Prior to the 17th Century, the majority of people believed in alchemy, magic and witchcraft. This was when hardly anything was known about the actual mechanics of the Solar System, and until the invention of the telescope, people¹ thought that the Earth was fixed (didn't move), and all the heavenly bodies travelled around the Earth (geocentrism). It was also what the church preached, and anyone who dared to question doctrine were dealt with severely. Comets  – lumps of rock left over from the formation of the Solar System – rather spoiled the geocentric idea as it was obvious that they didn't follow the regular parade of stars. So they were denounced as signs from the devil, heralding evil intent, or at the very least, a bad omen.

Comet Halley

There are different kinds of comets: some are regular (periodic); others fly by never to be seen again. Comet Halley (1P/Halley) is a periodic comet; it revisits our area of space approximately every 76 years. It was named after English astronomer Edmond Halley (1656 - 1742), who worked out that well-recorded comets which had passed through the inner Solar System during 1531, 1607 and 1682 shared such similar orbits that he stated they were the same comet on return visits. He predicted the next time it would pass by for human observation and it did indeed return when Halley said it would, some 16 years after his death. A Memorial Plaque in the South Cloister of Westminster Abbey in London depicts the comet² which immortalised Edmond Halley.

Halley's Comet is scheduled to return for naked-eye viewing again in 2061, but astronomers can track the comet as it passes through the outer Solar System thanks to the VLT (Very Large Telescope). Its highly elliptical orbit takes it 35 AU³, so Halley's Comet flies out beyond the path of Neptune (30 AU) before heading back towards the Sun. The perihelion (closest approach to the Sun) is just 0.6 AU – the planet Venus' orbit is 0.7 AU.

Halley's Comet is a popular topic for writers and readers alike, and many non-fiction books have been written about the celestial visitor. Authors include Sir Patrick Moore, Isaac Asimov, Franklyn Mansfield Branley, Dennis B Fradin, Norman D Anderson, John Calvin Batchelor, Gregory Vogt, Edwin Emerson, Percy Seymour and George M Zwack.

Recorded Visits to the Inner Solar System by Halley's Comet

Modern day astronomers have tried to backtrack and calculate the dates when Halley's Comet visited previously. The most successful were Donald Yeomans at JPL in California, and Tao Kiang working in Ireland; in the early 1980s they managed to trace the comet back to 240 BC comparing historical records kept by ancient civilisations like the Babylonians and the Chinese.

• 240 BC, 164 BC, 87 BC, 11 BC
• 66 AD, 141, 218, 295, 374, 451, 530, 607, 684, 760, 837, 912, 989
• 1066, 1145, 1222, 1301, 1378, 1456, 1531, 1607, 1682, 1759, 1835, 1910, 1986

Future Visits

• 2061
• 2134 (this will be one of the swiftest revisits at 73 years. It will also be one of the closest⁴ approaches, at 0.0915 AU or 14m km/9m miles)

It is obvious the comet has no tail at all and the so-called tail must be the Sun rays which, while passing through the body of the comet, look like a tail. If the body of the comet is transparent and like the Earth has its two poles fairly flat and thus form a convex lens then everything on the Earth will be burnt provided the sunlight passes through the body of the comet and the focus falls on the surface of the Earth.
– Extract from a letter to the Royal Observatory, Greenwich, from Sze Zuk Chang Chin-liang of the Imperial Polytechnic College, Shanghai, after observing the comet in 1910 and worrying about the Earth being toasted during future visits.

In and Out with Halley's Comet

The earliest historical record of Comet Halley was made by Chinese astronomers (who thought comets were celestial ambassadors) in 240 BC: 'During this year a broom star (comet) was seen at the north direction and then at the west direction'. It was also recorded that the Empress Dowager died that summer. Babylonian skywatchers engraved a record of the next appearance of the comet in 164 BC on a cuneiform script tablet, which now resides in the British Museum. They also noted it in 87 BC, the same year that the Emperor of China, Han Wudi, died. This was also the first time an actual depiction of the comet was created; a coin featuring the comet on the crown of the Armenian king Tigranes II the Great (95 - 55 BC).

Some people have connected the revisit of 11 BC with the birth of Jesus Christ, but Biblical scholars say it was too early and therefore not the fabled Christmas Star. That year marked the exit of Octavia, the sister of the first Roman Emperor, Augustus, and wife of Mark Antony (who abandoned her for Queen Cleopatra VII of Egypt). The remarkable Octavia not only raised her own children following the desertion by her husband, but also adopted the children of Antony and Cleopatra after their suicides.

