Halley’s Comet Has the Wrong Name, New Research Suggests

Evidence from medieval chronicles suggests that the periodic nature of Halley’s Comet was recognized centuries earlier than previously believed.

Edmond Halley is widely associated with identifying the repeating path of the comet that carries his name, but new research suggests he was not the first to recognize its cycle. According to work by Professor Simon Portegies Zwart and other scholars, a medieval monk made this connection centuries earlier. In the 11th century, Eilmer of Malmesbury appears to have realized that two comet sightings decades apart were of the same object.

Accounts of these observations appear in writings by William of Malmesbury, a chronicler from the 12th century. Despite being preserved in historical texts, this evidence was largely overlooked by modern researchers until now. Portegies Zwart and his coauthor Lewis argue that Eilmer, also known as Aethelmaer, personally witnessed both appearances of the comet. Their analysis is presented in the book ‘Dorestad and Everything After. Ports, townscapes & travellers in Europe, 800-1100’.

Halley identifies the comet’s periodicity

Several centuries later, Edmond Halley used systematic observation and calculation to demonstrate that a bright comet recorded in 1531, 1607, and 1682 was the same object returning on a regular schedule.

This comet, later designated 1P/Halley, follows an orbit that brings it back to the inner solar system roughly every 76 years, a finding that marked a major step forward in astronomical science.

Worldwide observations in 1066

One of the comet’s earlier returns occurred in 1066 and was recorded far beyond Europe. Chinese astronomers observed it for more than two months, providing some of the most detailed early records. The comet reached peak brightness on 22 April 1066, though observers in Brittany and the British Isles did not see it until 24 April.

Its appearance was later immortalized in the Bayeux Tapestry, where it is shown as part of the visual record of the dramatic events of that year.

Comet appearances as omens in medieval chronicles

The comet appeared during the brief reign of King Harold Godwinson, from 6 January to 14 October 1066. Source research by Portegies Zwart and Lewis shows that a comet was seen five times in the centuries around this date. In oral tradition, these appearances are associated with the deaths of kings, war, or famine in the British Isles.

A comet not mentioned in the chronicles, said to precede the death of Archbishop Sigeric of Canterbury in 995, may be interpreted as a historical equivalent of fake news, or as an exaggeration of events, probably intended to frighten the British population with God’s wrath over the sins of the people.

The monk Eilmer – or Aethelmaer – of Malmesbury must already have been elderly when he saw Halley’s Comet for the second time in 1066. He realized that he had seen the same comet earlier, in 989. Once again, as was customary at the time, the king was warned of impending disaster.

Call for reassessment and further research

The researchers argue that Halley’s Comet should be given a different name, as it had already been observed twice centuries earlier. Portegies Zwart says: “This research was great fun to do, but I also found it challenging to work within such an interdisciplinary project alongside a historian. Nevertheless, we plan to carry out further research into this kind of periodic comet.”

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