the.com/oort cloud

means A vast, distant shell of icy debris surrounding the solar system, believed to be the source of long-period comets.

from Named for Dutch astronomer Jan Oort, who in 1950 proposed its existence not by seeing it but by reasoning backward from comet orbits — noticing that long-period comets arrive from every direction with random tilts, which meant they had to come from a vast spherical reservoir far beyond Pluto rather than a flat disk like the planets. The cloud itself has never been directly observed; it remains a brilliant inference, named after the man who did the math.