Science Fair Project Encyclopedia
A triple conjunction is an astronomical event, where two planets or a planet and a star meet each other three times in a short period either in opposition or at the time of inferior conjunction, if an inferior planet is involved. The visible movement of the planet or the planets in the sky is therefore normally prograde at the first conjunction, retrograde at the second conjunction and again prograde at the third conjunction.
There are three possible cases of triple conjunctions.
4 Triple conjunction of the planets Mars, Jupiter, Saturn, Uranus und Neptune in right ascension between 1800 and 2100
Triple conjunctions between Mercury and Venus
At nearly every inferior conjunction there is a triple conjunction between Mercury and Venus. In most cases the second conjunction is not visible, because both planets have a too small elongation from the Sun. Triple conjunctions between Mercury and Venus are also possible, if Mercury and Venus are at the same time in inferior conjunction. This event is much rarer and the second conjunction between Mercury and Venus is also invisible.
Triple conjunctions of inferior planets with superior planets or stars
If Mars is in conjunction with the Sun, there is often a triple conjunction between Mars and Mercury or between Mars and Venus. In the events in which Mercury is involved, the second conjunction is invisible because of small elongation from sun; both other events are difficult to see because of the nearness to horizon and the relatively low brightness of Mars, which is there always near its greatest distance from earth, barely visible.
For a Mars-Venus triple conjunction all three events can almost always be seen, but Mars is dim because of its great distance from the Earth.
Triple conjunctions between the inferior planets Mercury and Venus and the superior planets Jupiter, Saturn, Uranus, Neptune, Pluto or with stars take place when these objects are at the same time in conjunction to sun while Mercury or Venus are at inferior conjunction. Frequently the second conjunction takes place when both bodies are too close to the sun in order to be seen, while the other conjunctions are easily visible, especially if the other body is Jupiter, Saturn or a bright star.
With the dim planets Uranus, Neptune and Pluto the visibility of such an event is difficult, because of the low elongation from Sun.
Triple conjunctions of Mercury and Venus with the exterior planets Jupiter, Saturn, Uranus, Neptune, and Pluto happen relatively frequently (approximately once in 10 years). During the movement in their inferior conjunction loop Mercury and Venus are always involved in triple conjunctions with some stars. Triple conjunctions with bright stars are as frequent as with exterior planets.
Triple conjunctions between two exterior planets
These are the most interesting triple conjunctions, because all three conjunctions can be seen very easily, because of the great elongation of the planets or stars involved. Triple conjunctions between exterior planets or an exterior planet and a star can only occur when these objects are nearly simultaneously in opposition.
Triple conjunctions between the bright exterior planets are very rare: the last triple conjunctions between Mars and Jupiter occurred in 1789-'90, in 1836-'37 and in 1979-'80. The next events of this kind will be again in 2123 and in 2169 -'70 .
The last triple conjunctions between Mars and Saturn took place in 1779, 1877 (only in right ascension) and in 1945-'46. The next triple conjunction between these planets will occur in 2148 -'49 , in 2185 and in 2187 .
For both at triple conjunctions between Mars and Jupiter and for triple conjunctions between Mars and Saturn it is possible that two such events follow at an interval of only 2 years. This last happened for Mars and Jupiter 927 and 929 and will be again in 2742 and 2744 . It last happened for Mars and Saturn in 1742-'43 and 1744-'45 and will occur again in 2185 and 2187 .
The most historically important triple conjunction was that one between Jupiter and Saturn in 7 BCE-5 BCE, which is the most common explanation for the star of Bethlehem. Triple conjunctions between Jupiter and Saturn -- so-called Greatest Conjunctions -- last took place in 1682-'83, 1821 (only in right ascension), 1940-'41 and 1981. It will not occur again until 2238 -'39.
There are more frequent triple conjunctions of Jupiter with Uranus or Neptune. They are unspectacular, but offer a good possibility for amateur astronomers to find these dim planets. The next triple conjunction between Jupiter and Uranus will be in 2010-'11 and the next between Jupiter and Neptune will be in 2009.
