29

Circular
Orbits:

Limiting case of an ellipse.

Limiting case of an ellipse.

Centripetal acceleration (v2/r) caused by Gravity

Period found by

Keplers 3rd Law just comes from this

Given *P* and *a* (and *G*) this gives us a way to find the mass of a planet or
star

From our text: Horizons, by Seeds