Giacobini–Zinner
A Jupiter-family comet, parent of the Draconid meteor shower, and the first comet ever visited by a spacecraft — NASA's ICE probe flew through its tail in 1985.
Imagery
21P Giacobini-Zinner orbit
Part of the orbit of the comet 21P/Giacobini-Zinner
Retouched picture by Harlock81 · Public domain
Orbit & physical parameters
Osculating orbit and physical parameters from the NASA JPL Small-Body Database · Jupiter-family Comet · near-Earth · epoch 2017-11-13 (JD 2458070.5 TDB) · Earth MOID 0.017758 au
| Semi-major axis | 3.500303 ± 1.3706e-7 au | NASA JPL · calculated |
| Eccentricity | 0.71047 ± 5.3044e-8 | NASA JPL · calculated |
| Perihelion distance | 1.013441 ± 2.0656e-7 au | NASA JPL · calculated |
| Aphelion distance | 5.987165 ± 2.3444e-7 au | NASA JPL · calculated |
| Inclination | 32.002592 ± 7.1517e-6 deg | NASA JPL · calculated |
| Longitude of ascending node | 195.40448 ± 2.2114e-5 deg | NASA JPL · calculated |
| Argument of perihelion | 172.812482 ± 2.6223e-5 deg | NASA JPL · calculated |
| Orbital period | 2,392 ± 0.00014 d | NASA JPL · calculated |
| Diameter | 2 km | NASA JPL · catalogued |
Full field-level provenance
- Semi-major axis: Jet Propulsion Laboratory / Solar System Dynamics · JPL SBDB · orbit.elements · a · JPL orbit determination (least-squares fit to the observation arc) · calculated · JPL solution by Shantanu Naidu, 1993 obs · retrieved 2026-07-11
- Eccentricity: Jet Propulsion Laboratory / Solar System Dynamics · JPL SBDB · orbit.elements · e · JPL orbit determination (least-squares fit to the observation arc) · calculated · JPL solution by Shantanu Naidu, 1993 obs · retrieved 2026-07-11
- Perihelion distance: Jet Propulsion Laboratory / Solar System Dynamics · JPL SBDB · orbit.elements · q · JPL orbit determination (least-squares fit to the observation arc) · calculated · JPL solution by Shantanu Naidu, 1993 obs · retrieved 2026-07-11
- Aphelion distance: Jet Propulsion Laboratory / Solar System Dynamics · JPL SBDB · orbit.elements · ad · JPL orbit determination (least-squares fit to the observation arc) · calculated · JPL solution by Shantanu Naidu, 1993 obs · retrieved 2026-07-11
- Inclination: Jet Propulsion Laboratory / Solar System Dynamics · JPL SBDB · orbit.elements · i · JPL orbit determination (least-squares fit to the observation arc) · calculated · JPL solution by Shantanu Naidu, 1993 obs · retrieved 2026-07-11
- Longitude of ascending node: Jet Propulsion Laboratory / Solar System Dynamics · JPL SBDB · orbit.elements · om · JPL orbit determination (least-squares fit to the observation arc) · calculated · JPL solution by Shantanu Naidu, 1993 obs · retrieved 2026-07-11
- Argument of perihelion: Jet Propulsion Laboratory / Solar System Dynamics · JPL SBDB · orbit.elements · w · JPL orbit determination (least-squares fit to the observation arc) · calculated · JPL solution by Shantanu Naidu, 1993 obs · retrieved 2026-07-11
- Orbital period: Jet Propulsion Laboratory / Solar System Dynamics · JPL SBDB · orbit.elements · per · JPL orbit determination (least-squares fit to the observation arc) · calculated · JPL solution by Shantanu Naidu, 1993 obs · retrieved 2026-07-11
- Diameter: Jet Propulsion Laboratory / Solar System Dynamics · JPL SBDB · phys_par · phys.diameter · catalogued value · JPL solution by Shantanu Naidu, 1993 obs · retrieved 2026-07-11
Orbital elements are a calculated JPL orbit-determination fit, all referred to the single osculating epoch above (solution by Shantanu Naidu); each carries its own uncertainty. Fields the database did not provide are omitted, never invented.
Classification & origin
Meteor shower: Parent of the Draconid meteor shower.
Knowledge connections
- Member of groupJupiter-Family Comets
- Source reservoirScattered Disc
Sources
The primary and reference sources this topic draws on.
- 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.
- NASA JPLJet Propulsion Laboratory / Solar System Dynamics
Orbital data, ephemerides, and small-body parameters for planets, asteroids, and comets.