Great conjunction

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A great conjunction is a conjunction of the planets Jupiter and Saturn.[note 1] Great conjunctions occur regularly, about every 20 years, due to the combined effect of Jupiter's approximately 12-year orbital period and Saturn's approximately 30-year orbital period.

The most recent great conjunction occurred on 31 May 2000; the next one will be in late December 2020. The 2000 conjunction fell within mere weeks after both planets had passed their conjunctions with the Sun; hence, the event was difficult to observe without visual aid because the pair rose only 30–45 minutes before sunrise, depending on the location of the observer.

A greatest conjunction is a conjunction of Jupiter and Saturn at or near their opposition to the Sun. In this scenario, Jupiter and Saturn will occupy the same position in right ascension on three separate occasions (due to apparent retrograde motion) over a period of a few months. Such tripled occurrences are actually known as triple conjunctions.

In the years 1800 to 2100[edit]

Great conjunctions in right ascension
Date Time
(UTC)
Angular distance
from Jupiter to Saturn
Elongation
from Saturn to the Sun
Zodiac sign
21 July 1802 03:22:00 42' South 37.9° East Virgo
25 June 1821 00:05:09 1°15' North 67.5° West Aries
22 November 1821 23:49:55 1°20' North 140.2° East Aries
23 December 1821 09:28:49 1°22' North 108.5° East Aries
25 January 1842 22:22:31 32' South 26.8° West Capricorn
25 October 1861 15:11:20 52' South 43.1° West Virgo
22 April 1881 11:58:20 1°18' North 1.0° East Taurus
28 November 1901 06:10:38 27' South 38.6° East Capricorn
14 September 1921 16:22:08 1°02' South 6.2° East Virgo
15 August 1940 13:18:42 1°15' North 97.5° West Taurus
11 October 1940 23:17:26 1°17' North 155.0° West Taurus
20 February 1941 19:14:02 1°21' North 67.7° East Taurus
18 February 1961 14:42:37 14' South 34.6° West Capricorn
14 January 1981 07:58:37 1°09' South 103.9° West Libra
19 February 1981 07:12:10 1°09' South 141.2° West Libra
30 July 1981 21:32:22 1°12' South 57.9° East Libra
31 May 2000 10:13:27 1°11' North 16.9° West Taurus
21 December 2020 13:22 6' South 30.3° East Aquarius
5 November 2040 13:19:46 1°14' South 24.8° West Libra
10 April 2060 09:01:25 1°09' North 39.8° East Gemini
15 March 2080 08:29:24 6' North 43.8° West Aquarius
24 September 2100 01:40:38 1°18' South 25.1° East Libra
Great conjunctions in ecliptic longitude
Date Time
(UTC)
Angular distance
from Jupiter to Saturn
Elongation
from Saturn to the Sun
Zodiac sign
17 July 1802 22:57:00 39' South 40.6° East Virgo
19 June 1821 16:56:57 1°10' North 63.3° West Aries
26 January 1842 06:16:53 32' South 27.1° West Capricorn
21 October 1861 12:27:02 48' South 39.7° West Virgo
18 April 1881 13:35:59 1°13' North 3.1° East Taurus
28 November 1901 16:37:33 26' South 38.2° East Capricorn
10 September 1921 04:13:03 57' South 9.7° East Virgo
8 August 1940 01:13:20 1°11' North 90.9° West Taurus
20 October 1940 04:42:14 1°14' North 164.0° West Taurus
15 February 1941 06:36:25 1°17' North 72.9° East Taurus
19 February 1961 00:07:18 14' South 34.9° West Capricorn
31 December 1980 21:17:24 1°03' South 90.9° West Libra
4 March 1981 19:14:36 1°03' South 155.9° West Libra
24 July 1981 04:13:35 1°06' South 63.8° East Libra
28 May 2000 15:56:27 1°09' North 14.9° West Taurus
21 December 2020 18:37:31 6' South 30.1° East Aquarius
31 October 2040 12:02:47 1°08' South 20.8° West Libra
7 April 2060 22:36:24 1°07' North 41.9° East Gemini
15 March 2080 01:49:55 6' North 43.5° West Capricorn
18 September 2100 22:50:40 1°13' South 29.4° East Libra

As omens[edit]

Great conjunctions have attracted considerable attention as celestial omens. There has been some speculation,[by whom?] for example, that the so-called "Star of Bethlehem" was a great conjunction that occurred c. 7 BCE.[1] During the late Middle Ages and the Renaissance, great conjunctions were a topic broached by most astronomers of the period up to the times of Tycho Brahe and Kepler, by scholastic thinkers as Roger Bacon[2] or Pierre d'Ailly,[3] and they are mentioned in popular and literary writing by authors such as Dante[4] or Shakespeare.[5] This interest is traced back in Europe to the translations from Arabian sources, most notably Albumasar's book on conjunction.[6]

As successive great conjunctions occur nearly 120° apart, their appearances form a triangular pattern. In a series every fourth conjunction returns after some 60 years in the vicinity of the first. These returns are observed to be shifted by some 7–8°, so no more than four of them occur in the same zodiacal sign. To each triangular pattern astrologers have ascribed one from the series of four elements and thus four triplicities or trigons are formed. Particular importance has been accorded to the occurrence of a great conjunction in a new trigon, which is bound to happen after some 200 years at most.[7] Even greater importance was attributed to the beginning of a new cycle after all fours trigons had been visited, something which happens in about 800 years. Since each 'element' (trigon) consists of 3 signs it takes 800x3=2400 for the whole process to start anew (relation with the cycle of Precession).

Kepler's trigon, a diagram of great conjunctions (from the book De Stella Nova (1606) by Johannes Kepler)

Originally a trigon was thought[by whom?] to last 240 years, and the full cycle 960 years; but later more correct estimation were provided by the Alphonsine tables.[4] Despite the inaccuracies and some disagreement about the beginning of the cycle the belief in the significance of such events generated a stream of publications which grew steadily up to the end of the 16th century. As the great conjunction of 1583 was the last in the watery trigon it was widely supposed to herald apocalyptic changes; a papal bull against divinations was issued in 1586 and as nothing really significant had happened by 1603 with the advent of a new trigon, the public interest rapidly died.

See also[edit]

Notes[edit]

  1. ^ "Orbital Motion Simulation of Jupiter and Saturn". GeoGebra.

References[edit]

  1. ^ Michael R. Molnar: The Star of Bethlehem: The Legacy of the Magi, Rutgers University Press, 1999
  2. ^ The Opus Majus of Roger Bacon, ed. J. H. Bridges, Oxford:Clarendon Press, 1897, Vol. I, p. 263.
  3. ^ De concordia astronomice veritatis et narrationis historice (1414) [1]
  4. ^ a b Woody K., Dante and the Doctrine of the Great Conjunctions,Dante Studies, with the Annual Report of the Dante Society, No. 95 (1977), pp. 119–134
  5. ^ Aston M., The Fiery Trigon Conjunction: An Elizabethan Astrological Prediction, Isis, Vol. 61, No. 2 (Summer, 1970), pp. 158–187
  6. ^ De magnis coniunctionibus was translated in the 12th century, a modern edition-translation by K. Yamamoto and Ch. Burnett, Leiden, 2000
  7. ^ Etz D., (2000), Conjunctions of Jupiter and Saturn, Journal of the Royal Astronomical Society of Canada, Vol. 94, p.174 [2]

External links[edit]