Download Name: Period: Date: The Celestial Sphere What is the Celestial

Name:
The Celestial Sphere
Period:
Date:
What is the Celestial Sphere?
 _______________________________________________________________________________
_______________________________________________________________________________
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Imagine that there is a giant, spherical projector screen around the earth and all the light from
objects in space is shining onto it to make the patterns we see (like constellations).
Diurnal Motion
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The entire sky appears to rotate once in ________ hours. This is termed the daily or ___________
motion of the celestial sphere, and results from the daily rotation of the earth on its __________.
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The diurnal motion affects all objects in the sky and does not change their positions ___________
to each other.
Some objects also appear to move with respect to the other objects on the celestial sphere. These
are the "wanderers" of the ancient astronomers: the _______________, the __________, and the
_____________. This is due to the Earth’s orbit around the sun.
The Celestial Sphere
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We can use the “celestial sphere” idea to help _____________ objects in the sky.
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The stars rotate around the North and South _______________ Poles. These are the points in the
sky directly above the _______________ north and south poles.

Fortunately, for those in the __________________ hemisphere, there is a fairly bright star very
close to the North Celestial Pole called ______________ (or the North star).

Another important reference marker is the _______________________: an imaginary circle
around the sky directly above the Earth's equator. All the stars rotate in a path that is
________________ to the celestial equator.

Stars that are close to the celestial poles never appear to rise or set. These are called
_______________________ stars.
The “road of the sun” on the Celestial Sphere
1. The sun has a _________________ (daily) motion from east to west due to the earth’s spinning
around its axis, ~ 24 h
2. The sun also changes its ____________________ in the sky ~ 1 degree per day, ~ 365.25 days
What is the ecliptic?
•
The Earth and sun orbit each _____________________________________, called the ecliptic.
•
That means the path of the __________________ across the sky will be on the _______________.
Constellations of the Zodiac
•
Your zodiac “sign” is the ____________________ the sun was in on the ________ you were born.
•
Since the Earth orbits the sun, when standing on Earth and looking up at the sun, there will be a
different _________________ in the background depending ______________________________.
The solstices
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The ____________________ are the two spots ________________ away from the celestial
equator.
•
Summer solstice: _________________ day of the year
•
Winter solstice: ________________ day of the year
The Equinoxes
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The ecliptic and the celestial equator cross in _____________ places.
•
In these two spots, there is an equal amount of ______________ and _______________ (12 hours
each). These are the ___________________.
What causes the seasons?
________________________________________________________________________________, NOT
___________________________________________________________________________________!!!
Tlilt of the Axis
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When the northern hemisphere is tilted ______________ the sun, we receive more direct sunlight.
•
When we are tilted ____________ from the sun, its rays are spread out over a _______________
area so they don’t give us as much _____________________.