In 66 AD, the Roman elegantiae arbiter  (judge of elegance) Petronius committed suicide after being accused of treason. This year also saw the beginning of first Jewish-Roman War (The Great Revolt) which lasted seven years. During the comet's next appearance in 141, the Roman Empress Faustina (the Elder), wife of Antoninus Pius, died. She was well-loved and renowned for her charity work. Following her death aged about 40, her devastated husband pronounced her a goddess, set up an orphange for girls in her name, and began organising construction of a temple in her memory. In 218, Roman Emperor Marcus Opellius Macrinus was defeated in battle and executed following capture. His ten-year-old son, the new Emperor Diadumenianus, was also seized and put to the sword.

Born in the year 295 was Shi Hu, who grew up to become a tyrannical general who thought nothing of slaughtering the population of a captured city. He eventually became a feared Chinese emperor, doing away with two of his sons, their wives and children after relations broke down. A notable slaying committed in 374 was that of King Gabinius of the Germanic Quadi; the murderer was the Roman Marcellinus, son of Maximinus, the praefect of Gaul. A different Marcellinus, this one a saint and evangelist of Gaul, also died in 374. St Brigid of Kildare, an Irish patron saint, was born in 451; her Feast Day is celebrated on 1 February. The Battle of the Campus Mauriacus, between the Romans and their allies against Attila the Hun and his armies, took place in 451. With possibly 100,000 men on each side, the number of dead was estimated at 20,000 following the cessation of hostilities. Among the casualties of the battle was Theodoric, the king of the Visigoths.

During the comeback of the comet in the year 530, Pope Felix IV fell seriously ill and died. He had attempted to nominate his own successor, but his choice was overruled in the subsequent papal election, and Boniface II was elected instead. In 607, the year of the comet's next return, Apocrisarius George Hiltion was elected pope. He chose the papal name Boniface III, but after a couple of significant contributions to the post, he died the same year. In the year 684 the Japanese noted the great comet in their skies; its sighting was followed two months later by a massive earthquake which destroyed buildings such as homes and temples, and there was enormous loss of human and animal life. Ethælbert (or Æthelberht), king of East Anglia and joint ruler of England, died sometime during the year 760. Historians only know of his rule thanks to the discovery of a runic coin, said to be 42% silver. As this had been struck by Tiælred, a prolific minter of the time, it was deemed irrefutable evidence that Ethælbert had indeed existed. In 837, Drest mac Caustantin, who had ruled under the name of Drest IX of the Picts (now Scotland), died after just two years on the throne. This year marked Comet Halley's closest-ever approach (five million km) to the Earth; it was described by eyewitnesses as being 'as bright as Venus'.

By the time of the comet's visit in 912, Byzantine Emperor Leo VI had already outlived three wives who had failed to provide him with an heir. He married his mistress who gave him a son, but this marriage was not recognised by the church, so the child was deemed illegitimate. Leo VI declared his son co-emperor in the hope that he would inherit the title, but when Leo died in 912 aged 45 years, his son was only six and the throne passed to Leo's younger brother Alexander. A devastating earthquake in October 989 ruined the great dome of the Hagia Sophia in Constantinople (now Istanbul). The Armenian architect Trdat rebuilt it on the orders of the Byzantine Emperor Basil II. Repairs, which took six years altogether, began while the comet was still visible in the sky.

We know Comet Halley was around in 1066 because it appears on the famous Bayeux Tapestry depicting the Battle of Hastings along with the caption 'Isti Mirant Stella' (they marvel at the star). During the year 1144, Cardinal Gherardo Caccianemici dal Orso was elected Pope Lucius II, but he was killed after less than a year in office, coinciding with the comet's visit in 1145. Meanwhile, an English monk, Eadwine of Canterbury, must have taken time out from the transcribing he was working on because he drew an accurate portrayal of the comet on his Psalms manuscript.

The comet's return in 1222, when it was described as 'large as the half Moon... its colour was white but its rays were red', heralded the death of King John I of Sweden. King Andrew III of Hungary, 'the last golden twig of the Árpáds', died aged 35 in early 1301. The comet in the sky at the time inspired the Italian artist Giotto di Bondone's artistic rendition of the Star of Bethlehem on the famous painting The Adoration of the Magi. The subsequent return in 1378 coincided with the death of another pope, this time Gregory XI. Pope Calixtus III apparently excommunicated the comet when he saw it in 1456 because he believed it to be a prophet of impending doom. That year saw the passing of St John Capistran (Giovanni da Capistrano), also known as 'the soldier Saint', but Pope Calixtus III lived for another two years.

