Jupiter and Saturn's great conjunctions repeat every ~120°, Saturn's path relative to Jupiter in blue. The closeness is the result of the conjunction occurring in the vicinity of one of the two longitudes where the two orbits appear to intersect when viewed from the Sun (which has a point of view similar to Earth). During the 2020 great conjunction, the two planets were separated in the sky by 6 arcminutes at their closest point, which was the closest distance between the two planets since 1623. The most recent great conjunction occurred on 21 December 2020, and the next will occur on 4 November 2040. The most recent triple conjunction occurred in 1980–81 and the next will be in 2238–39. In this scenario, Jupiter and Saturn will occupy the same right ascension on three occasions or same ecliptic longitude on three occasions, depending on which definition of 'conjunction' one uses (this is due to apparent retrograde motion and happens within months). Occasionally there is more than one great conjunction in a season, which happens whenever they're close enough to opposition: this is called a triple conjunction (which is not exclusive to great conjunctions). (See table below.) Since the equivalent periods of other naked-eye planet pairs are all under 900 days, this makes great conjunctions the rarest. This is about 52 days less than 20 years, but in practice, Earth's orbit size can cause great conjunctions to reoccur anytime between 18 years 10 months and 20 years 8 months after the previous one. In which J and S are the orbital periods of Jupiter (4332.59 days) and Saturn (10759.22 days), respectively. This number can be calculated by the synodic period formulaġ ( 1 J − 1 S ) ≈ 7253.46 d a y s, On average, great conjunction seasons occur once every 19.859 Julian years (each of which is 365.25 days). Main article: Celestial mechanics Diagram showing the movements of Jupiter and Saturn during the 1980–81 triple conjunction

Further repeats of the 516-year period lead to the clustering in AD 1524, considered ominous in Europe at the time of the Radical Reformation, and the upcoming clustering of September 2040, which will involve all five planets again, in a longitude span of less than 7°. The intervals involved, of 377.8 years (19 great conjunction intervals) and 516.4 years (26 great conjunction intervals) bring Mars back to approximately the same position. These were connected in Chinese thought to the founding of the first three historical dynasties, the Xia dynasty, the Shang dynasty, and the Zhou dynasty. The Chinese apparently remembered the clustering of all five planets in 1953 BC, and noted the clustering of all but Venus in 1576 BC and of all five in 1059 BC. Ĭlusterings of several planets were considered even more significant. This interest is traced back in Europe to translations of Arabic texts, especially Albumasar's book on conjunctions. During the late Middle Ages and Renaissance they were a topic broached by the pre-scientific and transitional astronomer-astrologers of the period up to the time of Tycho Brahe and Johannes Kepler, by scholastic thinkers such as Roger Bacon and Pierre d'Ailly, and they are mentioned in popular and literary works by authors such as Dante Lope de Vega and Shakespeare. Great conjunctions attracted considerable attention in the past as omens. See also: Astrological aspect § Great conjunctions Very close conjunctions happen much less frequently (though the maximum of 1.3° is still close by inner planet standards): separations of less than 10 arcminutes have only happened four times since 1200, most recently in 2020. The spacing between the planets varies from conjunction to conjunction with most events being 0.5 to 1.3 degrees (30 to 78 arcminutes, or 1 to 2.5 times the width of a full moon). They are named 'great' for being by far the rarest of the conjunctions between naked-eye planets (i.e.

Great conjunctions occur approximately every 20 years when Jupiter 'overtakes' Saturn in its orbit. The moons Io, Ganymede, Europa, and Titan are visible.Ī great conjunction is a conjunction of the planets Jupiter and Saturn, when the two planets appear closest together in the sky. Stacked photograph of the great conjunction of 2020 four hours before closest approach, with Jupiter 6–7 arcminutes below Saturn. Conjunction of the planets Jupiter and Saturn

Grand trine 2020