Eccentricity

Kepler's 1st and 2nd Laws

• Orbits are NOT perfect circles

• Orbits are Elliptical

• One focus point in a planet's orbit is always the sun.

• The second focus point is a mathematically calculated spot in space.​

Kepler's 1st Law

• Eccentricity is the measure of how elliptical an orbit is.

• Always a value between 0-1

  • 0 = ​perfect circle

  • 1 = flat line

​

Calculating Eccentricity Equation:​

Calculating Eccentricity​

You will need a calculator for a few questions in this next section!

Multiple Choice

The path a planet travels around the sun is called its 

• orbit
• ellipse
• barycenter
• precession

Multiple Choice

Planets orbit the Sun in a shape called a(n)

• circle
• ellipse
• focus
• perihelion

Multiple Choice

An ellipse is drawn around two points called

• aphelion
• perihelion
• foci
• axis

Multiple Choice

When a planet orbits the Sun, one of the foci of the elliptical orbit is 

• the axis
• the perihelion
• the center
• the Sun

Multiple Choice

What has an eccentricity of zero

• a straight line
• a large ellipse
• a circle
• a small ellipse

Multiple Choice

Which diagram in the image shows a planet with the LEAST eccentric orbit?

• A

• B

• C

• D

Multiple Choice

Which diagram in the image shows a planet with the MOST eccentric orbit?

• A

• B

• C

• D

Observe the velocity of this planet in orbit. What do you notice?

Some text here about the topic of discussion

States that a planet speeds up as it gets closer to the Sun, and slows down as it moves farther away.

​

• This is due to the gravitational attraction increasing as the planet approaches the sun

  ​

• This causes velocity to also increase.

​

Kepler's Second Law

Multiple Choice

Kepler's 2nd Law deals with 

• the shape of the planets' orbits
• the speed/area the planet travels 
• the length of time it takes the planet to orbit the sun

Multiple Choice

Kepler's second law states that _________.

• a planet moves faster when closer to the Sun

• planets close to the Sun have shorter periods than those farther away

• the Sun is at the center of planetary orbits

• slowly moving planets are close to the Sun

Multiple Choice

Where is the planet moving faster

• Position A to B
• Position B to C
• Position H to I
• Position I to J

Multiple Choice

A planet moves __________ when it is farthest from the sun.

• faster
• slower

Multiple Choice

A planet moves fastest during its orbit around the Sun when...

• it is closest to the sun and gravity has a stronger pull

• it is farthest from the sun and gravity has a stronger pull

• it is closest to the sun and gravity has a weak pull

• it is farthest from the sun and gravity has a weak pull

There is one more law of Planetary Motion!