During the months of the 1531 revisit of Halley's Comet, the sadistic English interrogator and torturer of priests, Richard Topcliffe MP was born. The naval Battle of Gibraltar took place when the comet was next seen in the year 1607, but this was during the Dutch War of Independence (the Eighty Years' War). The entire Spanish fleet was destroyed, but of course this was good news for the Dutch people. One famous eyewitness of the 1607 apparition was Johannes Kepler (1571 - 1630). The year 1682 saw the commencement of the building of the Royal Hospital Chelsea for retired or injured British soldiers. Their distinctive scarlet uniforms make the 'Chelsea Pensioners' instantly recognisable at events like Remembrance Day parades. Halley himself saw the comet in 1682, inspiring him to research the history of it.

The next return was during 1759, when umpteen battles took place, as the world was slap bang in the middle of the Seven Years' War. This was the year that the Italian operatic composer Alessandro Stradella breathed his last, having survived an earlier assassination attempt by the hired henchmen of a rich and angry cuckolded Venetian. The Near East earthquake of 1759 saw the Ruins of Baalbek in Lebanon devastated; the ceiling of the Temple of Bacchus which inspired the decoration at Osterley Park, London, collapsed. The remains of Baalbek today includes the walls of the Temple of Bacchus and the 'stone of the south'. One good event to occur in 1759 was the founding of the Guinness⁵ Brewery in Dublin, Ireland.

French astronomer Charles Messier observed the comet in 1759. He became so obsessed with comets that King Louis XV of France nicknamed him the 'comet ferret'. Messier spent the rest of his life hunting them down, and in the meantime compiled a catalogue of 'non-comets' called Mémoires de l'Academie. This list contains some of the most fabulous things viewable from Earth, like star clusters, galaxies, nebulae and a supernova remnant. Some astronomers like to test themselves trying to locate all the Messier Objects within a certain timeframe, known as a 'Messier Marathon'. Also in the year 1759, preparations began for the necessary journeys around the world to witness the upcoming transit of Venus (in 1761). The transit had been forecast by Edmond Halley even though he knew he wouldn't live to see it himself, he planned the suitable venues for his adherents.

Unfortunately, several expeditions were scuppered due to the ongoing Seven Years' War and some of the best-laid plans never came to fruition. British astronomer Charles Mason (1730 - 86) and surveyor Jeremiah Dixon were sent to Sumatra by the Royal Society to view and record the transit. Their ship, the HMS Seahorse, was attacked by a French frigate and they had to return to Portsmouth. Their second voyage wouldn't have got them to Sumatra in time for the transit so they stopped at Cape Town, South Africa, as guests of the local governor and set up their equipment. Mason and Dixon obtained several accurate measurements of Venus' position on the solar disc, from what turned out to be the only successful observation made from the Southern Hemisphere.

I came in with Halley's Comet in 1835. It is coming again next year, and I expect to go out with it. It will be the greatest disappointment of my life if I don't go out with Halley's Comet. The Almighty has said, no doubt: 'Now here are these two unaccountable freaks; they came in together, they must go out together.'
from Mark Twain: A Biography by Albert Bigelow Pain (1912)

Comet Halley was visible in 1835 and 1910 – uncannily coinciding exactly with the birth and death of Mark Twain (the pseudonym of Samuel Clemens). The author predicted his own demise with obvious cosmic connections, although he wasn't the only person linked to the comet – the Italian astronomer Giovanni Virginio Schiaparelli shared exactly the same year of birth and death as Clemens. It was Schiaparelli who claimed to have discovered canali (canals) on Mars. He also studied comets and meteors, and was awarded the Royal Astronomical Society's Gold Medal in 1872. The asteroid 4062 Schiaparelli and the Martian crater Schiaparelli honour him.

The ancient Greeks called comets lampadias, which means 'burning torch'. In 1910 'Lady of the lamp' Florence Nightingale died while Halley's burning torch graced our skies. That same year the British King Edward VII expired. He had ruled for just nine years, having spent 60 years as Heir apparent⁶ while his mother Queen Victoria set a record for longest reigning British monarch. This time around the comet was captured on film for the first time, and 'comet fever' was all the rage. You could buy comet postcards and other souvenirs. Hawkers peddled anti-comet pills, as protection from noxious gases spewed by the comet's tail. Religious fanatics and prophets of doom forecast the end of the world. In the US, the Great Fire of 1910 raged in north-east Washington, north Idaho and west Montana, killing 86 people. Another fire, this time at the World Exhibition in Brussels, Belgium, destroyed the French and British exhibitions. Other world events in 1910: the Union of South Africa was created, and Portugal became a republic. Later in the 20th Century, the 'king of Rock'n'Roll' Elvis Presley made a personal appearance on the planet between showings of Halley's Comet. However, the legend was inducted into the Rock'n'Roll Hall of Fame by the two sons of another legend, Julian and Sean Lennon, during the time the comet was riding across the sky on 23 January, 1986. Fans needn't worry about the delay, it was the very first Induction dinner.

