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 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 will be on 22 November 2065 at about 12:43 UTC, when Venus near superior conjunction will transit in front of Jupiter ; 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.
transiting Jupiter, as it did on January 3, 1818.
Twice during the orbital cycles of Jupiter and Saturn, the equatorial 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 may be eclipsed, occulted, or may transit Jupiter's disk.

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.
DayTime Foreground planetBackground objectElongation
9 December 180207:36MercuryAcrab16.2° West
9 December 180820:34MercurySaturn20.3° West
22 December 181006:32VenusXi-2 Sagittarii11.1° East
3 January 181821:52VenusJupiter16.5° West
11 July 182509:10VenusDelta-1 Tauri44.4° West
11 July 183712:50MercuryEta Geminorum17.8° West
9 May 184119:35Venus17 Tauri9.2° East
27 September 184318:00VenusEta Virginis3.2° West
16 December 185011:28MercuryLambda Sagittarii10.2° East
22 May 185505:04VenusEpsilon Geminorum37.4° East
30 June 185700:25SaturnDelta Geminorum8.4° East
5 December 186514:20MercuryLambda Sagittarii21.0° East
28 February 187605:13JupiterAcrab97.6° West
7 June 188120:54MercuryEpsilon Geminorum21.2° East
9 December 190617:40VenusAcrab14.9° West
27 July 191002:53VenusEta Geminorum31.0° West
24 December 193718:38MercuryOmicron Sagittarii11.6° East
10 June 194002:21MercuryEpsilon Geminorum20.1° East
25 October 194701:45VenusZuben-el-genubi 13.5° East
7 July 195914:30VenusRegulus44.5° East
27 September 196515:30MercuryEta Virginis2.6° West
13 May 197120:00JupiterBeta Scorpii 169.5° West
8 April 197601:00MarsEpsilon Geminorum81.3° East
17 November 198115:27VenusNunki47.0° East
19 November 198401:32VenusLambda Sagittarii39.2° East
4 December 201516:14MercuryTheta Ophiuchi9.6° East
17 February 203515:19VenusPi Sagittarii42.1° West
1 October 204422:00VenusRegulus38.9° West
23 February 204619:24VenusRho-1 Sagittarii45.4° West
10 November 205207:20MercuryZuben-el-genubi 2.8° West
22 November 206512:45VenusJupiter7.9° West
15 July 206711:56MercuryNeptune18.4° West
11 August 206920:25VenusZavijava38.4° East
3 October 207822:00MarsTheta Ophiuchi71.4° East
11 August 207901:30MercuryMars11.3° West
27 October 208813:43MercuryJupiter4.7° West
7 April 209410:48MercuryJupiter1.8° West