67P/Churyumov–Gerasimenko

67P/Churyumov-Gerasimenko (abbreviated as 67P or 67P/C-G) is a Jupiter family comet that originated from the Kuiper Belt. It has an orbital period 
of 6.45 years, a rotation period of 12.4 hours and a maximum velocity of 135,000 km/h. It was first observed on photographic plates in 1969 by Soviet astronomers Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko, after whom it is named. It most recently came to perihelion (closest approach to the Sun) on 2 November 2021, and will next come to perihelion on 9 April 2028.
Churyumov–Gerasimenko was the destination of the European Space Agency's Rosetta mission, launched on 2 March 2004. Rosetta rendezvoused with Churyumov–Gerasimenko on 6 August 2014 and entered orbit on 10 September 2014. Rosetta's lander, Philae, landed on the comet's surface on 12 November 2014, becoming the first spacecraft to land on a comet nucleus. On 30 September 2016, the Rosetta spacecraft ended its mission by landing on the comet in its Ma'at region.
== Discovery ==
Churyumov–Gerasimenko was discovered in 1969 by Klim Ivanovich Churyumov of the Kyiv University's Astronomical Observatory, who examined a photograph that had been exposed for comet Comas Solà by Svetlana Ivanovna Gerasimenko on 11 September 1969 at the Alma-Ata Astrophysical Institute, near Alma-Ata (now Almaty), the then-capital city of Kazakh Soviet Socialist Republic, Soviet Union. Churyumov found a cometary object near the edge of the plate, but assumed that this was comet Comas Solà.
After returning to his home institute in Kyiv, Churyumov examined all the photographic plates more closely. On 22 October, about a month after the photograph was taken, he discovered that the object could not be Comas Solà, because it was about 1.8 degrees off the expected position. Further scrutiny produced a faint image of Comas Solà at its expected position on the plate, thus proving the other object to be a different body.
== Contact Binary Shape ==
The comet consists of two lobes connected by a narrower neck, with the larger lobe measuring about 4.1 km × 3.3 km × 1.8 km (2.5 mi × 2.1 mi × 1.1 mi) and the smaller one about 2.6 km × 2.3 km × 1.8 km (1.6 mi × 1.4 mi × 1.1 mi). With each orbit the comet loses matter, as gas and dust are evaporated away by the Sun. It is estimated that currently a layer with an average thickness of about 1 ± 0.5 m (3.3 ± 1.6 ft) is lost per orbit. The comet has a mass of approximately 10 billion tonnes.
The two-lobe shape of the comet is the result of a gentle, low-velocity collision of two objects, and is called a contact binary. The "terraces", layers of the interior of the comet that have been exposed by partial stripping of outer layers during its existence, are oriented in different directions in the two lobes, indicating that two objects fused to form Churyumov–Gerasimenko.
== Surface ==
There are 26 distinct regions on Churyumov–Gerasimenko, with each named after an Egyptian deity; regions on the large lobe are named after gods, whereas those on the small lobe are named after goddesses. 19 regions were defined in the northern hemisphere prior to equinox. Later, when the southern hemisphere became illuminated, seven more regions were identified using the same naming convention.
Region	Terrain 	Region 	Terrain 	Region 	Terrain
Ma'at 	Dust covered 	Ash 	Dust covered 	Babi 	Dust covered
Seth 	Pitted and brittle material	Hatmehit	Large-scale depression	Nut 	Large-scale depression
Aten 	Large-scale depression 	Hapi 	Smooth 	Imhotep	Smooth
Anubis	Smooth 	Maftet 	Rock-like 	Bastet 	Rock-like
Serqet	Rock-like 	Hathor 	Rock-like 	Anuket 	Rock-like
Khepry	Rock-like 	Aker 	Rock-like 	Atum 	Rock-like
Apis 	Rock-like 	Khonsu 	Rock-like 	Bes 	Rock-like
Anhur 	Rock-like, rather friable 	Geb 	Rock-like 	Sobek 	Rock-like
Neith 	Rock-like 	Wosret 	Rock-like 	 	
=== Gates ===
Features described as gates, twin prominences on the surface so named for their appearance, were named after deceased members of the Rosetta team.
Name 	Named after
C. Alexander Gate	Claudia Alexander
A. Coradini Gate 	Angioletta Coradini
== Orbit and Rotation ==
Like the other comets of the Jupiter family, Churyumov–Gerasimenko probably originated in the Kuiper belt and was ejected towards the interior of the Solar System, where later encounters with Jupiter successively changed its orbit.
Up to 1840, the comet's perihelion distance was 4 AU (600 million km), too far for the Sun to vaporize the nucleus. In 1840 Jupiter changed the orbit to a perihelion distance of 3 AU (450 million km), and later encounters further decreased that distance to 2.77 AU (414 million km).
In February 1959, a close encounter with Jupiter moved Churyumov–Gerasimenko's perihelion inward to about 1.29 AU (193 million km), where it remains today. In November 2220 the comet will pass about 0.12 AU (18 million km) from Jupiter which will move perihelion inwards to about 0.8 AU (120 million km) from the Sun.
Before Churyumov–Gerasimenko's perihelion passage in 2009, its rotational period was 12.76 hours. During this perihelion passage, it decreased to 12.4 hours, which likely happened because of sublimation-induced torque.
== Temporary Satellite ==
During perihelion, Rosetta caught glimpse of a small, 13 foot piece of debris in orbit around the comet. The piece of debris was nicknamed "Churymoon" by Rosetta scientists.
== Gallery ==
File:Comet 67P on 14 September 2014 NavCam mosaic.jpg
File:Comet on 7 July 2015 NavCam.jpg
File:NavCam Comet 67P animation 20140806 (cropped).gif
File:67P Churyumov-Gerasimenko surface.gif|Recorded by the Philae lander
File:67P-C-G - March 28 2015 (32370930490).jpg
File:Cliffs of Comet 67P.jpg|Cliffs of 67P
File:Comet 67P on 22 August 2014 NavCam.jpg
File:67P Churyumov-Gerasimenko - Rosetta (32755885495).png
Category:Jupiter Family Comet
Category:Comet
Category:Periodic Comet
Category:Cryasteroid
Category:Objects with No Atmosphere
Category:Objects Not in Hydrostatic Equilibrium
Category:Outer Solar System Object
Category:Objects with Natural Satellites
Category:Objects with Transient Atmospheres
Category:Geoasteroid
Category:Named Comets
Category:Numbered Comets
Category:Objects Visited by Spacecraft