Great conjunction

A great conjunction is a conjunction of the planets Jupiter and Saturn.[note 1] Great conjunctions occur regularly (every 19.6 years, on average) due to the combined effect of Jupiter's approximately 11.86-year orbital period and Saturn's 29.5-year orbital period.

Conjunctions occur in at least two separate coordinate systems. The conjunctions in right ascension occur in a coordinate system measured by a set of coordinates based on the celestial equator. This great circle is a projection of the earth's equator into the sky. The second system is based on the ecliptic, the plane of the solar system. When measured along the ecliptic, the separations are usually smaller. Additionally, it is important to note that the exact moment of a conjunction cannot be seen by every observer because the two planets are not in the sky for everybody. So the observer's location must be taken into account. So this third system takes in the closest point of an observer. This is usually very close to the calculated date and time in the ecliptic coordinate system. See the charts below for the differences in time.

List of great conjunctions (1800 to 2100)

In the chart that follows, the elongation indicates the separation of Saturn from the Sun. Low elongations indicate that the conjunction is difficult to see because of the proximity to the Sun.

Great conjunctions in right ascension
Date Time
(UTC)		 Angular distance
from Jupiter to Saturn		 Elongation
from Saturn to the Sun		 Constellation Notes
21 July 1802 03:22:00 42' South 37.9° East Leo
25 June 1821 00:05:09 1°15' North 67.5° West Pisces Triple conjunction
22 November 1821 23:49:55 1°20' North 140.2° East Pisces
23 December 1821 09:28:49 1°22' North 108.5° East Pisces
25 January 1842 22:22:31 32' South 26.8° West Sagittarius
25 October 1861 15:11:20 52' South 43.1° West Leo
22 April 1881 11:58:20 1°18' North 1.0° East Aries Too close to the Sun to be visible
28 November 1901 06:10:38 27' South 38.6° East Sagittarius
14 September 1921 16:22:08 1°02' South 6.2° East Leo Too close to the Sun to be visible
15 August 1940 13:18:42 1°15' North 97.5° West Aries Triple conjunction
11 October 1940 23:17:26 1°17' North 155.0° West Aries
20 February 1941 19:14:02 1°21' North 67.7° East Aries
18 February 1961 14:42:37 14' South 34.6° West Sagittarius
14 January 1981 07:58:37 1°09' South 103.9° West Virgo Triple conjunction
19 February 1981 07:12:10 1°09' South 141.2° West Virgo
30 July 1981 21:32:22 1°12' South 57.9° East Virgo
31 May 2000 10:13:27 1°11' North 16.9° West Aries Difficult to see
21 December 2020 13:22:00 6' South 30.3° East Capricornus Closest since 1623
5 November 2040 13:19:46 1°14' South 24.8° West Virgo
10 April 2060 09:01:25 1°09' North 39.8° East Taurus
15 March 2080 08:29:24 6' North 43.8° West Capricornus
24 September 2100 01:40:38 1°18' South 25.1° East Virgo
Great conjunctions in ecliptic longitude
Date Time
(UTC)		 Angular distance
from Jupiter to Saturn		 Elongation
from Saturn to the Sun		 Constellation Notes
17 July 1802 22:57:00 39' South 40.6° East Leo
19 June 1821 16:56:57 1°10' North 63.3° West Pisces
26 January 1842 06:16:53 32' South 27.1° West Sagittarius
21 October 1861 12:27:02 48' South 39.7° West Leo
18 April 1881 13:35:59 1°13' North 3.1° East Aries Too close to the Sun to be visible
28 November 1901 16:37:33 26' South 38.2° East Sagittarius
10 September 1921 04:13:03 57' South 9.7° East Leo Too close to the Sun to be visible
8 August 1940 01:13:20 1°11' North 90.9° West Aries Triple conjunction
20 October 1940 04:42:14 1°14' North 164.0° West Aries
15 February 1941 06:36:25 1°17' North 72.9° East Aries
19 February 1961 00:07:18 14' South 34.9° West Sagittarius
31 December 1980 21:17:24 1°03' South 90.9° West Virgo Triple conjunction
4 March 1981 19:14:36 1°03' South 155.9° West Virgo
24 July 1981 04:13:35 1°06' South 63.8° East Virgo
28 May 2000 15:56:27 1°09' North 14.9° West Aries Difficult to see
21 December 2020 18:37:31 6' South 30.1° East Capricornus Closest since 1623
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 Taurus
15 March 2080 01:49:55 6' North 43.5° West Sagittarius
18 September 2100 22:50:40 1°13' South 29.4° East Virgo

Notable great conjunctions

When studying the great conjunction of 1603, Johannes Kepler thought that the Star of Bethlehem might have been the occurrence of a great conjunction. He calculated that a triple conjunction of Jupiter and Saturn occurred in 7 BC.[1][2] A triple 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 (or ecliptic longitude) on three separate occasions (due to apparent retrograde motion) over a period of a few months. The most recent triple conjunction occurred in 1981, and the next will occur in 2239.

The 2000 great 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.

The great conjunction of 2020 will be the closest since 1623. At this time Jupiter will be 0.1 degrees south of Saturn, when both planets are 30° from the Sun. Both planets will be visible in the same telescopic field of view.[3] The two planets will be visible to the unaided eye as a single 'star' low above the southwestern horizon in the constellation of Capricornus after sunset.

As omens

Great conjunctions have attracted considerable attention as celestial omens. 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[4] or Pierre d'Ailly,[5] and they are mentioned in popular and literary writing by authors such as Dante[6] and Shakespeare.[7] This interest is traced back in Europe to the translations from Arabian sources, most notably Albumasar's book on conjunction.[8]

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 to 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.[9] 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 800 × 3 = 2400 years 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 to last 240 years, and the full cycle 960 years; but later more correct estimations were provided by the Alphonsine tables.[6] 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.

gollark: Which is a nigh-meaningless distinction.
gollark: You CAN say this and it's pretty true.
gollark: It's... not necessarily actually wrong, though?
gollark: Suuuuuure it was.
gollark: > I disagree, I think it's a good idea

See also

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

References
  1. "1937JRASC..31..417B Page 417". adsabs.harvard.edu. Retrieved 27 May 2020.
  2. Michael R. Molnar: The Star of Bethlehem: The Legacy of the Magi, Rutgers University Press, 1999
  3. "2020: December 21: The Great Conjunction of Jupiter and Saturn". When the Curves Line Up. 11 December 2019. Retrieved 11 August 2020.
  4. The Opus Majus of Roger Bacon, ed. J. H. Bridges, Oxford:Clarendon Press, 1897, Vol. I, p. 263.
  5. De concordia astronomice veritatis et narrationis historice (1414)
  6. 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
  7. Aston M., The Fiery Trigon Conjunction: An Elizabethan Astrological Prediction, Isis, Vol. 61, No. 2 (Summer, 1970), pp. 158–187
  8. De magnis coniunctionibus was translated in the 12th century, a modern edition-translation by K. Yamamoto and Ch. Burnett, Leiden, 2000
  9. Etz D., (2000), Conjunctions of Jupiter and Saturn, Journal of the Royal Astronomical Society of Canada, Vol. 94, p.174
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.