introducing astronomy you are here…. why our subject is different scale lack of true experiments...
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Introducing Astronomy
You are here…
Why our subject is different
Scale Lack of true experiments Fundamental origins
Fundamental units of distance
Intrasolar measurements 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 measurementsLight – 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 3.3 ly Based on the angular measurement of
parallax to one arc-second
Lack of True Experiments
Laboratory Simulations 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? 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 The Unification Theory
Origins of life and complex molecules Advances in medicine and healthcare
Do you ever just look at them, K?
We see an essentially unchanging sky at night Moon, Sun, Planets, “visitors” appear to
move against a background of immobile stars
Objects seem suspended at an unreachable distance
Constellations are made from stars at various distances
Slow processes are unobvious
Which is largest?
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1. Kilometer2. Astronomical Unit3. Light-year4. Parsec
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Which unit best measures the distances between stars?
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1. Light-seconds2. Light-minutes3. Light-hours4. Light-months5. Light-years
The word “planet” means
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1. Forever2. Wanderer3. Stationary4. Immobile5. Indivisible
Which condition is hard to re-create in laboratory simulations?
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1. Extreme temperatures2. Vacuum of space3. Intense solar radiation4. All of these
Which is used within the solar system?
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1. Kilometer2. Astronomical Unit3. Light-year4. Parsec
The term “Stardust” refers to the fact that all heavier elements were formed
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1. In the cores of other stars2. In black holes3. At the edge of the known
universe4. At the moment of the Big
Bang
Which unit is used primarily on the Earth?
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1. Kilometer2. Astronomical Unit3. Light-year4. Parsec
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 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 Vertical defined as perpendicular to the
Earth’s orbit
There is a season; turn, turn, turn
The tilt of the Earth’s axis also explains seasons The pole towards the Sun experiences
Summer The pole away from the Sun
experiences Winter
Dates to remember
March 21 Vernal Equinox Sun, on the ecliptic, moves from the
Southern Hemisphere to the Northern Hemisphere
June 21 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 Autumnal Equinox Sun, on the ecliptic, moves from the Northern
Hemisphere to the Southern Hemisphere December 22
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
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1. The North Pole of the Earth
2. The South Pole of the Earth
3. The Earth’s equator4. The Prime Meridian
The North Celestial Pole (NCP) is always directly above
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1. The magnetic North Pole2. The geographic North
Pole3. The magnetic South Pole4. The geographic South
Pole
The path the Sun appears to travel through the skies is tilted _____ to the CEq.
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1. 104.7°
2. 5.6°
3. 98°
4. 23.5°
The Celestial Equator (CEq) is always directly above
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1. The North Pole of the Earth
2. The South Pole of the Earth
3. The Earth’s equator4. The Prime Meridian
Seasons on Earth are caused by
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1. The tilt of the Earth’s axis2. Earth’s distance from the
Sun3. Gravity between the
Earth and the Moon4. Gravity between the
Earth and the Sun
Participant Scores
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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?
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1. The Chrysanthemum Throne
2. The Celestial Sphere3. The Sky Map4. The Astronomical Chart
What name is given to the point where the Sun crosses the CEq northward?
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1. Vernal Equinox2. Summer Solstice3. Autumnal Equinox4. Winter Solstice
How much is Earth’s rotational axis tilted to the Ecliptic?
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1. 4º2. 360º3. 23.5º4. 5º5. 451º
When is the Sun directly overhead if you are in Montevideo, Uruguay (latitude 23.5º S)?
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1. June 212. September 223. December 224. March 21
The Earth’s rotational axis is ALWAYS pointed towards
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1. The Sun2. The North Star3. The North Celestial Pole4. Away from the Sun5. 1 & 36. 2 & 37. 2 & 4
Participant Scores
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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 24 hours
A sidereal day 23h56m4s 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 One complete orbit around the Sun
A Tropical Year is 365.242 days long The time from one Vernal Equinox to
the next
The difference (about 20min or so) is the cause of the apparent precession of the poles