Thursday, April 10, 2014

Halley's Comet

Halley's Comet on the Bayeaux Tapestry
The nice thing about astronomy is that some celestial events are so predictably cyclical that they can help confirm dates in history, or be spotted in the historical record. Halley's Comet has appeared numerous times while human beings have been on Earth, and many of those appearances have been noted by record-keepers.

BCE records suggest Halley's was spotted as early as 467 BCE by the Greeks and the Chinese, but the first report detailed enough to be certain of Halley's pattern was in 240 BCE by a Chinese chronicle.

The 1493 Nuremberg Chronicles used many early sources, one of which mentioned the comet appearing over Europe in 684. The 837 approach—recorded by astronomers in Germany as well as across the Middle East and Asia—was the closest the comet ever came to earth: a mere 3.2 million miles away, and took place on 10 April. The Annals of Ulster—an Irish chronicle extending from 431 to 1540 CE—says of 912 "A dark and rainy year. A comet appeared."

1066 saw the appearance of an invading Norman army in England and the appearance of the comet in the Anglo-Saxon Chronicle, in the Irish Annals of the Four Masters, and later in the Bayeaux Tapestry.

Drawing and note from Eadwine Psalter
The Bayeaux Tapestry wasn't the only attempt to record visually what they saw in the sky. The 1145 appearance was drawn up by a monk, Eadwine, who was copying a psalter at Canterbury Cathedral. On the bottom of the page with the Fifth Psalm, Eadwine added a drawing and a note: “Concerning the star ‘comet’. The star ‘comet’ has a ray such as this, and in English it is called the long-haired star.* It appears rarely during the course of many years, and then as a portent.”

The next appearance of Halley's is scheduled for 28 July 2061.

*comet is from Greek and means "hair" or "long hair."

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