67P/Churyumov–Gerasimenko

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67P/Churyumov–Gerasimenko
Crop from the 4 August processed image of comet 67P Churyumov Gerasimenko.png
The comet as seen by the Rosetta spacecraft
Discovery
Discovered by Klim Ivanovych Churyumov
Svetlana Ivanovna Gerasimenko
Designations
1969 R1, 1969 IV, 1969h, 1975 P1, 1976 VII, 1975i, 1982 VIII, 1982f, 1989 VI, 1988i[1]
Orbital characteristics[1]
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)
Eccentricity 0.64113
6.45 yr[2]
Inclination 7.0418°
Physical characteristics
Dimensions 3.5×4 km (2.2×2.5 mi)
Mass (1.0±0.1)×1013 kg[3]
Mean density
102±9 kg/m³[4]
Estimated 1 m/s (3 ft/s)[5]
12.4043±0.0007 h[6]
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[1] and a rotation period of approximately 12.4 hours.[6] The comet will next come to perihelion (closest approach to the Sun) on 13 August 2015.[7][8][9] 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.[10][11][12] The Rosetta spacecraft rendezvoused with the comet on 6 August 2014[13][14] and entered orbit on 10 September 2014.[15] Rosetta's lander, Philae, is scheduled to land on the comet's surface on 11 November 2014.[16]

Discovery[edit]

The comet was discovered in 1969 by Klim Ivanovych Churyumov of the Kiev Astronomical Observatory,[17] 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.[18]

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.[18]

Orbital history[edit]

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[19] moved its perihelion inward to about 1.3 AU (190,000,000 km), where it remains today.[9]

After Churyumov-Gerasimenko's 2007 perihelion, observers found that its rotational period had slowed from 12.76 hours to 12.4 hours. It is believed this change resulted due to sublimation-induced torque.[6]

2015 perihelion[edit]

As of August 2014, the comet nucleus currently has an apparent magnitude of roughly 20.[8] The comet next comes to perihelion (closest approach to the Sun) on 13 August 2015.[7] From December 2014 until September 2015 the comet will have an elongation less than 45 degrees from the Sun.[20] 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.[20] Even right after perihelion the comet might only brighten to about apparent magnitude 11,[7] and will require a telescope to be seen.

Rosetta mission[edit]

Very Large Telescope image of 67P/Churyumov–Gerasimenko.[21]

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.

Advance work[edit]

As preparation for the Rosetta mission, Hubble Space Telescope pictures taken on 12 March 2003 were closely analysed. An overall 3D model was constructed and computer-generated images created.[22]

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.[23][24]

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).[12][25][26]

Rendezvous[edit]

Ground controllers rendezvoused Rosetta with Churyumov–Gerasimenko on 6 August 2014.[13][14] 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.[12][27]

Orbit[edit]

Plans call for Rosetta to enter actual orbit around the comet on 10 September, after performing a series of further manoeuvres with thrusters that will bring it to about 30 km (19 mi) from the nucleus.[13][14][28]

Landing[edit]

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".[12] The acceleration due to gravity on the surface of the comet has been estimated for simulation purposes at 10−3 m/s2,[29] or about one ten-thousandth of that on Earth.

On 25 August 2014, project managers announced five potential landing sites for Philae.[30] The final selection, Site J, was announced on 15 September with a target landing date of 11 November.[16] The backup landing location is Site C.[31]

References[edit]

