Kepler Review for Test

Kepler Review for Test

Who is Kepler?

• Johannes Kepler was an astronomer who discovered the patterns of planetary motion we know today (how the planets move)

• He proposed that planets orbit in ovals NOT circles.

Law 1 : Law of Ellipses

• Planets travel (orbit) in ellipses (ovals)

• Every ellipses has TWO foci (focus point)

• ONE of the two foci is the sun

Law 1 : Law of Ellipses

• Notice how the sun is to the side of the ellipse NOT in the center

• The black "x" is the second foci - it's just a spot in space.

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Law 2 : Law of Equal Areas

• As long as the area is the - the planets will take the same amount of time to travel

• Equal area means equal time

Law 2 : Law of Equal Areas

• The speed of a planet's orbit changes based on how close it is to the sun.

• The position CLOSEST to the sun is called Perihelion. At this position the planet moves FASTEST.

• The position FARTHEST to the sun is called Aphelion. At this position the planet moves SLOWEST.

Law 3 : Law of Harmonies

• The farther away a planet's orbit is from the sun (A.U.) the longer the orbital period

• p² / a³ = about 1

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Multiple Choice

Geocentric means...

• earth centered

• sun centered

• moon centered

Multiple Choice

What is an orbital period?

• how long it takes a planet to make a full trip around the sun

• how long it takes the sun to make a full trip around a planet

• How far away the planet is from the sun

• How far away the sun is from the planet

Multiple Choice

If a planet travels at 50,000 mph at the perihelion, how fast will the planet travel when it is at the aphelion?

• 75,000 mph

• 65,000 mph

• 55,000 mph

• 45,000 mph

Multiple Choice

Where is the sun in comparison to the ellipse?

• in the center

• inside the ellipse

• outside the ellipse

Multiple Choice

Which model of planetary motion is correct?

Multiple Select

Which of these planets have a smaller A.U. from the sun than Earth?

• Mercury

• Venus

• Mars

• Jupiter

• Saturn