21P/Giacobini-Zinner

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**21P/Giacobini-Zinner**
Discovery

Discovered by:	Michel Giacobini, Ernst Zinner
Discovery date:	December 20, 1900
Alternate designations:	1900 III; P/1900 Y1; 1913 V; P/1913 U1; 1926 VI; 1933 III; 1940 I; 1946 V; 1959 VIII; 1966 I; 1972 VI; 1979 III; 1985 XIII; 1992 IX
Orbital characteristics ^A
Epoch:	March 6, 2006
Aphelion distance:	6.014 AU
Perihelion distance:	1.038 AU
Semi-major axis:	3.526 AU
Eccentricity:	0.7056
Orbital period:	6.621 a
Inclination:	31.8108°
Last perihelion:	July 2, 2005
Next perihelion:	2012

Comet Giacobini-Zinner is a periodic comet in our solar system, and was discovered by Michel Giacobini (Nice, France) in Aquarius on December 20, 1900.

It was recovered two passages later, by Ernst Zinner (Bamberg, Germany) while observing variable stars near Beta Scuti on October 23, 1913. During its apparitions, the comet can reach about 8th magnitude, but in 1946 it underwent a series of outbursts that made it as bright as 5th magnitude.

It is the parent body of the Giacobinids meteor shower (also known as the Draconids). It was the target of the International Cometary Explorer spacecraft, which passed through its plasma tail on September 11, 1985. Japanese space officials considered redirecting the Sakigake interplanetary probe toward a 1998 encounter with Giacobini-Zinner, but that probe lacked the propellant for the necessary maneuvers.