Solar System Models & Kepler's Laws

Question 1

What causes retrograde motion?

Answer 1

Apparent motion caused when one planets moves from being behind another planet to being in front of the other planet.

Question 2

Kepler’s First Law

Answer 2

Semi-major axis is equivalent to the average distance from the Sun

Question 3

Eccentricity

Answer 3

How squashed or “out of round” the ellipse is; a number ranging from 0 for a circle to 1 for a straight line

Question 4

Kepler’s Second Law

Answer 4

A line from a planet to the Sun sweeps over equal areas in equal intervals of time

Question 5

Perihelion

Answer 5

planets move faster when near the Sun

Question 6

Aphelion

Answer 6

planets move slower when they are far from the

Question 7

Kepler’s Third Law

Answer 7

A planet’s orbital period squared is proportional to
the semi-major axis cubed; a^3 = P^2

Question 8

What determines how long it takes for a planet to orbit its star?

Answer 8

The size of the orbit; Planets that orbit near the Sun orbit with
shorter periods than planets that are far from the Sun