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Comet 40P/Väisälä from the Vega Observatory.
Discovered by Yrjö Väisälä[1]
Discovery date 08 February 1939[1]
1939 IV, 1949 V, 1960 IV,
1971 VII, 1982 V, 1993 VIII
Orbital characteristics A
Epoch August 23, 2004
Aphelion 7.9890 AU[2]
Perihelion 1.7960 AU[2]
Semi-major axis 4.8925 AU[2]
Eccentricity 0.63291[2]
Orbital period 10.58 a[1]
Inclination 11.539°[2]
Last perihelion 22 January 2004[3]
Next perihelion 15 November 2014[3]
12 November 2025[4]

40P/Väisälä is a periodic comet that was discovered on February 8, 1939. Its orbit was determined on April 26, 1939.[3] In 1994, the diameter of its nucleus was found to be 4.2 km, similar in size to that of Comet Encke.[2]


Comet Väisälä was discovered accidentally on photographs exposed for minor planets. Originally, it was given the asteroid designation 1939 CB.[1][2] However, additional findings revealed that the object was of cometary nature. The visual magnitude of Väisälä at the time of its discovery was 15. The orbital characteristics of the new comet at the time of its discovery were "a period of about 10 years, a perihelion date of 1939 April 26.0, and a perihelion distance of 1.75 AU."[1]

Close Approaches

File:Orbit of Vaisala.gif
Orbit of 40P/Väisälä, which crosses the orbit of Jupiter and is frequently gravitationally perturbed

The orbit of Comet Väisälä resembles that of many centaurs, and is therefore unstable[5] over thousands of years due to gravitational interactions with the gas giant Jupiter. One such close approach, 0.41 AU in December 31, 1961, increased its perihelion distance from 1.74 AU to 1.87 AU and increased its orbital period from 10.46 to 11.28 years. On September 21, 1973, an approach of Jupiter 1 AU away decreased perihelion distance from 1.87 AU to 1.80 AU decreased orbital period from 11.28 to 10.88 years.[1] Väisälä will make one more close approach in the 21st century,[2] but it will have a minimal effect.[1] However, in the year 2127, the comet will make a close approach of only 0.096 AU from Jupiter,[2] and reduce perihelion to 1.4 AU.


  1. ^ a b c d e f g Gary W. Kronk. "40P/Vaisala 1". Cometography. Retrieved 3 November 2013. 
  2. ^ a b c d e f g h i "40P/Vaisala 1 orbit diagram". JPL Small-Body Database. Jet Propulsion Laboratory. SPK-ID: 1000101. 
  3. ^ a b c Yoshida, Seiichi (2006). "40P/Vaisala 1". Aerith. Retrieved 3 November 2013. 
  4. ^ "40P/Vaisala Orbit". Minor Planet Center. Retrieved 2014-10-29. 
  5. ^ Horner, J.; Evans, N.W.; Bailey, M. E. (2004). "Simulations of the Population of Centaurs I: The Bulk Statistics". Monthly Notices of the Royal Astronomical Society 354 (3): 798–810. Bibcode:2004MNRAS.354..798H. arXiv:astro-ph/0407400. doi:10.1111/j.1365-2966.2004.08240.x. 

External links

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Periodic comets (by number)
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