Introducing Astronomy You are here Why our subject
Introducing Astronomy You are here…
Why our subject is different Scale ¡ Lack of true experiments ¡ Fundamental origins ¡
Fundamental units of distance Intrasolar measurements l Astronomical Units (AU) Average distance from the Earth to the Sun ¡ 1. 496 x 108 km (93. 7 million miles) ¡
Fundamental units of distance ¡ Interstellar measurements l Light – years (ly) The distance a photon of light will travel in one calendar year ¡ 9. 46 x 1012 km (6 trillion miles) ¡
Fundamental units of distance ¡ Parsec l l 3. 3 ly Based on the angular measurement of parallax to one arc-second
Lack of True Experiments ¡ Laboratory Simulations l l Due to the great scale of the universe, astronomers must try to re-create observed conditions in a laboratory setting Sometimes very difficult Extreme temperatures ¡ Complete vacuum ¡ Intense radiation ¡
Fundamental Origins ¡ Stardust? l l As we and the Earth we live on are accumulated stardust, studying astronomy gives us insight on the origins of the universe All elements except Hydrogen are created in the cores of stars, released only upon the “death” and explosion of that star
¡ Understanding origins allows us to manipulate the four fundamental forces of the universe l ¡ The Unification Theory Origins of life and complex molecules l Advances in medicine and healthcare
Do you ever just look at them, K? ¡ We see an essentially unchanging sky at night l l Moon, Sun, Planets, “visitors” appear to move against a background of immobile stars Objects seem suspended at an unreachable distance ¡ l Constellations are made from stars at various distances Slow processes are unobvious
Which is largest? Kilometer Astronomical Unit Light-year Parsec 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 10 16 17 18 19 20
Which unit best measures the distances between stars? Light-seconds Light-minutes Light-hours Light-months Light-years 1. 2. 3. 4. 5. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 10 14 15 16 17 18 19 20
The word “planet” means Forever Wanderer Stationary Immobile Indivisible 1. 2. 3. 4. 5. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 10 13 14 15 16 17 18 19 20
Which condition is hard to re-create in laboratory simulations? Extreme temperatures Vacuum of space Intense solar radiation All of these 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 16 17 10 18 19 20
Which is used within the solar system? Kilometer Astronomical Unit Light-year Parsec 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 10 16 17 18 19 20
The term “Stardust” refers to the fact that all heavier elements were formed 1. 2. 3. 4. 1 2 3 4 5 6 7 21 22 23 24 25 26 27 In the cores of other stars In black holes 10 At the edge of the known universe At the moment of the Big Bang 8 9 10 11 12 28 29 30 31 32 13 14 15 16 17 18 19 20
Which unit is used primarily on the Earth? Kilometer Astronomical Unit Light-year Parsec 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 10 16 17 18 19 20
Participant Scores 700 Sid Cooper 700 Drew Griffin 700 Angelique Jackson 700 Melissa James 700 Elissa Keller 700 Jeremy King 700 Kenneth Lewis 700 Kristi Warner 600 Thomas Armstrong 600 Jessika Griffin
The Celestial Sphere ¡ Easy to picture the Earth in the center l Latitude, longitude are “projected” onto the Celestial Sphere
¡ ¡ ¡ The North Celestial Pole is directly above Earth’s North Geographic Pole The South Celestial Pole is directly above Earth’s South Geographic Pole The Celestial Equator is directly above Earth’s Equator
The Ecliptic The apparent path of the Sun through the background stars during a year ¡ Tilted 23. 5º to the CEq because the Earth’s axis is tilted 23. 5º from vertical ¡ l Vertical defined as perpendicular to the Earth’s orbit
There is a season; turn, turn ¡ The tilt of the Earth’s axis also explains seasons l l The pole towards the Sun experiences Summer The pole away from the Sun experiences Winter
Dates to remember ¡ March 21 l l ¡ Vernal Equinox Sun, on the ecliptic, moves from the Southern Hemisphere to the Northern Hemisphere June 21 l l l Summer Solstice Sun, on the ecliptic, reaches its highest point in the Northern Hemisphere 23. 5º N of the Equator (Tropic of Cancer) ¡ Cancer USED TO BE the northernmost Zodiacal Constellation
