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Eclipses and Other Phenomena: Transits and Occultations

What is a Transit? What is an Occultation?


  • A transit occurs when a relatively small body passes across the disk of a larger body, usually the Sun or a planet, eclipsing only a very small area (Enclyclopedia Brittanica)
  • Mercury and Venus will transit the sun, although very rarely
  • A useful way to organize the Mercury's transits is by grouping them into series where each member is separated by 16,802 days or 46 years (= sum of 13 and 33 years).  Transits of Venus are much rarer; only six such events have occurred since the invention of the telescope (1631,1639, 1761,1769, 1874 and 1882) 


  • An occultation occurs when an apparently larger body passes in front of an apparently smaller one; usually describes the Moon passing in front of a star 
  • A Total Solar Eclipse is effectively the same event as the Moon occulting the Sun
Additional information from NASA; Encyclopedia Brittanica; Wikipedia

Resources: Transits and Occultations

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