 Comet Giacobini–Zinner photographed fromMoscow, Russia on 9 September 2018. | |
| Discovery | |
|---|---|
| Discovered by | Michel Giacobini Ernst Zinner |
| Discovery date | 20 December 1900 23 October 1913 |
| Designations | |
| P/1900 Y1 P/1913 U1 | |
| 1900 III; 1913 V; 1926 VI; 1933 III; 1940 I; 1946 V; 1959 VIII; 1966 I; 1972 VI; 1979 III; 1985 XIII; 1992 IX | |
| Orbital characteristics[3] | |
| Epoch | 13 November 2017 (JD 2458070.5) |
| Observation arc | 4,922 days (13.48 years) |
| Number of observations | 1,993 |
| Aphelion | 5.987 AU |
| Perihelion | 1.013 AU/2192480km (2031 aparition) |
| Semi-major axis | 3.492 AU |
| Eccentricity | 0.71047 |
| Orbital period | 6.549 years |
| Inclination | 32.002° |
| 195.40° | |
| Argument of periapsis | 172.81° |
| Last perihelion | 25 March 2025[1] |
| Next perihelion | 30 August 2031[2] |
| TJupiter | 2.465 |
| EarthMOID | 0.018 AU |
| JupiterMOID | 0.248 AU |
| Physical characteristics[3][4] | |
| Dimensions | 2.0 km (1.2 mi) |
| 7.39±0.01 hours | |
| Comet total magnitude (M1) | 13.2 |
Comet Giacobini–Zinner (officially designated as21P/Giacobini–Zinner) is aperiodic comet in the Solar System. It was discovered byMichel Giacobini, who observed it in theconstellation ofAquarius on 20 December 1900. It was recovered two orbits later byErnst Zinner, while he was observingvariable stars nearBeta Scuti on 23 October 1913.
Thecomet nucleus is estimated to be 2.0 km (1.2 mi) in diameter.[3] During its apparitions, Giacobini–Zinner can reach about the 7-8thmagnitude,[5] but in 1946 it underwent a series of outbursts that made it as bright as 5th magnitude. It is the parent body of theGiacobinidsmeteor shower (also known as theDraconids). The comet currently has aminimum orbit intersection distance to Earth of 0.035 AU (5.2 million km).[3]
During the apparition of 2018, the optical spectra have revealed the comet is depleted in carbon-chain molecules andcarbon dioxide, likely indicating its origin in relatively warm portion of theSolar System.[6]
Giacobini–Zinner was the target of theInternational Cometary Explorer spacecraft, which passed through its plasma tail at a distance of 7,800 km (4,800 mi) on 11 September 1985, becoming the first comet ever visited in space exploration.[7] Earlier in the same month the comet was observed by thePioneer Venus Orbiter.[8] In addition,Japanese space officials considered redirecting theSakigake interplanetary probe toward a 1998 encounter with Giacobini–Zinner, but that probe lacked the propellant for the necessary maneuvers and the project was abandoned.
21P/Giacobini-Zinner most recently passed perihelion on 25 March 2025, making its closest approach to Earth 4 days before, on 21 March. It brightened to magnitude ~11.[9]
This article incorporates text from this source, which is in thepublic domain.| Numbered comets | ||
|---|---|---|
| Previous 20D/Westphal | 21P/Giacobini–Zinner | Next 22P/Kopff |
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