Astronomy Lab

Kepler’s 3rd Law: P2 = a3   Kepler’s 3rd law is a mathematical formula. It means that if you know the period of a planet’s orbit (P = how long it takes the planet to go around the Sun), then you can determine that planet’s distance from the Sun (a = the semimajor axis of the planet’s orbit).

It also tells us that planets that are far away from the Sun have longer periods than those close to the Sun. They move more slowly around the Sun.

Check out the table of orbital data for the planets. You will notice that the orbital period (P) of the planets gets longer as you go from Mercury to Pluto. Enter the “period” and “Average Distance” in two columns of the Google Spreadsheet and plot. You will get a plot shown in the following Figure. Take a screen shot of the image and upload for this assignment.

 

Planet Period

(yr) Average

Distance (au)

Mercury 0.241 0.39

Venus .615 0.72

Earth 1.00 1.00

Mars 1.88 1.52

Jupiter 11.8 5.20

Saturn 29.5 9.54

Uranus 84.0 19.18

Neptune 165 30.06

Pluto 248 39.44