Published:
November 1, 2006
| As Earth orbits the Sun each year, the Sun appears to cross in front of more than a dozen constellations. As observers on a nearly circular path that takes 365 days to complete, we find the Sun moves approximately 1° per day against the background stars. This movement defines a line, called the ecliptic, around the celestial sphere. The ecliptic is inclined 23.5° to the celestial equator because this is the amount Earth's rotation axis is tilted relative to its orbit. |
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