ET
Sketch an ellipse and label the major axis, minor
axis, and foci.
Ellipse Anatomy Review
Goal
1. Understand Kepler’s 2nd Law.
2. Begin to explore Kepler’s 3rd Law.
http://astro.unl.edu/naap/pos/animations/kepler.swf
Kepler’s Second Law
Kepler’s Third Law Inquiry Task
1.
2.
3.
4.
Find a partner, grab a computer.
Load www.bacsspacescience.weebly.com.
Open link for Kepler’s Third Law Inquiry Task.
Wait here. We will read through the
introduction as a class.
5. With your partner, work through the 10
exercises listed in the exercises tab.
6. Write your answers, in complete sentences
(use diagrams to help if you like!) in your
notebook.
Kepler’s Third Law – The Math
Planet
P (years)
a (AU)
Mercury
0.241
0.387
Venus
0.615
0.723
Earth
1.000
1.000
Mars
1.881
1.524
Jupiter
11.862
5.203
Saturn
29.458
9.537
P2
a3
Kepler’s Third Law
Planet
P (years)
P2
a (AU)
a3
Mercury
0.241
0.387
0.0581
0.057961
Venus
0.615
0.723
0.3782
0.377933
Earth
1.000
1.000
1
1
Mars
1.881
1.524
3.5382
3.539606
Jupiter
11.862
5.203
140.71
140.8515
Saturn
29.458
9.537
867.77
867.4318
Kepler’s Third Law
P2
0.058
a3
0.058
0.378
0.378
1
1
3.538
3.539
140.71
140.85
867.77
867.43
a 3 = p2
a3 = 1
p2
a 13
p1 2
=
a 23
p2 2
a13 x p22 = a23 x p12
a13
a23
a1
a2
=
3
p12
p22
p
= 1
p2
2
( ) ( )
If Neptune lives at about 30.44 AU from the sun, what would
be its orbit period?
a1
3
= p1
2
(a ) ( p )
2
2
An asteroid orbits the sun with a mean orbital radius of 3.65 X
1011 m. One AU = 1.4957 x 1011 m. Calculate the period of
the asteroid.
a1
3
= p1
2
(a ) ( p )
2
2
The moon Io revolves around Jupiter in 0.0048 sidereal
years. Io has an mean orbital radius of 0.0028 Au’s. If
Europa (another one of Jupiter’s moons) has a period of
rotation of 0.0097 sidereal years, then how far away is
Europa from the center of Jupiter?
a1
3
= p1
2
(a ) (p )
2
2
HW
1. Vocab
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–
–
–
–
Kepler’s Second Law
Kepler’s Third Law
Eccentricity
Period
Semi-major axis
*Don’t forget to observe the moon!