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Constellations: The Changing Night Sky - Windows to the Universe

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This is a digital image of the scientific illustration known as, Scenographia Systematis Copernicani (the Copernican System) by Andreas Cellarius(1596-1665). Cellarius produced this illustration for his book, Harmonia Macrocosmica; posthumously published in 1660. Look closely to see a Sun-centered image with the Earth’s positions relative to the Sun at the beginning of each season.
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(c)1995 Visual Language, All Rights Reserved

The Changing Night Sky

If you look at the night sky at different times of the year you see different constellations. This change is due to the motion of the Earth in its orbit around the Sun. As the Earth revolves about the Sun, the Sun appears to move through the constellations. Therefore, different constellations will be visible in our night sky at different times of the year. You can't see the stars if the Sun is near them! Each day a few stars are visible in the east that were not visible the night before. If you were to measure how much the sky shifted from one day to the next you would discover that it shifts approximately one degree per day. This should not be surprising because there are 365 days per year and 360 degrees in a circle, like that of the Earth's orbit. The Sun appears to move about one degree in the sky per day as the Earth goes around it, which means the the shift in the stars and constellations we see each night must be about one degree.

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