Motion of the Sun motion relative to the horizon rises in the east, sets in the west on a daily basis Basis for the unit of time, the DAY noon: highest point of Sun in sky relative to the horizon 1
altitude: angular height of the Sun above the horizon altitude depends on your latitude on Earth What is the speed of the Sun s motion, relative to the horizon? 2
Motion of the Sun North and South motion along the east or west horizons seasonal Kaufmann & Comins 4/e 3
Summer Solstice - June 21 rises farthest north of east on horizon most hours of daylight highest altitude (68 degrees here) Autumnal Equinox - September 21 rises directly east, sets directly west Sun is moving along east & west horizons from north to south (going southward) equal amounts of day and night hours 4
Autumnal Equinox - September 21 rises directly east, sets directly west Sun is moving along east & west horizons from north to south (going southward) equal amounts of day and night hours Winter Solstice - December 21 rises farthest south of east on horizon fewest hours of daylight lowest altitude (22 degrees here) 5
Vernal Equinox - March 21 rises directly east, sets directly west Sun is moving along east & west horizons from south to north (going northward) equal amounts of day and night hours Cycle defines the unit of time, the YEAR 6
Motion of the Sun motion relative to the stars on a yearly basis, the sun s apparent motion, with respect to the background stars is ~ 1 degree per day eastward zodiac: 12 constellations through which the Sun appears to move over the course of a year ecliptic: path of the Sun through the zodiac 7
What is the Sun s angular speed with respect to the background stars? How can you figure that out? 8
Motion of the Moon motion relative to the horizon rises in the east, sets in the west on a daily basis motion relative to the stars monthly basis moves eastward through the zodiac one complete cycle in 27 days 9
What is the angular speed of the moon s eastward motion through the zodiac? angular speed of the moon = 360 o 27 days = 0.5 o hour THAT you can easily see!! 10
Motion of the Moon, Relative to Venus Tulsa, OK - 1988 - Zeilik 6/e Exposures, 10 min. apart Note: moon s motion to the east (upward, left) with respect to Venus 11
Lunar Phases Kaufmann & Comins 4/e cycle of phases determines the unit of time, the MONTH phase = how much is illuminated 12
Lunar Phases FULL - directly across from the Sun Each day the moon is approximately 50 minutes later than it was the day previously. 13
Lunar Phases 3rd Quarter : 7 days after the full moon What time does 3rd Quarter moon rise? (with respect to sunset) 3rd Quarter moon is half illuminated illuminated half facing east (Sun) 14
Lunar Phases NEW: very near the Sun no illumination What time does the new moon rise? 15
Lunar Phases 1st Quarter: 7 days before full moon What time does 1st quarter moon rise? (with respect to sunset) half-illuminated, illuminated half faces west 16
Lunar Phases crescent: very thin slice gibbous: almost full waxing: going towards full waning: going away from full 17
Eclipses Solar Eclipse: moon passes in front of the Sun moon blocks the light of the Sun only those places on Earth in the direct path see the eclipse 18
Solar Eclipse Kaufmann & Comins 4/e 19
Solar Eclipse What phase must the Moon be in for a solar eclipse to occur? 20
Annular Solar Eclipse - APOD Total Solar Eclipse - APOD 21
Eclipses Lunar Eclipse: moon passes into Earth s shadow everyone on night side of Earth gets to see it 22
Lunar Eclipse Kaufmann & Comins 4/e 23
Lunar Eclipse What phase must the Moon be in for a lunar eclipse to occur? 24
Lunar Eclipse - APOD 25
- APOD CONCEPT EXTENSION: What is occurring on Jupiter? 26