The great Halley's Comet disappointment of 1986 — and the discoveries that changed astronomy forever

In 1986, expectations surrounding the appearance of Halley’s Comet were significantly lowered by its unexpectedly faint visibility for observers worldwide. However, this apparent disappointment spurred an ambitious international effort involving multiple spacecraft to study the comet up close. The Voyager 2 and Voyager 1 probes, launched earlier that year, were tasked with investigating Halley’s Comet as they traversed their respective trajectories through interstellar space. These robotic explorers provided unprecedented data regarding the comet’s composition, structure, and behavior. Ultimately, the mission yielded groundbreaking discoveries about cometary nuclei, revealing a surprisingly solid and complex interior rather than the expected loosely aggregated material.