Every 1151 years, seven planets of the Solar System, from Mercury to Neptune, find themselves at almost the same points in their orbits. Their positions scatter by less than a degree, as if the celestial mechanism is wound to the same tune. This rhythm was discovered by comparing planetary positions over 2600 years using precise tables of celestial motion.
But one member falls out of step. Uranus lags by a third of an orbit, while its neighbor Neptune is off by only five degrees. Such a gap between the two ice giants looks like a scar from an ancient catastrophe: perhaps, in the Solar System's youth, a large body slammed into Uranus and knocked it off rhythm.
Had that impact never happened, all eight planets might be marching in perfect formation. Instead, in the planetary choir, seven voices sing in harmony, while one is off-key, a reminder of our system's turbulent youth.
as written by the authors arXiv:2604.03049
We report the empirical detection of a multi-planet quasi-commensurability in the Solar System and identify an anomalous exclusion that may bear on the dynamical history of Uranus. An exhaustive search identifies T* = 420,403 days (approx. 1,151 years) as the global minimum of a series-comparison similarity metric applied to daily heliocentric ecliptic longitudes of seven planets -- Mercury, Venus, Earth, Mars, Jupiter, Saturn, and Neptune -- computed from the DE441 ephemeris over +/-1,300 years. At this interval, the mean simultaneous angular displacement of all seven planets is 13.4 degrees, with a standard deviation of 0.65 degrees sustained over a century-long window and stable across 1,200 years of reference epochs. T* ranks first among all 2,600 candidates, with a gap of 1.09 degrees to the second best. No sub-multiple produces a comparable result. Seven of the eight planets participate in the synchronism. The sole exception is Uranus, whose sidereal residue at T* is -108.3 degrees -- nearly one-third of a full orbit -- while Neptune's residue is only -5.2 degrees, one of the smallest among all seven planets after Earth's. This sharp asymmetry between the two ice giants constitutes an independent empirical signature consistent with the hypothesis that Uranus's orbital period was substantially modified by a catastrophic early impact. The interval 1,151 years was identified by Babylonian astronomers as the Venus return period (de Jong 2019); the present work shows it is simultaneously optimal for six additional planets. Source code and data are publicly available.
The 1151-year period was known to Babylonian astronomers as the time for Venus to return to the same spot in the sky — long before Uranus and Neptune were discovered.
Arthur C. Clarke's story "Collision at Dawn" describes a catastrophe that changed a planet's axial tilt, a similar scenario might have happened to Uranus.