Dictionary term
Orbital Eccentricity
Direct answer
Orbital Eccentricity is a dimensionless measure of how much a conic orbit departs from a circle.
It quantifies orbital shape from circular to open trajectories.
It quantifies orbital shape from circular to open trajectories.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.Quick reference
- Use when
- Interpret eccentricity with the conic type and current element epoch.
- Do not use it for
- Eccentricity alone does not give orbit size, orientation, or current position.
- Reference category
- Astronomy & Skywatching
- Related terms
- Orbital Elements, Semimajor Axis, Orbital Inclination, Longitude of Ascending Node
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The story behind Orbital Eccentricity
Ellipse geometry supplied eccentricity before Newton explained orbital gravitation.
Orbital Eccentricity: fact and faith, kept distinct
This is a factual astronomy reference. It can support wonder at the created order without becoming a claim of fate, worship, or private revelation.
Orbital Eccentricity in numerology
Orbital Eccentricity is not a numerology claim. Any numbers attached to it should retain their ordinary scientific, calendrical, navigational, or historical meaning unless a separate symbolic interpretation is clearly labeled.
Why Orbital Eccentricity matters
It distinguishes nearly circular planetary orbits from elongated cometary paths.
Orbital Eccentricity at work: an example
An ellipse has eccentricity between zero and one; a parabola has one.
Where interpretation stops
Orbital Eccentricity is presented as sourced astronomy, calendrical, Earth-science, cultural, or instrument-history reference. Definitions should distinguish measured phenomena from civil convention and historical interpretation, preserve location and time dependencies, and avoid turning factual sky data into a deterministic personal claim.
Sources and editorial method
Research references used for this entry include:
- NASA Science: Orbits and Kepler’s Laws - NASA explanation of orbital ellipses, orbital periods, and Kepler’s laws of planetary motion.
- U.S. Naval Observatory: Astronomical Almanac Glossary - Definitions for astronomical coordinates, time, reference systems, and observable phenomena.
- Source
- The Great Almanac Dictionary
- Category
- Astronomy & Skywatching
- Also appears in
- Astronomy & Skywatching
- Aliases
- None listed
- Last updated
- 2026-07-16
Compare circular and elongated orbits
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Common questions
What is Orbital Eccentricity?
Orbital Eccentricity is a dimensionless measure of how much a conic orbit departs from a circle.
How is Orbital Eccentricity used in an almanac?
Interpret eccentricity with the conic type and current element epoch.
What should I avoid when interpreting Orbital Eccentricity?
Eccentricity alone does not give orbit size, orientation, or current position.
