Astronomy 1021 Chapter Notes - Chapter 2: Tropical Year, Lunar Phase, Celestial Pole
28 May 2018
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Department
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Astronomy 1021
Chapter 2: Study Notes, Definitions, Questions, etc.
In which direction does the Earth turn around its axis of rotation?
-west to east
In which direction do we perceive the sky turning around us?
-east to west
What is the Celestial Sphere?
-An imaginary sphere of which the observer is the center and on which all-celestial objects are considered
to lie
What are the two points that the celestial sphere seems to turn around on?
- North Celestial Pole and South Celestial Pole
How do we define the horizon for any person at any point on earth?
-Horizon- Point directly over your head and the plane under your feet that touches Earth an where you are
standing
How do the stars seem to rise and set for someone standing at the equator?
- Stars rise straight up in the sky in the east or setting straight down in the west
For someone living at a mid-northern latitude, (like Mt. Pleasant, latitude 43.5 degrees), where would you
find the North Celestial Pole?
- The North Star is up from the horizon exactly at an angle equal to your latitude
So the North Celestial Pole would be at 43.5 degrees
How do starts near the North Celestial Pole turn around the pole; clockwise or counter-clockwise?
Counter-clockwise
Make sure you know the correct reason why we have seasons on the Earth
- We have seasons because the earth is tilted on its rotation axis of 23.5 degrees
What are the four special dates of the year?
1.Summer Solstice
2. Autumnal Equinox
3. Winter Solstice
4. Vernal Equinox
Summer Solstice
June 21 - Sunlight falls more directly on the Northern Hemisphere, which makes it summer there because
the sun follows a longer and higher path through the sky
Autumnal Equinox
September 21 -Sunlight falls equally on both hemispheres, the earth is tipped slightly away from the sun
Winter Solstice
December 21 - sunlight falls less directly on the Northern Hemisphere, which makes it winter because the
sun follows a shorter and lower path through the sky
Vernal Equinox
March 24 - Sunlight falls equally on both hemispheres, also happens in September, earth is slightly tipped
toward the sun
