Level 1 — Absolute Beginner

Halley's Comet is a famous comet. It comes back to Earth every 76 years. People can see it in the sky.

A long time ago, there was a monk in England. His name was Eilmer. He lived in Malmesbury Abbey.

Eilmer saw the comet two times. He saw it as a boy in 989. He saw it again as an old man in 1066.

Scientists in 2026 say Eilmer knew it was the same comet. He saw the comet about 600 years before Edmond Halley.

comet

a bright body of ice and dust that moves around the sun

sky

the space above the Earth that we can see

monk

a religious man who lives in a special house called an abbey

abbey

a building where monks or nuns live and pray

year

12 months

see

to use your eyes to look at something

boy

a young male person

old

having lived for many years

Level 2 — Elementary

Most people learn at school that Halley's Comet is named after the English astronomer Edmond Halley. In 1705, Halley said the comet was the same one seen in earlier years. He showed that it returns about every 76 years.

But new research published in May 2026 says that someone else worked out this pattern much earlier. An English monk called Eilmer of Malmesbury saw the same comet twice in his long life — once around the year 989, and again in 1066, just before the famous Battle of Hastings.

Astrophysicist Simon Portegies Zwart of Leiden University and historian Bob Zwart Lewis studied medieval texts about Eilmer. They argue that he understood the comet was the same object both times. According to the chronicler William of Malmesbury, Eilmer looked up and said, 'You've come, have you?... It is long since I saw you.'

If the researchers are right, Eilmer recognised the comet's return more than 600 years before Halley. The team published their findings in a book called 'Dorestad and Everything After', and on a science website called arXiv. They suggest that the comet may deserve a different name — but they admit the old name is unlikely to change.

astronomer

a scientist who studies stars, planets, and other space objects

pattern

a regular way that something happens again and again

chronicler

a person in history who wrote down events

medieval

from the Middle Ages, about the years 500–1500

research

careful study of something to learn more about it

return

to come back to the same place

famous

well known to many people

object

a thing that you can see or touch

Level 3 — Intermediate

When most people think of Halley's Comet, they picture the English astronomer Edmond Halley, who in 1705 used Newton's new laws of motion to argue that the bright comets observed in 1531, 1607, and 1682 were one and the same object on a roughly 76-year orbit. He successfully predicted its return in 1758, and the comet has carried his name ever since. New research released in May 2026, however, makes the case that the credit for first recognising the comet's periodicity should be shared with a far older observer.

Astrophysicist Simon Portegies Zwart of Leiden University and historian Bob Zwart Lewis re-examined accounts of Eilmer of Malmesbury, a Benedictine monk who lived at Malmesbury Abbey in southwest England from roughly the late tenth into the late eleventh century. Eilmer is best known to popular history for an early gliding experiment using strapped-on wings, but the 2026 paper focuses instead on his astronomical memory: he observed a bright comet as a child around 989 and saw it again as an old man in 1066, just months before the Norman Conquest.

The strongest evidence is a passage in the 'Gesta Regum Anglorum' by the 12th-century chronicler William of Malmesbury, who knew Eilmer personally. William records that, on seeing the 1066 apparition, the elderly monk addressed the comet directly: 'You've come, have you?... It is long since I saw you; but as I see you now, you are much more terrible, for I see you brandishing the downfall of my mother country.' Portegies Zwart and Lewis argue that this is not poetic flourish but the deliberate identification of two appearances of the same body, separated by the comet's true mean period of about 76 years.

The findings were published in the volume 'Dorestad and Everything After: Ports, Townscapes & Travellers in Europe, 800–1100' and shared on the arXiv preprint server. The authors acknowledge that names of astronomical objects rarely change in practice; the International Astronomical Union sticks closely to Halley because the prediction of a return is what proves periodicity. Still, they hope the work prompts greater recognition of medieval observers — and of how much careful science was already happening in the cloisters and observatories of pre-modern Europe.

periodicity

the property of repeating at regular intervals

orbit

the curved path of one object around another in space

Benedictine

belonging to a Christian religious order founded by Saint Benedict

apparition

an appearance of a comet or other object that can be seen from Earth

chronicler

a person who records events of their time in writing

preprint

a scientific paper made public before formal peer review and journal publication

mean period

the average time it takes a body to complete one orbit

Level 4 — Advanced

The name 'Halley's Comet' is so deeply embedded in scientific shorthand that it is easy to forget how recent — and how contingent — it is. Edmond Halley's claim to the comet rests on a single brilliant induction: that the bright apparitions of 1531, 1607, and 1682, recorded in turn by Apian, Kepler, and Hevelius, were a single periodic object whose return he predicted, with the help of Newtonian dynamics, for 1758. A new study released in May 2026 by Simon Portegies Zwart of Leiden University and historian Bob Zwart Lewis argues that an analogous inference was made nearly 700 years earlier by Eilmer of Malmesbury, and that the historical credit should be re-examined accordingly.

Eilmer was a Benedictine monk at the abbey of Malmesbury in Wessex, plausibly born around 980. He is most often invoked for a celebrated proto-aeronautical leap from the abbey tower, but Portegies Zwart and Lewis foreground his astronomical biography. As a child he reportedly saw the bright comet of 989; as an elderly man — eighty or so years later — he witnessed the apparition of 1066, recorded contemporaneously across Latin Christendom and immortalised on the Bayeux Tapestry. The chronicler William of Malmesbury, who lived in the cloister some decades after Eilmer, preserves a passage in the 'Gesta Regum Anglorum' in which the aged monk addresses the comet directly, framing it as a returning visitor rather than a novel sign.

The 2026 paper integrates orbital mechanics with codicology. Modern integrations confirm that the 989 and 1066 perihelia of comet 1P/Halley fall within Eilmer's plausible observational lifetime, with a mean inter-apparition interval of roughly 77 years — within a few percent of the comet's true mean period. The authors note that the manuscript tradition for William's text is stable and that the rhetorical structure of Eilmer's outburst presupposes the identity of the two objects, not merely a vague resemblance. Whether this constitutes 'discovery' of periodicity in the strict sense — predicting a future return — is, the authors concede, a question of definition.

The findings appear in the multi-author volume 'Dorestad and Everything After: Ports, Townscapes & Travellers in Europe, 800–1100' and as a preprint on arXiv (2511.14809). The International Astronomical Union almost certainly will not rename comet 1P, both because of the cost to a four-century-old scientific vocabulary and because Halley's quantitative prediction remains the procedural watershed. But the work joins a wider literature reframing medieval natural philosophy — from Bede's tides to Walcher of Malvern's eclipse tables — as an underappreciated chapter in the history of observational science, and it offers a useful corrective to the easy nineteenth-century assumption that systematic astronomy began only with Newton's heirs.

induction

a way of reasoning that draws a general law from specific observations

perihelion

the point in an orbit at which a body is closest to the Sun