21P/Giacobini–Zinner

21P/Giacobini–Zinner
Discovery
Discovered by	Michel Giacobini, Ernst Zinner
Discovery date	December 20, 1900
Alternative; 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	6.014 AU
Perihelion	1.038 AU
Semi-major axis	3.526 AU
Eccentricity	0.7056
Orbital period	6.621 a
Inclination	31.8108°
Dimensions	2 km
Last perihelion	February 11, 2012; July 2, 2005
Next perihelion	2018-Sep-10

Comet Giacobini–Zinner (official designation: 21P/Giacobini–Zinner) is a periodic comet in the Solar System.

It was discovered by Michel Giacobini (from Nice, France), who observed the comet in the constellation of Aquarius on December 20, 1900. It was recovered two passages later by Ernst Zinner (from Bamberg, Germany) while observing variable stars near Beta Scuti on October 23, 1913.

During its apparitions, Giacobini–Zinner can reach about the 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). The comet currently has an Earth-MOID of 0.035 AU (5,200,000 km; 3,300,000 mi).^[1]

Giacobini–Zinner was the target of the International Cometary Explorer spacecraft, which passed through its plasma tail on September 11, 1985. In addition, 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 and the project was abandoned.

The comet nucleus is estimated to be 2.0 kilometers in diameter.^[1]

References

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