Kepler's Laws of Planetary Motion Flashcards
What is the path around the sun?
An ellipse
What is the shape of the path of each planet around the sun?
An oval shape
What is in the ellipse?
Two foci/points
What determines the shape of the ellipse?
The foci; the farther apart they are, the more elongated the ellipse is
What do ellipses have?
Eccentricity
What is eccentricity?
The measurement of how elongated a closed circle is
How is eccentricity measured?
In values of 0.1 to 1
What is the eccentricity of a perfect circle?
Zero
What is the rule of ellipses?
The greater the value, the more elongated the ellipse is
How is eccentricity calculated?
Eccentricity = Distance between foci divided by length of major axis (E = d / L)
What originally prompted Kepler’s 2nd Law of Planetary Motion?
Kepler noticed that the speed of Mars in its orbit changes in predictable ways
What is perihelion?
The point in a planet’s orbit closest to the sun
What is Earth’s perihelion?
147 million kilometers, and occurs annually on January 3rd
What is aphelion?
The point in a planet’s orbit farthest away from the sun
What is Earth’s aphelion?
152 million kilometers, and occurs annually on July 4th
What is the sun’s imaginary line?
Each planet revolves around an imaginary line so that the sun sweeps over equal areas in each time intervals
What does this imaginary line mean?
Planets must move faster at perihelion and slower at aphelion
Why do planets move faster at perihelion?
The sun’s gravity pulls stronger on the planet when it’s closest to it, causing faster movement
Why do planets move slower at aphelion?
The sun’s gravity decreases as the distance between it and the planet, causing slower movement
What is the rule for orbital period?
The closer a planet is to the sun, the shorter the orbital period
What is an orbital period?
The time it takes for a planet to complete one orbit around the sun in Earth years
What is the orbital period squared?
Orbital period squared = its mean solar distance cubed (T^2 = d^3)
What is the distance of Earth from the sun?
93 million miles/1 astronomical unit
What are astronomical units?
Units used to measure distances in our solar system
