Near-Parabolic Orbit
An orbit with eccentricity very close to 1 — the boundary between bound and unbound. Long-period comets falling in from the Oort cloud on their first passage follow near-parabolic orbits. A near-parabolic orbit signals a distant Solar-System origin, not an interstellar one.
Definition
Eccentricity near 1 — right at the escape boundary; typical of first-time Oort-cloud comets.
The eccentricity ladder
Orbits run from bound and elliptical, through the parabolic boundary, to the strongly hyperbolic trajectories of interstellar objects.
Objects on this trajectory
- C/1999 S4 (LINEAR)Hyperbolic (Solar-System origin)Near-parabolic (e ≈ 1) — a long-period comet
- C/2007 W1 (Boattini)Hyperbolic (Solar-System origin)Near-parabolic (e ≈ 1) — a long-period comet
- C/2017 K2 (PANSTARRS)Hyperbolic (Solar-System origin)Near-parabolic (e ≈ 1) — a dynamically new comet
Sources
The primary and reference sources this topic draws on.
- NASA JPLJet Propulsion Laboratory / Solar System Dynamics
Orbital data, ephemerides, and small-body parameters for planets, asteroids, and comets.
- NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.