Neptune: A Planet Found by Calculation in 1846

Neptune was found on 23 September 1846 by Johann Galle and Heinrich d'Arrest at the Berlin Observatory, within a degree of the position predicted by Urbain Le Verrier from irregularities in the motion of Uranus; John Couch Adams in England had reached a similar prediction independently, and the resulting priority dispute was bitter. It remains one of the most celebrated confirmations of Newtonian mechanics, a planet located by mathematics before it was seen. Neptune takes about one hundred and sixty-five years to circle the zodiac, some fourteen years to a sign, so that a whole generation shares its sign position and the planet functions in natal work more as a generational marker than as a personal one. Its astrological meaning is therefore under two centuries old, and it appears in no source before the mid-nineteenth century.

Neptune's astrological meaning is under two centuries old, and the essential-dignity table most classical and traditional astrologers still use assigns it no rulership at all, keeping Pisces under Jupiter alone as it was reckoned for roughly two thousand years before the nineteenth century; the now-common practice of giving Neptune co-rulership or outright rulership of Pisces is a later innovation added on top of, rather than replacing, the older dignity scheme most traditional practitioners still follow. The bitter priority dispute between Urbain Le Verrier in France and John Couch Adams in England over who first predicted the planet's position, each having calculated it independently from the same irregularities in Uranus's orbit, was never fully resolved to either nation's satisfaction and is still cited as a case study in the risks of simultaneous, uncoordinated discovery in the history of science.