Christa's Vision

I have a vision of the world as a global village, a world without boundaries. Imagine a history teacher making history!
– Christa McAuliffe (1948 – 1986)

The doomed Space Shuttle  Challenger exploded just moments after taking off on 28 January, 1986. Part of the planned mission was to use the Spartan⁷ Halley short duration satellite to study ultraviolet light from the tail of Halley's Comet. The seven crew members killed included the first 'Teacher in Space', civilian Christa McAuliffe. Watching the launch and subsequent destruction were Christa's horrified parents, who had supported their daughter's application to join the NASA mission.

We will never forget them, nor the last time we saw them this morning as they prepared for their journey and waved goodbye, and slipped the surly bonds of Earth to touch the face of God.
– US President Ronald Reagan

Giotto Visits Halley's Comet

Europe's first deep space mission was named Giotto after the artist who painted the comet as the Star of Bethlehem, after its appearance in 1301. Spacecraft Giotto was sent to visit Comet Halley, passing as close as possible to the comet's nucleus, 596 km (370 miles), on 13 March, 1986. The comet was found to contain elements of hydrogen, carbon, nitrogen, oxygen, sodium, magnesium, silicon, calcium and iron in its chemical composition. The comet nucleus, measured at 16×7.5×8 km (10×4.7×5 miles), was emitting approximately 2,000 tonnes of dust and gas per minute. This debris provides us with the annual Orionid meteor shower, which peaks every October. Though not the best celestial fireworks event of the year, the show is dependable and regular enough to be nicknamed 'Old Faithful'.

The Giotto mission also supplied the very first image of a comet nucleus. Perhaps another space mission will be planned for the next return of Comet Halley during the middle of 2061. In the meantime we can but gaze at these remnants of the formation of our Solar System which are little more than dirty snowballs, and wonder where they've been, what they have seen, and who saw them before.

Halley's Comet in Science Fiction

With Comet Halley being the most famous comet in history, it has been the feature of many science fiction stories in print and on film. Just a few are detailed here:

Novels

• 2061: Odyssey Three by Arthur C Clarke

• Heart of the Comet by Gregory Benford and David Brin

TV and Film

• In 'Attack of the Cybermen', a 1985 episode of Doctor Who, the Cybermen plot to use Halley's Comet as a weapon to destroy the Earth.

• The animated series Futurama, set in the 30th Century, had two storylines about Halley's Comet.

• There is a museum containing an exhibit about Halley's Comet in the Griffith Observatory in Los Angeles, California. The Griffith Observatory, as well as dialogue about the comet, featured in the 'Future's End' episode of Star Trek: Voyager.

• There was an episode of The Time Tunnel called 'End of the World' in which the time travellers defused a potential riot by correctly predicting (because they had knowledge from the future) the exact instant at which the tail of Halley's Comet was going to extinguish.

• In 'Time's Arrow', a Star Trek: The Next Generation two-part story, the crew travel back in time and meet Samuel Clemens, who discovers who they are and subsequently gets beamed aboard the Enterprise. Making small talk with the gorgeous Ship's Counsellor Deanna Troi, he asks if the Enterprise crew have ever run into Halley's Comet.

• Cartoon favourite The Simpsons featured an episode where Homer said: 'This is the most exciting thing I've seen since Halley's Comet collided with the Moon'.

¹Although notably not Lucius Seneca, a Roman of the 1st Century AD, who wrote: 'Men will some day be able to demonstrate in what regions comets have their paths, why they move so far from the planets, what is their size and constitution'.²Several trailing tails from the comet plaque feature inscriptions of all Halley's achievements.³AU means Astronomical Unit, the average distance between the Sun and Earth, about 93 million miles or 150 million km.⁴Not the closest, which was just five million km in 837.⁵This important drink has become synonymous with the Emerald Isle and it even has its own h2g2 smiley: ⁶First in line for the throne.⁷Spartan stands for Shuttle Pointed Autonomous Research Tool for Astronomy.