Halley's Comet

For the video game, see Halley's Comet (video game).

1P/Halley (Halley's Comet)

Halley's Comet on 8 March 1986
Discovery
Discovered by	Prehistoric observation; Edmond Halley (recognition of periodicity)
Discovery date	1758 (first predicted perihelion)
Orbital characteristics[2]
Epoch 17 February 1994 (2449400.5)
Aphelion	35.082 AU
Perihelion	0.586 AU (last perihelion: 9 February 1986) (next perihelion: 28 July 2061)[1]
Semi-major axis	17.834 AU
Eccentricity	0.96714
Orbital period	75.32 yr
Mean anomaly	38.38°
Inclination	162.26°
Longitude of ascending node	58.42°
Argument of perihelion	111.33°
Earth MOID	0.0638 AU (9.54 million km)
Physical characteristics
Dimensions	7004150000000000000♠15 km × 8 km[3]
Mean diameter	7004110000000000000♠11 km[2]
Mass	7014220000000000000♠2.2×1014 kg[4]
Mean density	7002600000000000000♠0.6 g/cm3 (average)[5] 7002200000000000000♠0.2–1.5 g/cm3 (est.)[6]
Escape velocity	~0.002 km/s
Rotation period	2.2 d (52.8 h) (?)[7]
Albedo	0.04[8]
Apparent magnitude	28.2 (in 2003)[9]

Halley's Comet or Comet Halley, officially designated 1P/Halley,^[2] is a short-period comet visible from Earth every 75–76 years.^{[2][10][11][12]} Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and the only naked-eye comet that might appear twice in a human lifetime.^[13] Halley last appeared in the inner parts of the Solar System in 1986 and will next appear in mid-2061.^[14]

Halley's returns to the inner Solar System have been observed and recorded by astronomers since at least 240 BC. Clear records of the comet's appearances were made by Chinese, Babylonian, and medieval European chroniclers, but were not recognized as reappearances of the same object at the time. The comet's periodicity was first determined in 1705 by English astronomer Edmond Halley, after whom it is now named.

During its 1986 apparition, Halley's Comet became the first comet to be observed in detail by spacecraft, providing the first observational data on the structure of a comet nucleus and the mechanism of coma and tail formation.^[15][16] These observations supported a number of longstanding hypotheses about comet construction, particularly Fred Whipple's "dirty snowball" model, which correctly predicted that Halley would be composed of a mixture of volatile ices—such as water, carbon dioxide, and ammonia—and dust. The missions also provided data that substantially reformed and reconfigured these ideas; for instance, it is now understood that the surface of Halley is largely composed of dusty, non-volatile materials, and that only a small portion of it is icy.

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Contents

• 
  1 Pronunciation
  


• 
  2 Computation of orbit
  


• 
  3 Orbit and origin
  


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  4 Structure and composition
  


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  5 History
  
  
  
  • 
    5.1 Prior to 1066
    
  
  
  • 
    5.2 1066
    
  
  
  • 
    5.3 1145–1378
    
  
  
  • 
    5.4 1456
    
  
  
  • 
    5.5 1531–1835
    
  
  
  • 
    5.6 1910
    
  
  
  • 
    5.7 1986
    
  
  
  • 
    5.8 After 1986
    
  
  
  • 
    5.9 2061
    
  
  
  • 
    5.10 Apparitions
    
  
  
  
  


• 
  6 See also
  


• 
  7 References
  


• 
  8 Bibliography
  


• 
  9 External links
  

Pronunciation

Comet Halley is commonly pronounced /ˈhæli/, rhyming with valley, or /ˈheɪli/, rhyming with daily.^[17][18]Colin Ronan, one of Edmond Halley's biographers, preferred /ˈhɔːli/ (HAW-lee, similar to holly). Spellings of Halley's name during his lifetime included Hailey, Haley, Hayley, Halley, Hawley, and Hawly, so its contemporary pronunciation is uncertain, but contemporary individuals with this last name appear to prefer the version that rhymes with "valley".^[19]

