You Know Astronomy! Observing the motions of Sun, Moon, Stars Observing the motions of Sun, Moon, Stars Observing the appearance of the Sun, Moon, Stars Observing the appearance of the Sun, Moon, Stars Observing the passage of time Observing the passage of time

Celestial Motions Sun, Moon and Stars appear to rise in the East and set in the West daily Sun, Moon and Stars appear to rise in the East and set in the West daily Actual motion is the rotation of the Earth from West toward East daily Actual motion is the rotation of the Earth from West toward East daily Solar Day-Noon to Noon Solar Day-Noon to Noon Time Zones Time Zones

SEASONS Why do we have seasons?

The Answer The Earth is Tilted on it’s axis by 23.5º The Earth is Tilted on it’s axis by 23.5º During certain times of the year, we receive more direct sunlight since we are tilted toward the Sun (Summer) During certain times of the year, we receive more direct sunlight since we are tilted toward the Sun (Summer) Other times we receive less direct sunlight since we are tilted away from the Sun (Winter) Other times we receive less direct sunlight since we are tilted away from the Sun (Winter)

Seasons

Equinoxes and Solstices Autumnal and Vernal Equinox occur in September and March respectively Autumnal and Vernal Equinox occur in September and March respectively Equinox “Equal Night” Equinox “Equal Night” Summer Solstice Longest Day Summer Solstice Longest Day Winter Solstice Shortest Day Winter Solstice Shortest Day These rules are for Northern Hemisphere ! These rules are for Northern Hemisphere !

Seasonal Sun Does the sun appear at the same location in the sky at “noon” from season to season? Does the sun appear at the same location in the sky at “noon” from season to season? No! How does it change? No! How does it change? Pg. 8 of Text demonstrates this Pg. 8 of Text demonstrates this Tilt of Earth affects the location of Sun Tilt of Earth affects the location of Sun

Seasonal Sunset The tilt also affects the location of the sunrise and sunset The tilt also affects the location of the sunrise and sunset Pg. 9 of Text Pg. 9 of Text Sun’s position moves Southward approaching the Winter Solstice Sun’s position moves Southward approaching the Winter Solstice It moves Northward approaching the Summer Solstice It moves Northward approaching the Summer Solstice Think about the motion during the course of the year Think about the motion during the course of the year

Larger Motions Notice the night sky during different times of the year Notice the night sky during different times of the year Different star groupings are visible at night during different times of the year Different star groupings are visible at night during different times of the year Why? We are orbiting the Sun! Why? We are orbiting the Sun! Year-time for one complete orbit around the Sun by the Earth Year-time for one complete orbit around the Sun by the Earth

Other Larger Motions During the course of the year both the Sun and Moon appear to be moving Eastward compared to the background stars During the course of the year both the Sun and Moon appear to be moving Eastward compared to the background stars Sun –due to Earth’s orbit Sun –due to Earth’s orbit Moon –due to it’s orbit` Moon –due to it’s orbit`

What’s Your Sign? Constellations- Apparent 2-D pictures Constellations- Apparent 2-D pictures Zodiac-12 constellations that are special Zodiac-12 constellations that are special Lie along Ecliptic, the apparent path of the Sun through the sky due to the tilt of the Earth Lie along Ecliptic, the apparent path of the Sun through the sky due to the tilt of the Earth

Sun in Leo When we identify the Zodiac constellations we reference the position of the Sun When we identify the Zodiac constellations we reference the position of the Sun Can we actually see Leo from the earth during the month of August? Can we actually see Leo from the earth during the month of August? No, the Sun is much too bright! No, the Sun is much too bright! We need to wait until later Winter to see Leo in the nighttime sky We need to wait until later Winter to see Leo in the nighttime sky

Phases of the Moon Why do we see the phases of the Moon ?

Answer The relative positions of the Earth, Moon, and Sun The relative positions of the Earth, Moon, and Sun Waxing- Moon is getting brighter (New to Full) Waxing- Moon is getting brighter (New to Full) Waning-Moon is getting darker (Full to New) Waning-Moon is getting darker (Full to New) Month-one complete phase cycle of the moon Month-one complete phase cycle of the moon

Moon Bow and Arrow The lighted portion of the Moon always points toward the Sun The lighted portion of the Moon always points toward the Sun The angle between the Sun and Moon changes as the Moon goes through its phase cycle The angle between the Sun and Moon changes as the Moon goes through its phase cycle Arm exercise on pg 13 of text Arm exercise on pg 13 of text

Eclipses Are caused by shadows cast on objects Are caused by shadows cast on objects Solar Eclipse-Moon blocks light from the Sun and casts a shadow on the Earth Solar Eclipse-Moon blocks light from the Sun and casts a shadow on the Earth Lunar Eclipse-Earth blocks light from the Sun and casts a shadow on the Moon Lunar Eclipse-Earth blocks light from the Sun and casts a shadow on the Moon

Solar Eclipse Moon must be between the Sun and Earth Moon must be between the Sun and Earth Moon must be in what phase for a Solar Eclipse to occur? Moon must be in what phase for a Solar Eclipse to occur? New New Eclipses don’t occur every month due to tilts of both Earth’s and Moon’s orbit Eclipses don’t occur every month due to tilts of both Earth’s and Moon’s orbit

Solar Eclipse Panorama Astronomy Picture of the Day

Lunar Eclipse Earth must be between Sun and Moon Earth must be between Sun and Moon Moon must be in what phase ? Moon must be in what phase ? Full Full More people can see it since Earth’s shadow is larger More people can see it since Earth’s shadow is larger

Lunar Eclipse Montage

Planetary Motions Planet –”wanderer” Planet –”wanderer” Do appear to rise in East and set in West Do appear to rise in East and set in WestBUT…. Don’t follow a consistent motion through the sky compared to the back ground stars Don’t follow a consistent motion through the sky compared to the back ground stars Most times the planets do move Eastward like Sun and Moon (prograde) Most times the planets do move Eastward like Sun and Moon (prograde)

Planetary Motions II But…occasionally these planets appear to move WESTWARD compared to the stars But…occasionally these planets appear to move WESTWARD compared to the stars Retrograde Motion –backward motion Retrograde Motion –backward motion Why does this happen? Why does this happen? We’ll see that soon! We’ll see that soon!

Human Anatomy You have all the tools that ancient astronomers had! You have all the tools that ancient astronomers had! Eyes Eyes Hands Hands Brains Brains Pg. 6 of Text will show you how to put these to use Pg. 6 of Text will show you how to put these to use

Summary You know much already about observational Astronomy You know much already about observational Astronomy Anyone can be an Astronomer Anyone can be an Astronomer Heavenly objects follow predictable motions. Some units of time are defined by these motions Heavenly objects follow predictable motions. Some units of time are defined by these motions Appearance of objects can change for a variety of reasons Appearance of objects can change for a variety of reasons