At each opposition, because of the visible loop movement of the planets, there are triple conjunctions between the planet and some stars. Triple conjunctions between planets and bright stars close to the zodiac are not so frequent (approximately 2 events in 10 years)
Triple conjunction of the planets Mars, Jupiter, Saturn, Uranus und Neptune in right ascension between 1800 and 2100
- 1821: Uranus-Neptune (March 17th, May 7th, December 2nd)
- 1821: Jupiter-Saturn (June 25th, November 23rd, December 23rd)
- 1836/37: Mars-Jupiter (November 14th, 1836; March 5th, 1837; March 23rd, 1837)
- 1843: Jupiter-Neptune (April 9th, September 15th, November 5th)
- 1845: Mars-Neptune (June 18th, September 2nd, October 3rd)
- 1846: Saturn-Neptune (March 31st, September 14th, December 3rd)
- 1851/52: Saturn-Uranus (July 15th, 1851; October 4th, 1851; March 4th, 1852
- 1877: Mars-Saturn (July 27th, August 26th, November 4th)
- 1888: Mars-Uranus (January 9th, May 5th, June 7th)
- 1896/97: Mars-Neptune (September 24th, 1896; December 12th, 1896;February 19th, 1897)
- 1896/97: Saturn-Uranus (December 28th, 1896; June 19th, 1897; August 26th, 1897)
- 1907: Mars-Uranus (May 2nd, July 19th, August 24th)
- 1919/20: Jupiter-Neptune (September 23rd, 1919; March 13nd, 1920; April 20th, 1920)
- 1927/28: Jupiter-Uranus (July 9th, 1927; August 19th, 1927; January 23rd, 1928)
- 1932/33: Mars-Neptune (December 5th, 1932; March 11th, 1933; May 16th, 1933)
- 1940/41: Jupiter-Saturn (August 15th, 1940; October 12th, 1940; February 20th, 1941)
- 1943/44: Mars-Uranus (September 9th, 1943; December 26th, 1943; January 20th, 1944)
- 1945/46: Mars-Saturn (October 26th, 1945; January 22nd, 1946; March 19th, 1946)
- 1952/53: Saturn-Neptune (November 18th, 1952; May 31st, 1953; July 11th, 1953)
- 1954/55: Jupiter-Uranus (October 8th, 1954; January 6th, 1955; May 10th, 1955)
- 1964/65: Mars-Uranus (December 5th, 1964; April 3rd, 1965; May 6th, 1965)
- 1968/69: Jupiter-Uranus (December 9th, 1968; March 15th, 1969; July 18th, 1969)
- 1971: Jupiter-Neptune (February 2nd, May 20th, September 18th)
- 1979/80: Mars-Jupiter (December 13th, 1979; March 2nd, 1980; May 4th, 1980)
- 1981: Jupiter-Saturn (January 14th, February 19th, July 30th)
- 1983: Jupiter-Uranus (February 17th, May 16th, September 24th)
- 1988: Saturn-Uranus (February 13th, June 27th, October 18th)
- 1989: Saturn-Neptune (March 3rd, June 24th, November 12th)
- 1993: Uranus-Neptune (January 26th, September 17th, September 28th)
- 2009: Jupiter-Neptune (May 25th, July 13th, December 20th)
- 2010/11: Jupiter-Uranus (June 6th, 2010; September 22nd, 2010; January 2nd, 2011)
- 2025/26: Saturn-Neptune (June 29th, 2025; August 6th, 2025; February 16th, 2026)
- 2037/38: Jupiter-Uranus (September 8th, 2037; February 19th, 2038; March 30th, 2038)
- 2041/42: Mars-Uranus (November 2nd, 2041; March 16th, 2042; March 18th, 2042)
- 2047/48: Jupiter-Neptune (July 24th, 2047; November 15th, 2047; February 26th, 2048)
- 2063: Mars-Uranus (February 23rd, May 27th, July 17th)
- 2066: Jupiter-Uranus (January 19th, June 27th, August 18th)
- 2071/72: Mars-Neptune (October 8th, 2071; February 5th, 2072; February 29th, 2072)
- 2079: Saturn-Uranus (February 28th, August 29th, October 23rd)
- 2085/86: Jupiter-Neptune (October 30th, 2085; January 13th, 2086; June 8th, 2086)
- 2088/89: Mars-Neptune (December 14th, 2088; January 4th, 2089; May 13th, 2089)
- 2093: Jupiter-Uranus (May 16th, October 27th, November 30th)
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