In 989, a young Benedictine monk at Malmesbury Abbey in England saw a bright comet cross the sky. Seventy-seven years later, in 1066, he saw it again. According to new research, Eilmer of Malmesbury recognized that both comets were the same object returning through space.
If true, Eilmer understood the comet's periodic nature roughly 600 years before Edmond Halley. The comet is now called Halley's Comet, named after the English astronomer who studied its appearances in 1531, 1607, and 1682. Halley predicted it would return in 1758 but died in 1742, never knowing he was correct.
Professor Simon Portegies Zwart of Leiden University led the new study. He argues that Halley was not the first person to understand the comet's secret. The medieval monk may have discovered it first.
Eilmer's two sightings were about 77 years apart. The comet's actual period is roughly 76 years. This match is striking. William of Malmesbury, a respected historian, recorded Eilmer's observations in the 12th century. Scholars have read these texts for centuries but may have missed their astronomical meaning.
The 1066 comet was visible across the British Isles and appeared in the famous Bayeux Tapestry. It arrived during a dramatic year when King Harold Godwinson ruled England. The comet was widely seen as an omen of change.