circumpolar stars that are always visible never rise or set Motion of the Sun The earth spins celestial sphere is imaginary it does not spin stars in fixed position and earth rotates underneath Earth spins counterclockwise Sun Is also represented by celestial sphere Rises in the east sets in the west as earth spins counterclockwise Noon sun is at highest position in the sky directly south As year progresses the sun travels counterclockwise along the celestial sphere Path the sun takes along the celestial sphere is known as the ecliptic Zodiacal constellations constellations ecliptic travels through Difference between the ecliptic and the celestial equator 235 degrees The Motion of the Night Sky Continued Celestial sphere rotates onceday Sun moves along ecliptic onceyear Sumer solstice June 21 longest day of the year sun highest in the sky Autumnalfall equinox September 21 12 hours da 12 hours night Winter solstice December 21 shortest day of the year sun lowest in the sky Vernalspring equinox March 22 12 hours day 12 hours night In reality the orbit of the sun on the ecliptic is because of the orbit of the earth around the sun The difference between the ecliptic and the celestial equator is due to earth s titled axis Earth revolves counterclockwise around the sun Two simultaneous motions Earth spins counterclockwise on axis making the celestial sphere appear to spin counterclockwise Earth orbits sun counterclockwise sun moves counterclockwise around celestial sphere Motion of the Planets Sidereal day Time it takes stars to complete one full cycle through the sky Time it takes the planet to rotate 360 degrees 23 hours 56 minutes on earth Solar day Time it takes the sun to return to the highest position in the sky 24 hours on earth Longer than sidereal day because earth has to rotate an extra amount to return to face the sun earth is orbiting as it rotates Wanderers Planets or wanderers rise in the east and set in the west but also seem to move across celestial sphere like the sun Planet comes from Greek planan to wander Retrograde motion when a planet appear to travel backwards across celestial sphere observed over weeksmonths retro to go back reveals illegitimacy of the celestial sphere Early explanations for retrograde motion Ptolomaeic Model Earth centered geocentric Epicycle the planet does loops while rotating around the earth Inaccurate doesn t explain the phases of venus Sun centered model heliocentric Innerplanets orbit fast than outerplanets Retrograde motion occurs because earth passes the other planets in orbit making them appear to travel backwards as earth gets closer then back again as it passes
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