Dates to remember ¡ September 22 l l ¡ Autumnal Equinox Sun, on the ecliptic, moves from the Northern Hemisphere to the Southern Hemisphere December 22 l l l Winter Solstice Sun, on the ecliptic, reaches its highest point in the Southern Hemisphere 23. 5º S of the Equator (Tropic of Capricorn) ¡ Capricorn USED TO BE the southernmost Zodiacal Constellation
The Celestial Equator (CEq) is always directly above The North Pole of the Earth The South Pole of the Earth The Earth’s equator The Prime Meridian 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 16 17 10 18 19 20
The North Celestial Pole (NCP) is always directly above The magnetic North Pole The geographic North Pole The magnetic South Pole The geographic South 10 Pole 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 16 17 18 19 20
The path the Sun appears to travel through the skies is tilted _____ to the CEq. 104. 7° 5. 6° 98° 23. 5° 1. 2. 3. 4. 10 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 16 17 18 19 20
The Celestial Equator (CEq) is always directly above The North Pole of the Earth The South Pole of the Earth The Earth’s equator The Prime Meridian 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 16 17 10 18 19 20
Seasons on Earth are caused by The tilt of the Earth’s axis Earth’s distance from the Sun Gravity between the Earth and the Moon 10 Gravity between the Earth and the Sun 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 16 17 18 19 20
Participant Scores 0 Participant 1 0 Participant 2 0 Participant 3 0 Participant 4 0 Participant 5
Precession ¡ ¡ The Earth’s rotation and the forces acting on it through the Sun and Moon cause the North Pole to “wobble” A “loop” of this wobble takes some 26, 000 years or so
Precession ¡ The “North Star” is actually whichever star is closest to the NCP ¡ We live in a time with a moderately bright star close to the NCP Thuban, Vega, etc. ¡
Precession of the Equinoxes ¡ ¡ The slowly-rotating NCP causes the dates of Equinoxes, etc. to change Also, the dates of Earth’s aphelion (farthest distance from sun) and perihelion (closest approach to sun) change
“The Immovable Firmament” Star positions are calculated on the Celestial Sphere ¡ “Longitude” is measured as Right Ascension, or the amount of time taken from the Vernal Equinox ¡ “Latitude” is measured as Declination, a positive (above) or negative (below) degree from the Celestial Equator (CEq) ¡
What name is given to the projection of Earth’s latitude and longitude into the skies? The Chrysanthemum Throne The Celestial Sphere The Sky Map The Astronomical Chart 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 16 17 18 19 20 10
What name is given to the point where the Sun crosses the CEq northward? Vernal Equinox Summer Solstice Autumnal Equinox Winter Solstice 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 16 17 18 19 20 10
How much is Earth’s rotational axis tilted to the Ecliptic? 4º 360º 23. 5º 5º 451º 1. 2. 3. 4. 5. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 16 17 18 19 20 10
When is the Sun directly overhead if you are in Montevideo, Uruguay (latitude 23. 5º S)? June 21 September 22 December 22 March 21 1. 2. 3. 4. 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 13 14 15 16 17 18 19 20 10
The Earth’s rotational axis is ALWAYS pointed towards 1 2 3 4 5 6 7 8 9 10 11 12 21 22 23 24 25 26 27 28 29 30 31 32 1. 2. 3. 4. 5. 6. 7. 13 14 15 16 17 18 19 20 The Sun The North Star The North Celestial Pole Away from the Sun 1&3 2&4 10
Participant Scores 0 Participant 1 0 Participant 2 0 Participant 3 0 Participant 4 0 Participant 5
A sample reading Summer Solstice occurs on June 21 ¡ R. A. : 6 hours ¡ Dec. : +23° 22’ N ¡ In the constellation Gemini (moving into Taurus, c. 2150 A. D. ) ¡
A sample reading Betelgeuse (α Orionis) ¡ R. A. : 5 hours, 55’, 10. 3“ ¡ Dec. : +07° 24’ 25”N ¡ In the constellation Orion ¡
“What is a day to Me? ” ¡ A standard day l ¡ 24 hours A sidereal day l l l 23 h 56 m 4 s or so… Time it takes for the Earth to face the same star in space Explains why the amount of daylight changes per day at different latitudes on the Earth
How old are you? ¡ A Mean Solar Year is 365. 256 days long l One complete orbit around the Sun
¡ A Tropical Year is 365. 242 days long l ¡ The time from one Vernal Equinox to the next The difference (about 20 min or so) is the cause of the apparent precession of the poles
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