Comet Halley

Comet Halley, officially designated 1P/Halley, more generally known as Halley's Comet after Edmond Halley, is the best-known and the brightest of the "short-period" comets from the Kuiper belt that visit the inner solar system in years or decades-long orbits rather than the millennial periods of comets from the Oort cloud.

Early history

Having perceived that the elements of the comet of 1682 were nearly the same as those of two comets which had appeared in 1531 (observed by Petrus Apianus) and 1607 (observed by Johannes Kepler in Prague), Halley concluded that all three comets were in fact the same object returning every 76 years (a period that has since been amended to every 75-76 years). After a rough estimate of the perturbations the comet would sustain from the attraction of the planets, he predicted its return for 1757. Halley's prediction of the comet's return proved to be correct, although it was not seen until 25 December 1758 by Johann Georg Palitzsch, a German farmer and amateur astronomer, and did not pass through its perihelion until March 1759; the attraction of Jupiter and Saturn having caused a retardation of 618 days, as was computed by a team of three French mathematicians, Alexis Clairault, Joseph Lalande, and Nicole-Reine Lepaute, previously to its return. Halley did not live to see the comet's return, having died in 1742.

Related Topics:
1682 - 1531 - Petrus Apianus - 1607 - Johannes Kepler - Prague - 1757 - 25 December - 1758 - Johann Georg Palitzsch - Perihelion - 1759 - Jupiter - Saturn - French - Alexis Clairault - Joseph Lalande - Nicole-Reine Lepaute - 1742

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Halley's calculations enabled the comet's earlier appearances to be found in the historical record:

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• When the comet was observed in 1456, it passed very near to the Earth; its tail extended over 60° of the heavens and took the form of a sabre.
• In 1066, the comet was thought to be an omen: later that year Harold II of England died at the Battle of Hastings. It is shown on the Bayeux Tapestry, and the accounts which have been preserved represent it as having then appeared to be four times the size of Venus, and to have shone with a light equal to a fourth of that of the Moon.
• It is calculated that Comet Halley may have passed as close as 0.03 AU (3.2 million miles) from Earth in the year 837.
• Some have suggested that the comet's appearance in 12 BC might explain the Biblical story of the Star of Bethlehem. The artist Giotto di Bondone would have observed the comet in 1301 and his depiction of the Star of Bethlehem in the Nativity in the Arena Chapel cycle completed in 1305 is a candidate for an early depiction.
• Historical records show that Chinese astronomers observed the comet's appearance in 240 BC and possibly as early as 2467 BC. Observations of appearances after 240 BC are recorded by Chinese, Japanese, Babylonian and Islamic astronomers.