http://SaturnianCosmology.Org/ mirrored file For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== Eclipse Banner Blue Bar Transits of Venus Six Millennium Catalog: 2000 BCE to 4000 CE Fred Espenak Blue Bar A transit is the passage of a planet across the Sun's bright disk. At this time, the planet can be seen as a small black disk slowly moving in front of the Sun. The orbits of Mercury and Venus lie inside Earth's orbit, so they are the only planets which can pass between Earth and Sun to produce a transit. Transits are very rare astronomical events. In the case of Venus, there are on average two transits every one and a quarter centuries. A transit of Venus occurs only if the planet is in inferior conjunction with the Sun (between Earth and Sun) and is also crossing the through Earth's orbital plane (the Ecliptic). During the present period in Earth's history, Venus's orbit crosses Earth's orbital plane in early June and early December each year. If the Venus is passing between the Earth and Sun at that time, a transit will be seen. During the six millennium period 2000 BCE to 4000 CE^1 , Earth experiences 81 transits of Venus across the Sun. These events can be organized into two groups: All Transits = 81 = 100.0% June (Descending Node^2 ) = 44 = 54.3 % December (Ascending Node^3 ) = 37 = 45.7 % When a transit of Venus occurs, a second one often follows eight years later. This is because the orbital periods of Venus (224.701 days) and Earth (365.256 days) are in an 8 year (2922 days) resonance with each other. In other words, in the time it takes Earth to orbit the Sun eight times, Venus completes almost exactly thirteen revolutions about the Sun. As a result, Venus and Earth line up in the same positions with respect to the Sun. Actually, the two orbital periods are not quite commensurate with each other since Venus arrives at the eight year rendezvous about 22 hours earlier that Earth. By the third eight-year cycle, Venus arrives too early for a transit to occur. The next transit season occurs either 105.5 years or 121.5 years later at the opposite node of Venus' orbit. Once again, a pair of transits will often occur separated by eight years. This recurrence pattern of 8 + 105.5 + 8 + 121.5 years can be seen repeating itself in the catalog of Venus transits. An example of the pattern can be seen in the transits of 1631, 1639, 1761, 1769, 1874, 1882, 2004 and 2012. Occasionally, one of the eight year "double-transits" may disappear from the catalog for several centuries because one of them is a near miss. For instance, note the "missing" transits of 1388, 1145, 0902, 0659, 0416, etc.. A useful way to organize the transits is by grouping them into series where each member of a series is separated by 88,756 days or 243 years (= sum of 8 + 105.5 + 8 + 121.5 years). Thus, the transits of 1518, 1761 and 2004 would belong to one series, while the transits of 1639, 1882 and 2125 <../image/VenusTransit04b.GIF> would belong to another series. Such transit series are quite long-lived and may last 5,000 years or more. For example, Series 4 (December at Ascending Node) <../image/VenusTransit04b.GIF> began in -1763 (1764 BCE) and will run through 2854 (a grazing transit) for a total of 20 transits spanning 4617 years. These transit families are quite analogous to the Saros <../../SEsaros/SEsaros.html> series for solar and lunar eclipses. The position of the orbital nodes of Venus with respect to Earth are slowly changing with time. Five thousand years ago, transits occurred around May 21 and November 19. At present, the transits occur within a day of June 7 and December 9. In about 1500 years, the transits will occur during Earth's solstices (June 21 and December 22). This trend in the shift of transit dates is readily apparent in the catalog below. Over a period of approximately eighty thousand years, the transit dates will migrate forward one complete cycle through the seasons. The following catalog contains predictions for every transit of Venus during the six thousand year interval 2000 BCE through 4000 CE. The information for each transit in the catalog is summarized as follows. The calendar date^6 and geocentric Universal Time^7 of the four transit contacts^8 and the instant of greatest transit^9 are found in the first six columns. The Sun's coordinates (Right Ascension and Declination) and the Greenwich Sidereal Time at 00:00 UT are given next. The minimum separation between the centers of Venus and the Sun is listed in arc-seconds. Finally the transit series^10 is given. The individual columns in each table are described in greater detail in the Key to Transit Catalogs . Blue Bar Blue Bar NASA logo WebMaster: Fred Espenak e-mail: espenak at gsfc.nasa.gov Planetary Systems Branch - Code 693 NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771 USA /Last revised: 2004 Feb 11 - F. Espenak/