Planetary Orbits
Planetary orbits in the Solar System refer to the paths that planets follow as they revolve around the Sun. These orbits are generally elliptical, with the Sun located at one of the ellipse’s foci. The gravitational pull of the Sun keeps the planets in motion along these stable, predictable paths. Each planet’s orbital speed and distance from the Sun vary, resulting in different lengths of years for each planet.
Planetary Orbits
Planetary orbits in the Solar System refer to the paths that planets follow as they revolve around the Sun. These orbits are generally elliptical, with the Sun located at one of the ellipse’s foci. The gravitational pull of the Sun keeps the planets in motion along these stable, predictable paths. Each planet’s orbital speed and distance from the Sun vary, resulting in different lengths of years for each planet.
💡 Key Takeaways
- Explain how gravity shapes planetary motion into elliptical orbits with the Sun at a focus.
- Describe why planets speed up near perihelion and slow down near aphelion.
- Apply Kepler's third law to relate a planet's orbital period to the size of its orbit.
- Define key terms like perihelion, aphelion, and eccentricity, and distinguish circular vs elliptical orbits.
❓ Frequently Asked Questions
What is a planetary orbit?
The path a planet follows around a star due to gravity. In a simple two-body model, it’s an ellipse with the star at one focus.
What does Kepler’s First Law state?
Planets move in ellipses around the Sun, not perfect circles; the Sun sits at one focus of the ellipse.
What is an orbital period?
The time it takes for a planet to complete one full orbit around the Sun; longer for orbits farther from the Sun.
What is orbital eccentricity?
A number that describes how stretched an orbit is. e = 0 is a circle; 0 < e < 1 indicates an ellipse.
What are perihelion and aphelion?
Perihelion is the closest point to the Sun; aphelion is the farthest point in a planet’s orbit.