Elliptical Orbits

Definition

Elliptical orbits refer to the paths traced by objects in space, such as planets, moons, and satellites, around a central body under the influence of gravity. These orbits take the shape of an ellipse, a closed curve with two focal points, rather than a perfect circle.

5 Must Know Facts For Your Next Test

1. Elliptical orbits are described by Kepler's first law, which states that the orbit of every planet is an ellipse with the Sun at one of the two focal points.
2. The eccentricity of an elliptical orbit determines the degree of elongation, with a value of 0 indicating a perfect circle and a value close to 1 indicating a highly elongated ellipse.
3. The semi-major axis of an elliptical orbit determines the size of the orbit, while the eccentricity determines the shape.
4. Satellites in elliptical orbits can have different velocities at different points in their orbit, with the highest velocity at perigee and the lowest velocity at apogee.
5. Elliptical orbits are commonly used for communication, navigation, and scientific satellites, as they can provide coverage over a larger area compared to circular orbits.

Review Questions

• Explain the relationship between the eccentricity and the shape of an elliptical orbit.
  • The eccentricity of an elliptical orbit is a measure of how elongated the orbit is, with a value between 0 and 1. An eccentricity of 0 indicates a perfect circle, while a value closer to 1 indicates a highly elongated ellipse. The eccentricity directly affects the shape of the orbit, with higher eccentricity resulting in a more oval-like shape and lower eccentricity resulting in a more circular shape.
• Describe how the velocity of an object in an elliptical orbit varies throughout its path.
  • Objects in elliptical orbits experience changes in velocity as they move through their orbit. At the point of perigee, where the object is closest to the central body, the velocity is highest. Conversely, at the point of apogee, where the object is farthest from the central body, the velocity is lowest. This variation in velocity is due to the conservation of angular momentum, as the object must move faster when it is closer to the central body to maintain its elliptical orbit.
• Analyze how the characteristics of elliptical orbits, such as eccentricity and semi-major axis, are related to Kepler's laws of planetary motion.
  • Kepler's laws of planetary motion describe the relationships between the properties of elliptical orbits and the motion of objects within those orbits. Specifically, Kepler's first law states that the orbit of every planet is an ellipse with the Sun at one of the two focal points. The eccentricity of the ellipse determines the degree of elongation, while the semi-major axis determines the size of the orbit. Kepler's second and third laws further describe the relationship between the orbital period and the semi-major axis, as well as the equal sweeping of areas by the imaginary line connecting the planet and the Sun. Understanding these connections between the characteristics of elliptical orbits and Kepler's laws is crucial for analyzing the motion of objects in space.

Related terms

Eccentricity:

A measure of the deviation of an elliptical orbit from a perfect circle, with a value between 0 and 1 indicating the degree of elongation.

Apogee and Perigee: The points in an elliptical orbit where the object is farthest (apogee) and closest (perigee) to the central body.

Kepler's Laws of Planetary Motion: A set of three laws that describe the motion of planets in elliptical orbits around the Sun, including the relationship between the orbital period and the semi-major axis.