Computation of orbit

Halley was the first comet to be recognized as periodic. Until the Renaissance, the philosophical consensus on the nature of comets, promoted by Aristotle, was that they were disturbances in Earth's atmosphere. This idea was disproved in 1577 by Tycho Brahe, who used parallax measurements to show that comets must lie beyond the Moon. Many were still unconvinced that comets orbited the Sun, and assumed instead that they must follow straight paths through the Solar System.^[20]

In 1687, Sir Isaac Newton published his Philosophiæ Naturalis Principia Mathematica, in which he outlined his laws of gravity and motion. His work on comets was decidedly incomplete. Although he had suspected that two comets that had appeared in succession in 1680 and 1681 were the same comet before and after passing behind the Sun (he was later found to be correct; see Newton's Comet),^[21] he was unable to completely reconcile comets into his model.

Ultimately, it was Newton's friend, editor and publisher, Edmond Halley, who, in his 1705 Synopsis of the Astronomy of Comets, used Newton's new laws to calculate the gravitational effects of Jupiter and Saturn on cometary orbits.^[22] Having compiled a list of 24 comet observations, he calculated that the orbital elements of a second comet that had appeared in 1682 were nearly the same as those of two comets that had appeared in 1531 (observed by Petrus Apianus) and 1607 (observed by Johannes Kepler).^[22][23] Halley thus concluded that all three comets were, in fact, the same object returning about every 76 years, a period that has since been found to vary between 74–79 years. After a rough estimate of the perturbations the comet would sustain from the gravitational attraction of the planets, he predicted its return for 1758.^[24] While he had personally observed the comet around perihelion in September 1682,^[25] Halley died in 1742 before he could observe its predicted return.^[26]

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. It did not pass through its perihelion until 13 March 1759, the attraction of Jupiter and Saturn having caused a retardation of 618 days.^[27] This effect was computed prior to its return (with a one-month error to 13 April)^[28] by a team of three French mathematicians, Alexis Clairaut, Joseph Lalande, and Nicole-Reine Lepaute.^[29] The confirmation of the comet's return was the first time anything other than planets had been shown to orbit the Sun. It was also one of the earliest successful tests of Newtonian physics, and a clear demonstration of its explanatory power.^[30] The comet was first named in Halley's honour by French astronomer Nicolas-Louis de Lacaille in 1759.^[30]

Some scholars have proposed that first-century Mesopotamian astronomers already had recognized Halley's Comet as periodic.^[31] This theory notes a passage in the Bavli Talmud^[32] that refers to "a star which appears once in seventy years that makes the captains of the ships err."^[33]

Researchers in 1981 attempting to calculate the past orbits of Halley by numerical integration starting from accurate observations in the seventeenth and eighteenth centuries could not produce accurate results further back than 837 due to a close approach to Earth in that year. It was necessary to use ancient Chinese comet observations to constrain their calculations.^[34]

Orbit and origin

The orbital path of Halley, against the orbits of Jupiter, Saturn, Uranus and Neptune.

Halley's orbital period has varied between 74–79 years since 240 BC.^[30][11] Its orbit around the Sun is highly elliptical, with an orbital eccentricity of 0.967 (with 0 being a circle and 1 being a parabolic trajectory). The perihelion, the point in the comet's orbit when it is nearest the Sun, is just 0.6 AU.^[35] This is between the orbits of Mercury and Venus. Its aphelion, or farthest distance from the Sun, is 35 AU (roughly the distance of Pluto). Unusual for an object in the Solar System, Halley's orbit is retrograde; it orbits the Sun in the opposite direction to the planets, or, clockwise from above the Sun's north pole. The orbit is inclined by 18° to the ecliptic, with much of it lying south of the ecliptic. (Because it is retrograde, the true inclination is 162°.)^[36] Due to the retrograde orbit, it has one of the highest velocities relative to the Earth of any object in the Solar System. The 1910 passage was at a relative velocity of 70.56 km/s (157,838 mph or 254,016 km/h).^[37] Because its orbit comes close to Earth's in two places, Halley is associated with two meteor showers: the Eta Aquariids in early May, and the Orionids in late October.^[38] Halley is the parent body to the Orionids. Observations conducted around the time of Halley's appearance in 1986 suggested that the comet could additionally perturb the Eta Aquariids meteor shower, although it might not be the parent of that shower.^[39]

Orionid meteor originating from Halley's Comet striking the sky below the Milky Way and to the right of Venus.

