The stars and constellations in the sky appear to change positions throughout the night and throughout the year primarily due to the rotation of the Earth on its axis and its orbit around the Sun.
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Rotation of the Earth: As the Earth rotates from west to east, different parts of the sky come into view throughout the night. This rotation causes stars and constellations to appear to move across the sky, changing their position relative to an observer on the ground.
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Orbiting the Sun: Throughout the year, as the Earth moves in its elliptical orbit around the Sun, the night sky changes. Different constellations become visible in different seasons because the Sun's position in the sky blocks our view of certain stars during daylight when we are facing the Sun. As we move through the year, we see new constellations that are in the opposite direction of the Sun.
In summary, the apparent motion of stars and constellations is a result of both the Earth's rotation and its annual orbit around the Sun.