The comet as seen by the Rosetta spacecraft
|Discovered by||Klim Ivanovych Churyumov
Svetlana Ivanovna Gerasimenko
|1969 R1, 1969 IV, 1969h, 1975 P1, 1976 VII, 1975i, 1982 VIII, 1982f, 1989 VI, 1988i|
|Epoch 2013-Dec-20 (JD 2456646.5)|
|Aphelion||5.6839 AU (850,300,000 km)|
|Perihelion||1.2429 AU (185,940,000 km)|
|3.4634 AU (518,120,000 km)|
|Dimensions||3.5×4 km (2.2×2.5 mi)|
|0.46 m/s (1.5 ft/s) (estimate)|
|Temperature||−90 °C (183 K; −130 °F)|
Comet Churyumov–Gerasimenko, officially designated 67P/Churyumov–Gerasimenko and sometimes shortened to 67P/C-G, is a comet with a current orbital period of 6.45 years and a rotation period of approximately 12.7 hours. The comet will next come to perihelion (closest approach to the Sun) on 13 August 2015. Like all comets, it is named after its discoverers, Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko, who first observed it on photographic plates in 1969.
Churyumov-Gerasimenko is the destination of the European Space Agency's Rosetta mission, launched on 2 March 2004. The Rosetta spacecraft rendezvoused with the comet on 6 August 2014, with plans to enter orbit after approaching to within 30 km (19 mi) five weeks later. On 15 September 2014, ESA announced choosing "Site J" on the "head" of the comet as the landing site of the Philae probe attached to Rosetta. The planned landing date is 11 November 2014.
The comet was discovered in 1969 by Klim Ivanovych Churyumov of the Kiev Astronomical Observatory, who examined a photograph that had been exposed for periodic comet 32P/Comas Solà by Svetlana Ivanovna Gerasimenko on 11 September 1969 at the Alma-Ata Astrophysical Institute, near Almaty, the then-capital city of Kazakhstan. Churyumov found a cometary object near the edge of the plate, but assumed that this was Comas Solà.
After returning to his home institute in Kiev, 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 that the other object was a newly discovered comet.
Comets are regularly nudged from one orbit to another when they encounter Jupiter in close proximity. Before 1959, Churyumov–Gerasimenko's perihelion distance was about 2.7 AU (400,000,000 km). In February 1959, a close encounter with Jupiter moved its perihelion inward to about 1.3 AU (190,000,000 km), where it remains today.
As of August 2014[update], the comet nucleus currently has an apparent magnitude of roughly 20. The comet next comes to perihelion (closest approach to the Sun) on 13 August 2015. From December 2014 until September 2015 the comet will have an elongation less than 45 degrees from the Sun. On 10 February 2015 the comet will come to solar conjunction when it will appear 5 degrees from the Sun and be 3.3 AU (490,000,000 km) from Earth. Even right after perihelion the comet might only brighten to about apparent magnitude 11, and will require a telescope to be seen.
Churyumov–Gerasimenko is the destination of the Rosetta spacecraft mission, launched 2004, which rendezvoused with the comet in 2014 and, if successful, will be the first mission to land a space probe on a comet.
On 25 April 2012 the deepest observations of the comet to date were taken with the 2-metre Faulkes Telescope by N. Howes, G. Sostero and E. Guido whilst the comet was nearest its aphelion point.
On 6 June 2014 water vapor was detected being released from Churyumov-Gerasimenko at a rate of roughly 1 L/s (0.26 USgal/s) when Rosetta was 360,000 km (220,000 mi) from the comet and the comet was 3.9 AU (580,000,000 km) from the Sun.
On 14 July 2014, images taken by Rosetta showed that the comet's nucleus is irregular in shape with two distinct sections. One explanation is that it is a contact binary formed by a collision between two comets, but other formation scenarios exist: for example, it may have been gravitationally affected by another object, or significant amounts of ice may have evaporated from its surface to leave behind an asymmetric shape. The size of the nucleus is estimated as 3.5×4 km (2.2×2.5 mi).
Ground controllers rendezvoused Rosetta with Churyumov–Gerasimenko on 6 August 2014. This was achieved by reducing its relative velocity to 1 m/s (4 km/h; 2 mph). Beginning in May 2014, the velocity of the spacecraft was reduced by 2,800 km/h (780 m/s; 1,700 mph) with a series of thruster firings.
Plans call for Rosetta to enter actual orbit around the comet on September 10, after performing a series of further manoeuvres with thrusters that will bring it to about 30 km (19 mi) from the nucleus.
Descent of a small lander to the comet itself is planned for November 2014. Philae is a 100 kg (220 lb) robotic probe that will set down on the surface with landing gear and "harpoon itself to the surface". The acceleration due to gravity on the surface of the comet has been estimated for simulation purposes at 10−3 m/s2, or about one ten-thousandth of that on Earth.
On 25 August 2014, project managers announced five potential landing sites for Philae. A final site should be selected by mid-September. The European Space Agency announced On Sept. 15, 2014 that the target landing site for the Philae lander is Landing Site J. Touchdown will occur on Nov. 11, 2014. 
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|Wikimedia Commons has media related to Comet Churyumov-Gerasimenko.|
- 67P/Churyumov–Gerasimenko at Cometography.com
- 67P/Churyumov-Gerasimenko at the Wayback Machine (archived 11 November 2007) by the Instituto de Astrofísica de Canarias
- 67P pronunciation guide by the European Space Agency
- "Rosetta's Target: Comet 67P/Churyumov-Gerasimenko" by the European Space Agency
- "Mission to Land on a Comet" by NASA
- 67P multimedia gallery by the European Space Agency
- 67P color image at Astrometrica.at
- 67P size comparison by the European Space Agency
|Periodic comets (by number)|