Note:
- Lab is in the Computer Lab this week – turn right after you come in the main
doors, turn left at the end of the hall. It’s room 1220.
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A Planet’s Orbit:
Perihelion – closest point to the sun
Aphelion – furthest point from the sun
-Distance from perihelion to aphelion = major axis = 2a
- Semi-major axis = half of the major axis (a)
- Remember Kepler’s 3rd law:
32
aP
- P is the period in years, a is the semi-major axis in astronomical units (A.U.)
- Label the major axis, the semi major axis on the drawing above.
- Note that the sun is actually a lot closer to the center of the ellipse than shown,
and that the Earth’s orbit is not that elliptical.
