apparent motions of the celestial objects
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Apparent motions of the Celestial Objects. Do Not Write What is in Yellow . Definitions. Celestial sphere : Imaginary sphere encircling Earth on which all object in the night sky appear Celestial object: Object in the sky outside Earth’s atmosphere; the sun, moon, stars, planets - PowerPoint PPT PresentationTRANSCRIPT
Do Not Write What is in Yellow
APPARENT MOTIONS OF THE CELESTIAL OBJECTS
Definitions
Celestial sphere: Imaginary sphere encircling Earth on which all object in the night sky appear
Celestial object: Object in the sky outside Earth’s atmosphere; the sun, moon, stars, planets
Terrestrial: Objects that are a part of Earth, such as rocks, oceans, and clouds
MotionsThe sun, moon, planets, stars or any distant object
seems to rise in the east and set in the west- this is an illusion: the Earth is the object that is moving
The apparent motion of objects occurs at a rate of 15 degree per hour, which is the rate that earth rotates
Daily Motion: the movement of a celestial object over a 24-hour period
Day: Average interval of time during which the sun passes from its highest point on one day to its highest point on the next; ~24 hours
Zenith: The point on the celestial sphere that is directly above the observer.
From Different PerspectivesMid-Latitudes: Stars appear to move from
east to west in circular pathsNorth Pole: Stars appear to move in a
circle
STAR'S PATH THROUGH THE SKY
The Earth rotates, causing the stars to appear to rise and set. Remember that the Sun is a star. It rotates/spins in place but does not revolve/orbit
InformationSundials were used to tell time using the
apparent movement of the sunThe passing of hours is indicated by the
movement of the shadowDays are short during the winter because
we are pointed away from the sunso the sun is below the horizonmost of the daySundialsMore on sundials
Path of the Planets
Planets do not remain in fixed positions among the stars
Planets change their position from night to night
Each planet has its own unique motion
Sometimes they appear to drift west, other times east
“Planet” = Wanderer
The Moon
The moon revolves around Earth in about 27 days
The moon rises about 50 minutes later each evening
The path of the moon varies from higher to lower depending on the time of year
The moon’s path is similar to the sun’s as it looks like it rises and sets
Apparent Motions of the SunThe sun appears to rise in the east, travel in
an arc across the sky and set in the westThe greater the length of the sun’s path
over an area, the more hours of daylightIn the spring and fall, the sun rises due
(exactly) east and sets due westIn the summer, the sun rises north of east
and sets north of westIn the winter, the sun rises south of east
and sets south of west
Changes in the Altitude of the Sun at Noon
The sun is always highest at local solar noon
Only between the latitudes of 23.5 degrees North and 23.5 degrees South can the noon sun be directly overhead