AST-1002 Lecture Notes - Lecture 4: Ecliptic, Orbital Period, Ellipse
Document Summary
The plane of the earth"s orbit around the sun is called the ecliptic. Indeed, all planets - with the exception of. Mercury and pluto - move within 3 deg of the ecliptic. In fact, all constellations of the zodiac also lie along the ecliptic. Viewed from the earth, the ecliptic is also the path traced by the sun through the sky. The earth"s axis is tilted towards the ecliptic by 23. 5 degrees. So the planes of the ecliptic and the celestial equator are also at an angle of 23. 5 degrees to each other in the sky. Mercury"s orbit has a 7-degree tilt relative to the ecliptic, while pluto"s orbit is inclined a full 17 degrees. The orbits of all the planets are ellipses and not circles, as copernicus assumed. However, with the exception of pluto, all orbits are almost circular. Pluto"s orbit is so elliptical that it crosses the one of.
