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.[1]

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.[2][3] 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,[4] and by Chinese astronomers.[5]

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.[3]

  • 19 September 1702 – Jupiter occults Neptune
  • 20 July 1705 – Mercury transits Jupiter
  • 14 July 1708 – Mercury occults Uranus
A simulation of Venus transiting Jupiter, as it did on January 3, 1818.
  • 4 October 1708 – Mercury transits Jupiter
  • 28 May 1737 – Venus occults Mercury
  • 29 August 1771 – Venus transits Saturn
  • 21 July 1793 – Mercury occults Uranus
  • 9 December 1808 – Mercury transits Saturn
  • 3 January 1818 – Venus transits Jupiter
  • 22 November 2065 – Venus transits Jupiter
  • 15 July 2067 – Mercury occults Neptune
  • 11 August 2079 – Mercury occults Mars
  • 27 October 2088 – Mercury transits Jupiter
  • 7 April 2094 – Mercury transits Jupiter
  • 21 August 2104 – Venus occults Neptune
  • 14 September 2123 – Venus transits Jupiter
  • 29 July 2126 – Mercury occults Mars
  • 3 December 2133 – Venus occults Mercury

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.[1] 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.

Day Time (UT) Foreground planet Background object Elongation
9 December 1802 07:36 Mercury Acrab 16.2° West
9 December 1808 20:34 Mercury Saturn 20.3° West
22 December 1810 06:32 Venus Xi-2 Sagittarii 11.1° East
3 January 1818 21:52 Venus Jupiter 16.5° West
11 July 1825 09:10 Venus Delta-1 Tauri 44.4° West
11 July 1837 12:50 Mercury Eta Geminorum 17.8° West
9 May 1841 19:35 Venus 17 Tauri 9.2° East
27 September 1843 18:00 Venus Eta Virginis 3.2° West
16 December 1850 11:28 Mercury Lambda Sagittarii 10.2° East
22 May 1855 05:04 Venus Epsilon Geminorum 37.4° East
30 June 1857 00:25 Saturn Delta Geminorum 8.4° East
5 December 1865 14:20 Mercury Lambda Sagittarii 21.0° East
28 February 1876 05:13 Jupiter Acrab 97.6° West
7 June 1881 20:54 Mercury Epsilon Geminorum 21.2° East
9 December 1906 17:40 Venus Acrab 14.9° West
27 July 1910 02:53 Venus Eta Geminorum 31.0° West
24 December 1937 18:38 Mercury Omicron Sagittarii 11.6° East
10 June 1940 02:21 Mercury Epsilon Geminorum 20.1° East
25 October 1947 01:45 Venus Zuben-el-genubi (Alpha-2 Librae) 13.5° East
7 July 1959 14:30 Venus Regulus 44.5° East
27 September 1965 15:30 Mercury Eta Virginis 2.6° West
13 May 1971 20:00 Jupiter Beta Scorpii (both components) 169.5° West
8 April 1976 01:00 Mars Epsilon Geminorum 81.3° East
17 November 1981 15:27 Venus Nunki 47.0° East
19 November 1984 01:32 Venus Lambda Sagittarii 39.2° East
3 July 1989 Saturn 28 Sagittarii
4 December 2015 16:14 Mercury Theta Ophiuchi 9.6° East
17 February 2035 15:19 Venus Pi Sagittarii 42.1° West
1 October 2044 22:00 Venus Regulus 38.9° West
23 February 2046 19:24 Venus Rho-1 Sagittarii 45.4° West
10 November 2052 07:20 Mercury Zuben-el-genubi (Alpha-2 Librae) 2.8° West
22 November 2065 12:45 Venus Jupiter 7.9° West
15 July 2067 11:56 Mercury Neptune 18.4° West
11 August 2069 20:25 Venus Zavijava 38.4° East
3 October 2078 22:00 Mars Theta Ophiuchi 71.4° East
11 August 2079 01:30 Mercury Mars 11.3° West
27 October 2088 13:43 Mercury Jupiter 4.7° West
7 April 2094 10:48 Mercury Jupiter 1.8° West

References
  1. P. Kenneth Seidelmann (ed.), Explanatory Supplement to the Astronomical Almanac: A Revision to the Explanatory Supplement to the Astronomical Ephemeris and the American Ephemeris and Nautical Almanac (Sausalito [CA]: University Science Books, 1992).
  2. Curtis, Jan. "Planet-on-Planet Occultations (Worldwide)". Retrieved 2012-08-08.
  3. Albers, Steven (March 1979). "Mutual Occultations of Planets: 1557-2230". Sky and Telescope. 57 (3): 220. Bibcode:1979S&T....57..220A.
  4. Stubbs, William (1879). Volume 1 of the Historical Works of Gervase of Canterbury. Longman & Company. p. 221.
  5. Hilton, J. L.; Seidelmann, P. K.; Liu, C. (October 1988). "Analysis of ancient Chinese records of occultations between planets and stars" (PDF). Astronomical Journal. 96: 1485. Bibcode:1988AJ.....96.1482H. doi:10.1086/114900.
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