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Download Name: Period: Date: The Celestial Sphere What is the Celestial
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Name: The Celestial Sphere Period: Date: What is the Celestial Sphere? _______________________________________________________________________________ _______________________________________________________________________________ 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 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 __________. 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 We can use the “celestial sphere” idea to help _____________ objects in the sky. 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 • The ____________________ are the two spots ________________ away from the celestial equator. • Summer solstice: _________________ day of the year • Winter solstice: ________________ day of the year The Equinoxes • 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 • 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 _____________________.