Halley's Comet is the only known short-period comet that is consistently visible to the naked eye from Earth,

Spellings of Halley's name during his lifetime included Hailey, Haley, Hayley, Halley, Haly, Hawley, and Hawly, so its contemporary pronunciation is uncertain, but the version rhyming with valley seems to be preferred by modern bearers of the surname.

Orbit and origin

Halley's orbital period has varied between 74 and 80 years since 240 BC.

Halley has probably been in its current orbit for 16,000–200,000 years, although it is not possible to numerically integrate its orbit for more than a few tens of apparitions, and close approaches before 837 AD can only be verified from recorded observations.

The apparition of 12 BC was recorded in the Book of Han by Chinese astronomers of the Han dynasty who tracked it from August through October.

The 141 AD apparition was recorded in Chinese chronicles, with observations of a bluish white comet on 27 and 16 March, 22 April and 23.

The 374&nbsp;AD and 607 approaches each came within 0.09&nbsp;au of Earth.</blockquote>

The Irish Annals of the Four Masters recorded the comet as "A star [that] appeared on the seventh of the Calends of May, on Tuesday after Little Easter, than whose light the brilliance or light of The Moon was not greater; and it was visible to all in this manner till the end of four nights afterwards." </blockquote>

1145–1378

thumb|upright=1.3|The [[Adoration of the Magi (circa 1305) by Giotto, who may have modelled the Star of Bethlehem on Halley's Comet, which had been sighted 4 years before this picture was painted.|alt=The wise men and several animals cluster around the baby Jesus, while a comet-like object streaks overhead]]

The 1145 apparition may have been recorded by the monk Eadwine.

The 1301 apparition was visually spectacular, and may be the first that resulted in convincing portraits of a particular comet. The Florentine chronicler Giovanni Villani wrote that the comet left "great trails of fumes behind", and that it remained visible from September 1301 until January 1302. as well as in East Asian sources.

1456

In 1456, the year of Halley's next apparition, the Ottoman Empire invaded the Kingdom of Hungary, culminating in the siege of Belgrade in July of that year. In a papal bull, Pope Callixtus III ordered special prayers be said for the city's protection. In 1470, the humanist scholar Bartolomeo Platina wrote in his ' that,

After witnessing a bright light in the sky which most historians have identified as Halley's Comet, Zara Yaqob, Emperor of Ethiopia from 1434 to 1468, founded the city of Debre Berhan (tr. City of Light) and made it his capital for the remainder of his reign.

1531–1759

thumb|Illustration of the 1531 appearance in Petrus Apianus' [[Astronomicum Caesareum, noting that a comet's tail always points away from the sun]]

In the Sikh scriptures of the Guru Granth Sahib, the founder of the faith, Guru Nanak, makes reference to "a long star that has risen" at Ang 1110, and it is believed by some Sikh scholars to be a reference to Halley's appearance in 1531.

2061

thumb|Animation of 1P/Halley orbit – 2061 apparition<br />

The next perihelion of Halley's Comet is predicted for 28 July 2061,

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Bibliography

  • Synopsis of the Astronomy of Comets (1706 reprint of Halley's 1705 paper)
  • Image of Halley's Comet by the Giotto spacecraft
  • seds.org, links to images and further information about Halley's Comet
  • Photographs of 1910 approach from the Lick Observatory Records Digital Archive
  • HDR Astrophotography: Simulations Atlas of Past Comets (Antiquity to 1699) by Nicolas Lefaudeux
  • HDR Astrophotography: Simulations Atlas of Past Comets (1900 to 1999) by Nicolas Lefaudeux