The Great Conjunction

The Great Conjunction

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Because they are the slowest moving planets orbiting the sun, 12 years for Jupiter and 29.5 years for Saturn, what the ancient skywatchers called the 'celestial summit meeting' or conjunction , the close alignment of the planets, is a rare event


This will be the case tonight, December 21st, and the planets will line up quite closely, and more so than in the already infrequent occasions, but without giving the impression to merge entirely, remaining separated by approx. one-fifth the width of the moon 

Credit NASA/JPL - Caltech

According to Joe Rao, of, who knows how to make the calculations, such close alignments are quite rare - occuring only twice in the last one thousand years, on March 5, 1226 and on July 16, 1665 (397 years ago) 

But not to worry, we will have another chance on March 15, 2080...


The unique event in the skies above us brings back in our memory Tycho Brahe, the Danish astronomer (1546-1601) whose fame has been obscured by Galileo (born 1564) and Johannes Kepler (born 1571), even though they benefitted from Tycho's meticulous observations

source - Wikipedia

After university studies in Copenhagen and Leipzig, later at the universities of Wittenberg, Rostock, and Basel, Tycho Brahe returned to Denmark at the age of 24

In 1572 Tycho observed a new star in the Cassiopeia constellation and published a brief tract "De Nova Stella" about it the following year

Astronomers use an effect called parallax to measure distances to nearby stars against the more distant background stars by taking measurements periodically and calculating the apparent change in position, and in Tycho's time, the moon itself was the reference against which measurements were taken

The lack of detectable parallax led Tycho Brahe to assume the nova might be located beyond the sphere of the moon, in the celestial realm, supposedly unalterable according to Aristotelian doctrine

To resolve the conflict between Aristotelian theory and experimental observation on a scientific basis, Tycho was to dedicate his life to the accuracy of celestial measurements, laying the foundations of modern astronomy

The Danish king, Frederick II, funded an observatory for Tycho Brahe's scientific studies, Uraniburg, which was built between 1576 and 1580 on an island in the Øresund near Copenhagen, to be the first  specialized astronomical institution in Europe

By designing and building the astronomical instruments, by calibrating and checking the instruments for accuracy continually, Tycho Brahe assembled data of unequalled accuracy on which the next generations of astronomers were to rely to advance the science

Constructed from 1576, the Azimuthal Quadrant was used for observations of the 1577 comet, which remained visible from November 1577 to January 1578

1576 Brass Azimuthal Quadrant - sce NCAR-HAO

Again lacking measurable paralax, the comet had to be located beyond the sphere of the moon, just like the nova of 1572 and its movement across the skies led to the assumption of a 'fluid heaven', quite the opposite of the long-held belief that planets formed the kernel of hard, critalline, concentric shells 

The Globe Globe was used to record the position of stars observed by Tycho

1580 - Great Globe - sce NCAR-HAO

By 1595 Tycho Brahe had 1000 accurately observed stars inscribed on the globe

The 1585 "armillary sphere", a model of objects in the sky, was a great improvement on the original 1581 sphere, abandoned because of its inaccuracy, as the weight of the components bended the contraption out of shape

3 meters in diameter - sce NCAR-HAO

Large but bare bones instruments such as this armillary, with improved sighting devices and measuring scales, as well as Tycho's advanced procedures to correct for atmospheric refraction, allowed him to compute stellar and planetary positions consistently accurate to within a minute of arc

And of course, there were others instruments developed over the years by Tycho, such as the Triangular Sextant (1.6 meter in diameter, built in 1582) or  the Revolving Wooden Quadrant (1586), replaced in 1588 by a steel version, all of which were testimony to never-ending experimentation of  Tycho's modernity, a scientific mind bend on achieving understanding through utmost precision

In a tempestuous relationship with Christian IV, who succeeded Frederick in 1588, Tycho packed up, instruments and all, and left in 1597, aged 51, settling in Prague in 1599 where he died two years later...(and where the instruments were put in storage ...and lost)

Perhaps Tyco's last gift to science was to invite Kepler (aged 29) to Prague,  as an assistant to calculate planetary orbits from his most precise observations, which he did, proving the elliptical orbit of the planets for the first time

In many ways,  and even though he kept the Earth at the center of his stellar universe (recoiling from undermining the fundamental tenet of physics - all heavy bodies fall to earth, don't they ?), Tycho Brahe prepared the field for the next generation of astronomers, which were to deliver the visionary insights of the 17th century




Back to the refined calculations of Joe Rao, on, we will quote, as a closing observation of sort,  a very singular alignment of the planets.. in 7 BC

Quoting Joe of the more popular theories for the "Christmas Star" was a series of conjunction between Jupiter and Saturn in 7 BC. For in that year Jupiter and Saturn met not once but three times  (in May, September and December).

The first conjunction (on May 29 — visible "in the east" before sunrise) presumably started the Magi on their way to Bethlehem from the Far East. The middle conjunction (September 30) may have strengthened their resolve in the purpose of their journey, while the third and final conjunction (Dec. 5) occurred just as they arrived in Judea to meet with King Herod, who sent them on to Bethlehem to "go and search diligently for the young child."

credit - Unsplash - Tom Gainor