Halley’s Comet has visited us three times, in 1835, 1910, and in 1985–86. Historical records show that the Comet’s previous appearances stretch back long before comets were recognized to be periodic. Halley’s comet has been sighted on 30 occasions, the earliest recorded sighting by the Chinese in 240 BC.
To chase the orbit of a comet back through time is not easy for the gravitational effect of the planets are always moving the comet and changing its orbit. If the comet’s orbit is slightly expanded by the pull of the planets, it will take longer to return; if the orbit shrinks, the comet will come back sooner.
The best observations of Halley’s Comet come from China. For over 2000 years, the Chinese government ran an astronomical bureau. Their records are a source of information about ancient events in the sky.
Of the present-day astronomers who have tried backtracking Halley’s Comet, the most successful have been Donald Yeomans, who used NASA’s computers at the Jet Propulsion Laboratory in California, and Tao Kiang, a Chinese astronomer based at Dunsink Observatory in Ireland. In their research, published in 1981, Yeomans and Kiang calculated that the Comet made an exceptionally close approach to the Earth in AD 837. There are extensive descriptions of this spectacular ‘broom star’ from China: ‘on the night of April 9 its length was more than 50 degrees. It branched into two tails.
Yeomans and Kiang found that the earliest reliable record of Halley’s Comet was in 240 BC, when a Chinese source briefly noted: 'During this year a broom star was seen at the north direction and then at the west direction'.
Surprisingly, the Chinese did not record the Comet’s subsequent appearance in 164 BC, and only vaguely mentioned it in 87 BC. This was a drawback for Yeomans and Kiang, who needed to check their calculations for those years. But confirmation came from a different direction: the Babylonians, inhabitants of the Middle East, who carefully compiled diaries of astronomical information.
Their records for 164 BC and 87 BC contain unmistakable references to a comet that can only be Halley’s Comet putting in its regular appearances according to the schedule established by Yeomans and Kiang.
More recently, we know that it was Halley’s comet in 1066 spelled doom for King Harold at the Battle of Hastings. Its depiction on the Bayeux Tapestry, being pointed out to King Harold by his worried followers, is perhaps the most famous image of a comet in history. An earlier appearance of Halley’s comet, in AD 684, is pictured in the Nuremberg Chronicle.
Eadwine, a Canterbury monk, sketched the Comet at its 1145 appearance on the bottom of an illuminated manuscript of Psalms he was writing. Among those who looked at the Comet on its appearance in 1301 was the Italian artist Giotto di Bondone who painted it as the Star of Bethlehem, darting golden fires in the background of his fresco of The Adoration of the Magi. ☄
To chase the orbit of a comet back through time is not easy for the gravitational effect of the planets are always moving the comet and changing its orbit. If the comet’s orbit is slightly expanded by the pull of the planets, it will take longer to return; if the orbit shrinks, the comet will come back sooner.
The best observations of Halley’s Comet come from China. For over 2000 years, the Chinese government ran an astronomical bureau. Their records are a source of information about ancient events in the sky.
Of the present-day astronomers who have tried backtracking Halley’s Comet, the most successful have been Donald Yeomans, who used NASA’s computers at the Jet Propulsion Laboratory in California, and Tao Kiang, a Chinese astronomer based at Dunsink Observatory in Ireland. In their research, published in 1981, Yeomans and Kiang calculated that the Comet made an exceptionally close approach to the Earth in AD 837. There are extensive descriptions of this spectacular ‘broom star’ from China: ‘on the night of April 9 its length was more than 50 degrees. It branched into two tails.
Yeomans and Kiang found that the earliest reliable record of Halley’s Comet was in 240 BC, when a Chinese source briefly noted: 'During this year a broom star was seen at the north direction and then at the west direction'.
Surprisingly, the Chinese did not record the Comet’s subsequent appearance in 164 BC, and only vaguely mentioned it in 87 BC. This was a drawback for Yeomans and Kiang, who needed to check their calculations for those years. But confirmation came from a different direction: the Babylonians, inhabitants of the Middle East, who carefully compiled diaries of astronomical information.
Their records for 164 BC and 87 BC contain unmistakable references to a comet that can only be Halley’s Comet putting in its regular appearances according to the schedule established by Yeomans and Kiang.
More recently, we know that it was Halley’s comet in 1066 spelled doom for King Harold at the Battle of Hastings. Its depiction on the Bayeux Tapestry, being pointed out to King Harold by his worried followers, is perhaps the most famous image of a comet in history. An earlier appearance of Halley’s comet, in AD 684, is pictured in the Nuremberg Chronicle.
Eadwine, a Canterbury monk, sketched the Comet at its 1145 appearance on the bottom of an illuminated manuscript of Psalms he was writing. Among those who looked at the Comet on its appearance in 1301 was the Italian artist Giotto di Bondone who painted it as the Star of Bethlehem, darting golden fires in the background of his fresco of The Adoration of the Magi. ☄