Planetary transits and occultations
The word "transit" refers to cases where the nearer object appears smaller than the more distant object. Cases where the nearer object appears larger and completely hides the more distant object are known as "occultations". In astronomy, planetary transits and occultations occur when a planet passes in front of another object, as seen by an observer. The occulted object may be a distant star, but in rare cases it may be another planet, in which case the event is called a "mutual planetary occultation" or "mutual planetary transit", depending on the relative apparent diameters of the  objects. Mutual planetary occultations and transits. Mutual occultations or transits of planets are extremely rare. The most recent event occurred on 3 January 1818, and the next will occur on 22 November 2065. Both involve the same two planets: Venus and Jupiter. Historical observations. An occultation of Mars by Venus on 13 October 1590 was observed by the German astronomer Michael Maestlin at Heidelberg. The 1737 event (see list below) was observed by John Bevis at Greenwich Observatory – it is the only detailed account of a mutual planetary occultation. A transit of Mars across Jupiter on 12 September 1170 was  observed by the monk Gervase at Canterbury, and by Chinese astronomers. Future events. The next time a mutual planetary transit or occultation will happen (as seen from Earth) will be on 22 November 2065 at about 12:43 UTC, when Venus near superior conjunction (with an angular diameter of 10.6") will transit in front of Jupiter (with an angular diameter of 30.9"); however, this will take place only 8° west of the Sun, and will therefore not be visible to the unaided/unprotected eye. Before transiting Jupiter, Venus will occult Jupiter's moon Ganymede at around 11:24 UTC as seen  from some southernmost parts of Earth. Parallax will cause actual observed times to vary by a few minutes, depending on the precise location of the observer. List of mutual planetary occultations and transits. There are only 18 mutual planetary transits and occultations as seen from Earth between 1700 and 2200. There is a very long break of events between 1818 and 2065. Mutual occultations, transits, and eclipses of the moons of Jupiter and Saturn. Twice during the orbital cycles of Jupiter and Saturn, the equatorial (and satellite) planes of those planets are aligned with Earth's orbital plane, resulting in  a series of mutual occultations and eclipses between the moons of these giant planets. The terms "eclipse", "occultation", and "transit" are also used to describe these events. A satellite of Jupiter (for example) may be eclipsed (i.e. made dimmer because it moves into Jupiter's shadow), occulted (i.e. hidden from view because Jupiter lies on our line of sight), or may transit (i.e. pass in front of) Jupiter's disk (see also Solar eclipses on Jupiter). Other planetary occultations. This table is another compilation of occultations and transits of bright stars and planets by solar planets. These events are not  visible everywhere the occulting body and the occulted body are above the skyline. Some events are barely visible, because they take place in close proximity to the Sun.