Comet Swift–Tuttle

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Comet Swift–Tuttle (109P/Swift–Tuttle) is a periodic comet with an orbital period of 133 years. It fits the classical definition of a Halley-type comet with a period between 20 and 200 years.[1] It was independently discovered by Lewis Swift and Horace Parnell Tuttle in July 1862. It has a well-known orbit and has a comet nucleus 26 km in diameter.[1]

Chinese records show that in 188 AD the comet reached apparent magnitude 0.1.[2] In 1862, the comet was as bright as Polaris.[3] The comet made a return appearance in 1992, and became visible with binoculars.[4] In 2126 it will be a bright naked-eye comet reaching about apparent magnitude 0.7.[2]

It is the parent body of the Perseid meteor shower, perhaps the best known shower and among the most reliable in performance.[5]

Near-Earth orbit[change | change source]

A close encounter with Earth is predicted for the comet's return to the inner Solar System in the year 4479, around Sept. 15; the closest approach is estimated to be 0.03–0.05 AU, with a probability of impact of 1×10−6, or 0.0001%.[6]

Comet Swift–Tuttle has been described as "the single most dangerous object known to humanity".[7]. However, the probability of Earth impact per orbit is about a million to one against. It is estimated as 2×10−8 (0.000002%).[6] It is the largest Solar System object that makes repeated close approaches to Earth with a relative velocity of 60 km/s.[8][7]

An unusual aspect of its orbit is that it is captured into a 1:11 orbital resonance with Jupiter; it completes one orbit for every 11 of Jupiter.[6]

References[change | change source]

  1. 1.0 1.1 "JPL Small-Body Database Browser: 109P/Swift–Tuttle" (last observation: 1995-03-29). Jet Propulsion Laboratory. Retrieved 2011-05-09. 
  2. 2.0 2.1 Yau, K.; Yeomans, D.; Weissman, P. (1994). "The past and future motion of Comet P/Swift-Tuttle". Monthly Notices of the Royal Astronomical Society 266: 305–316. doi:10.1093/mnras/266.2.305.
  3. David Levy's guide to observing meteor showers (pg12)
  4. Britt, Robert (2005). "Top 10 Perseid Meteor Shower Facts". Retrieved 2009-08-10. 
  5. Bedient, John. "AMS Meteor Showers page", American Meteor Society, 20 June 2010. Retrieved 2010-7-31.
  6. 6.0 6.1 6.2 Chambers J.E. 1995. "The long-term dynamical evolution of Comet Swift–Tuttle". Icarus 114 (2): 372–386. doi:10.1006/icar.1995.1069.
  7. 7.0 7.1 Verschuur, Gerrit L. (1997). Impact!: the threat of comets and asteroids. Oxford University Press. pp. 256 (see p. 116). ISBN 978-0-19-511919-0. 
  8. Weissman, Paul R. (2007). "The cometary impactor flux at the Earth". In Milani, A.; Valsecchi, G.B.; Vokrouhlicky, D. Near Earth objects, our celestial neighbors: opportunity and risk. Proceedings of the International Astronomical Union. 2. Cambridge University Press. pp. 441–450. doi:10.1017/S1743921307003559. Archived from the original on 2009-08-15. Retrieved 2009-08-13.