What is Orbital Eccentricity?
Orbital eccentricity is a dimensionless parameter that determines the amount by which an orbit around another body deviates from a perfect circle. In celestial mechanics, it is one of the six Keplarian elements used to define the shape and orientation of a celestial body's path through space. A value of 0 indicates a perfectly circular orbit, while values between 0 and 1 represent elliptical orbits.
How to Use This Calculator
To use the Orbital Eccentricity Calculator, you need two primary measurements: the Apoapsis (the farthest point in the orbit from the center of mass) and the Periapsis (the closest point in the orbit). Simply enter these values in consistent units (e.g., kilometers, miles, or Astronomical Units) and click calculate. The tool will provide the eccentricity value and the classification of the orbit.
Understanding the Results
The resulting eccentricity value (e) classifies the shape of the trajectory:
- e = 0: Circular orbit.
- 0 < e < 1: Elliptic orbit (e.g., Earth's orbit around the Sun is approximately 0.0167).
- e = 1: Parabolic trajectory (an escape orbit).
- e > 1: Hyperbolic trajectory (the object will not return to the primary body).
Frequently Asked Questions
What is the formula for eccentricity?
The standard formula used in this calculator is e = (ra - rp) / (ra + rp), where ra is the apoapsis distance and rp is the periapsis distance.
Why is eccentricity important?
Eccentricity affects the climate and seasonal variations of a planet. For example, a high eccentricity would mean a planet experiences extreme temperature changes as it moves significantly closer and farther from its star during its orbital cycle.
Can eccentricity be negative?
No, in standard celestial mechanics, eccentricity is defined as a non-negative value. A value below zero has no physical meaning in this context.