|Discovered by||Michel Giacobini, Ernst Zinner|
|Discovery date||December 20, 1900|
|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|
|Semi-major axis||3.526 AU|
|Orbital period||6.621 a|
|Earth MOID||0.035 AU (5,200,000 km)|
|Last perihelion||February 11, 2012|
July 2, 2005
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 7-8th 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).
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.
- "JPL Small-Body Database Browser: 21P/Giacobini–Zinner" (last observation:2013-04-01). Jet Propulsion Laboratory. Retrieved 2016-01-10.
- Syuichi Nakano (2012-02-05). "21P/Giacobini-Zinner (NK 2191)". OAA Computing and Minor Planet Sections. Retrieved 2012-02-18.
- King, Bob (29 August 2018). "Comet 21P/Giacobini-Zinner Shines in September - Sky & Telescope". Sky & Telescope. Retrieved 15 September 2018.
- Orbital simulation from JPL (Java) / Horizons Ephemeris
- 21P/Giacobini-Zinner – Seiichi Yoshida @ aerith.net
- 21P at Kronk's Cometography
- Comet 21P - Comet Watch