  1. ^ a b c "JPL Small-Body Database Browser: 67P/Churyumov-Gerasimenko". NASA/Jet Propulsion Laboratory. 5 October 2013. Retrieved 21 January 2014. 
  2. ^ "Rosetta's target: Comet 67P/Churyumov-Gerasimenko". European Space Agency. 14 June 2014. Retrieved 22 July 2014. 
  3. ^ Baldwin, Emily (21 August 2014). "Determining the mass of comet 67P/C-G". European Space Agency. Retrieved 21 August 2014. 
  4. ^ Maquet, L.; Colas, F.; Jorda, L.; Crovisier, J. (2012). "67P/Churyumov-Gerasimenko mass determination based on a new method for modeling non-gravitiational forces and accelerations". Asteroids, Comets, Meteors. 16–20 May 2012. Niigata, Japan. Lunar and Planetary Institute. Retrieved 11 December 2013. 
  5. ^ Dambeck, Thorsten (21 January 2014). "Expedition to primeval matter". Max-Planck-Gesellschaft. Retrieved 19 September 2014. 
  6. ^ a b c Mottola, S.; Lowry, S.; Snodgrass, C.; Lamy, P. L.; Toth, I. et al. (September 2014). "The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta". Astronomy and Astrophysics 569. L2. Bibcode:2014A&A...569L...2M. doi:10.1051/0004-6361/201424590. 
  7. ^ a b c Yoshida, Seiichi (30 December 2010). "67P/Churyumov-Gerasimenko". Aerith.net. Retrieved 9 February 2012. 
  8. ^ a b "67P/Churyumov-Gerasimenko". Minor Planet Center. Retrieved 17 June 2014. 
  9. ^ a b Kinoshita, Kazuo (7 May 2009). "67P/Churyumov-Gerasimenko". Comet Orbit. Retrieved 25 April 2009. 
  10. ^ Krolikowska, Malgorzata (2003). "67P/Churyumov–Gerasimenko – potential target for the Rosetta mission". Acta Astronomica 53: 195–209. arXiv:astro-ph/0309130. Bibcode:2003AcA....53..195K. 
  11. ^ Agle, D. C.; Cook, Jia-Rui; Brown, Dwayne; Bauer, Markus (17 January 2014). "Rosetta: To Chase a Comet". NASA. Release 2014-015. Retrieved 18 January 2014. 
  12. ^ a b c d Chang, Kenneth (5 August 2014). "Rosetta Spacecraft Set for Unprecedented Close Study of a Comet". The New York Times. Retrieved 5 August 2014. 
  13. ^ a b c Fischer, D. (6 August 2014). "Rendezvous with a crazy world". The Planetary Society. Archived from the original on 6 August 2014. Retrieved 6 August 2014. 
  14. ^ a b c Bauer, M. (6 August 2014). "Rosetta Arrives at Comet Destination". European Space Agency. Archived from the original on 6 August 2014. Retrieved 6 August 2014. 
  15. ^ Scuka, Daniel (10 September 2014). "Down, down we go to 29 km – or lower?". European Space Agency. Retrieved 20 September 2014. 
  16. ^ a b Fingas, John (15 September 2014). "The Big Picture: Scientists pick a landing site for their historic comet probe". Engadget. Retrieved 20 September 2014. 
  17. ^ "Klim Ivanovich Churyumov". International Astronomical Union. Retrieved 8 August 2014. 
  18. ^ a b Kronk, Gary W. et al. (2010). "67P/1969 R1 (Churyumov-Gerasimenko)". Cometography: A Catalog of Comets; Volume 5: 1960-1982. Cambridge University Press. pp. 241–245. ISBN 052187226X. 
  19. ^ "JPL Close-Approach Data: 67P/Churyumov-Gerasimenko". NASA/Jet Propulsion Laboratory. 29 June 2010. Retrieved 9 February 2012. 
  20. ^ a b "Elements and Ephemeris for 67P/Churyumov-Gerasimenko". Minor Planet Center. Retrieved 9 August 2014. 
  21. ^ "VLT Tracks Rosetta's Comet". European Southern Observatory. 8 September 2014. Retrieved 8 September 2014. 
  22. ^ Buckley, Michael; Villard, Ray; Christensen, Lars (5 September 2003). "Hubble Assists Rosetta Comet Mission". HubbleSite.org. 
  23. ^ Baldwin, Emily (23 June 2014). "First Detection of Water from 67P/C-G". European Space Agency. Retrieved 23 June 2014.  Sungrazer Comets
  24. ^ Agle, D. C.; Brown, Dwayne; Bauer, Markus (30 June 2014). "Rosetta's Comet Target 'Releases' Plentiful Water". NASA. Retrieved 30 June 2014. 
  25. ^ "The twofold comet: Comet 67P/Churyumov-Gerasimenko". Astronomy.com. 17 July 2014. Retrieved 18 July 2014. 
  26. ^ Temming, Maria (17 July 2014). "Rosetta's Comet has a Split Personality". Sky & Telescope. Retrieved 18 July 2014. 
  27. ^ Gannon, Megan (4 August 2014). "Comet-chasing Euro-probe could make history Wednesday". Christian Science Monitor. Retrieved 6 August 2014. 
  28. ^ Lackdawalla, Emily (15 August 2014). "Finding my way around comet Churyumov-Gerasimenko". The Planetary Society. Archived from the original on 15 August 2014. Retrieved 15 August 2014. 
  29. ^ Hilchenbach, M. (2004). "Simulation of the Landing of Rosetta Philae on Comet 67P/Churyumov-Gerasimenko". SIMPACK User Meeting. 9–10 November 2004. Wartburg/Eisenach, Germany. p. 25. Retrieved 6 August 2014. 
  30. ^ Agle, D. C.; Brown, Dwayne; Bauer, Markus (25 August 2014). "Rosetta: Landing site search narrows". NASA. Retrieved 26 August 2014. 
  31. ^ Bauer, Markus (15 September 2014). "'J' Marks the Spot for Rosetta's Lander". European Space Agency. Retrieved 20 September 2014. 

Further reading[edit]

External links[edit]

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