1. Orbits and Kepler’s Laws

2. To stay in orbit…
By stay in orbit, you are being pulled down by gravity and you have to miss the planet you are orbiting around
Must maintain the speed, v where
𝑣= 𝐺𝑀 𝑟

3. Kepler’s First Law
Each planet/object moves around the sun in an orbit which is an ellipse. The sun is at one of the two foci of the ellipse
Also known as the law of ellipses
A circle is a special type of ellipse where the two foci are in the same spot
A parabola is just a part of an ellipse

5. Kepler’s Second Law
2) The straight line joining a planet and the sun sweeps out equal areas in space in equal intervals of time

6. Kepler’s Second Law
As the object get’s closer to a foci, it’ll move faster

7. Kepler’s Third Law
The cube (x3) of the average radius (r) of a planet’s orbit is directly proportional to the square of the period (T) of the planet’s orbit
𝑟 3 ∝ 𝑇 2
𝑟 3 = 𝐶 𝑠 𝑇 2
Cs- Constant of Proportionality (m3/s2)

8. Derive Cs from speed and orbital speed
𝐶 𝑠 = 𝐺𝑀 4 𝜋 2

9. The Search For Exoplanets
We look for a dim spot passing across a star (equivalent to a fly moving across a spot light)
If we know the time it takes to complete one orbit and the approximate mass of the star then…
We can find out the average distance of the orbit