Great conjunction

A Great Conjunction is a conjunction of the planets Jupiter and Saturn. The last Great Conjunction took place on May 31, 2000, while the next one will be in late December 2020. Great Conjunctions take place regularly, every 18–20 years, as a result of the combined ~12-year orbital period of Jupiter around the Sun, and Saturn's ~30-year orbital period. The 2000 conjunction fell within mere weeks after both had passed conjunction with the Sun, and it was very difficult to observe without visual aid because the two planets rose only 30–45 minutes before sunrise, depending upon the location of the observer.

Greatest conjunction

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 over a period of a few months.

The so-called "Star of Bethlehem" — thought to have appeared c. 7 BC — was theorized to be a greatest conjunction; and some went so far as to assert that it was an occultation of Saturn by Jupiter, with the two planets appearing to merge into a single object as seen from Earth. However such an event did not take place at historic times. At the greatest conjunction in 7 BC, which is said to be the "Star of Bethlehem", the minimum distance between Jupiter and Saturn was around 1 degree, this is twice the Moon's diameter. The next occultation of Saturn by Jupiter will take place in 7541.

There is no obvious period for the occurrence of greatest conjunctions: the last greatest conjunctions took place in 1682/83, 1821 (only in right ascension), 1940/41 and 1981, while the next one will take place in the year 2238/39.

Great Conjunctions in Right ascension between 1800 and 2100

Date	Time UTC	Planet	Angle distance	Planet	Elongation to sun
July 21, 1802	03:22:00	Jupiter	42' south of	Saturn	37.9° East
June 25, 1821	00:05:09	Jupiter	1°15' north of	Saturn	67.5° West
November 22, 1821	23:49:55	Jupiter	1°20' north of	Saturn	140.2° East
December 23, 1821	09:28:49	Jupiter	1°22' north of	Saturn	108.5° East
January 25, 1842	22:22:31	Jupiter	32' south of	Saturn	26.8° West
October 25, 1861	15:11:20	Jupiter	52' south of	Saturn	43.1° West
April 22, 1881	11:58:20	Jupiter	1°18' north of	Uranus	1.0° East
November 28, 1901	06:10:38	Jupiter	27' south of	Saturn	38.6° East
September 14, 1921	16:22:08	Jupiter	1°02' south of	Saturn	6.2° East
August 15, 1940	13:18:42	Jupiter	1°15' north of	Saturn	97.5° West
October 11, 1940	23:17:26	Jupiter	1°17' north of	Saturn	155.0° West
February 20, 1941	19:14:02	Jupiter	1°21' north of	Saturn	67.7° East
February 18, 1961	14:42:37	Jupiter	14' south of	Saturn	34.6° West
January 14, 1981	07:58:37	Jupiter	1°09' south of	Saturn	103.9° West
February 19, 1981	07:12:10	Jupiter	1°09' south of	Saturn	141.2° West
July 30, 1981	21:32:22	Jupiter	1°12' south of	Saturn	57.9° East
May 31, 2000	10:13:27	Jupiter	1°11' north of	Saturn	16.9° West
December 21, 2020	13:48:52	Jupiter	6' south of	Saturn	30.3° East
November 5, 2040	13:19:46	Jupiter	1°14' south of	Saturn	24.8° West
April 10, 2060	09:01:25	Jupiter	1°09' north of	Saturn	39.8° East
March 15, 2080	08:29:24	Jupiter	6' north of	Saturn	43.8° West
September 24, 2100	01:40:38	Jupiter	1°18' south of	Saturn	25.1° East

Great Conjunctions in ecliptical longitude between 1800 and 2100

Date	Time UTC	Planet	Angle distance	Planet	Elongation to sun
July 17, 1802	22:57:00	Jupiter	39' south of	Saturn	40.6° East
June 19, 1821	16:56:57	Jupiter	1°10' north of	Saturn	63.3° West
January 26, 1842	06:16:53	Jupiter	32' south of	Saturn	27.1° West
October 21, 1861	12:27:02	Jupiter	48' south of	Saturn	39.7° West
April 18, 1881	13:35:59	Jupiter	1°13' north of	Saturn	3.1° East
November 28, 1901	16:37:33	Jupiter	26' south of	Saturn	38.2° East
September 10, 1921	04:13:03	Jupiter	57' south of	Saturn	9.7° East
August 8, 1940	01:13:20	Jupiter	1°11' north of	Saturn	90.9° West
October 20, 1940	04:42:14	Jupiter	1°14' north of	Saturn	164.0° West
February 15, 1941	06:36:25	Jupiter	1°17' north of	Saturn	72.9° East
February 19, 1961	00:07:18	Jupiter	14' south of	Saturn	34.9° West
December 31, 1980	21:17:24	Jupiter	1°03' south of	Saturn	90.9° West
March 4, 1981	19:14:36	Jupiter	1°03' south of	Saturn	155.9° West
July 24, 1981	04:13:35	Jupiter	1°06' south of	Saturn	63.8° East
May 28, 2000	15:56:27	Jupiter	1°09' north of	Saturn	14.9° West
December 21, 2020	18:37:31	Jupiter	6' south of	Saturn	30.1° East
October 31, 2040	12:02:47	Jupiter	1°08' south of	Saturn	20.8° West
April 7, 2060	22:36:24	Jupiter	1°07' north of	Saturn	41.9° East
March 15, 2080	01:49:55	Jupiter	6' north of	Saturn	43.5° West
September 18, 2100	22:50:40	Jupiter	1°13' south of	Saturn	29.4° East

See also

• Triple conjunction