Halley is classified as a periodic or short-period comet; one with an orbit lasting 200 years or less.^[40] This contrasts it with long-period comets, whose orbits last for thousands of years. Periodic comets have an average inclination to the ecliptic of only ten degrees, and an orbital period of just 6.5 years, so Halley's orbit is atypical.^[30] Most short-period comets (those with orbital periods shorter than 20 years and inclinations of 20–30 degrees or less) are called Jupiter-family comets. Those resembling Halley, with orbital periods of between 20 and 200 years and inclinations extending from zero to more than 90 degrees, are called Halley-type comets.^[40][41] As of 2015^[update], only 75 Halley-type comets have been observed, compared with 511 identified Jupiter-family comets.^[42]

The orbits of the Halley-type comets suggest that they were originally long-period comets whose orbits were perturbed by the gravity of the giant planets and directed into the inner Solar System.^[40] If Halley was once a long-period comet, it is likely to have originated in the Oort cloud,^[41] a sphere of cometary bodies that has an inner edge of 20,000–50,000 AU. Conversely the Jupiter-family comets are generally believed to originate in the Kuiper belt,^[41] a flat disc of icy debris between 30 AU (Neptune's orbit) and 50 AU from the Sun (in the scattered disc). Another point of origin for the Halley-type comets was proposed in 2008, when a trans-Neptunian object with a retrograde orbit similar to Halley's was discovered, 2008 KV42, whose orbit takes it from just outside that of Uranus to twice the distance of Pluto. It may be a member of a new population of small Solar System bodies that serves as the source of Halley-type comets.^[43]

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.^[44] The non-gravitational effects can be crucial;^[44] as Halley approaches the Sun, it expels jets of sublimating gas from its surface, which knock it very slightly off its orbital path. These orbital changes cause delays in its perihelion of four days, average.^[45]

In 1989, Boris Chirikov and Vitaly Vecheslavov performed an analysis of 46 apparitions of Halley's Comet taken from historical records and computer simulations. These studies showed that its dynamics were chaotic and unpredictable on long timescales.^[46] Halley's projected lifetime could be as long as 10 million years. These studies also showed that many physical properties of Halley's Comet dynamics can be approximately described by a simple symplectic map, known as the Kepler map.^[47] More recent work suggests that Halley will evaporate, or split in two, within the next few tens of thousands of years, or will be ejected from the Solar System within a few hundred thousand years.^[48][41] Observations by D.W. Hughes suggest that Halley's nucleus has been reduced in mass by 80 to 90% over the last 2,000 to 3,000 revolutions.^[16]

Structure and composition

The nucleus of Halley's Comet, imaged by the Giotto probe in 1986. The dark coloration of the nucleus can be observed, as well as the jets of dust and gas erupting from its surface.

The Giotto and Vega missions gave planetary scientists their first view of Halley's surface and structure. Like all comets, as Halley nears the Sun, its volatile compounds (those with low boiling points, such as water, carbon monoxide, carbon dioxide and other ices) begin to sublime from the surface of its nucleus.^[49] This causes the comet to develop a coma, or atmosphere, up to 100,000 km across.^[3] Evaporation of this dirty ice releases dust particles, which travel with the gas away from the nucleus. Gas molecules in the coma absorb solar light and then re-radiate it at different wavelengths, a phenomenon known as fluorescence, whereas dust particles scatter the solar light. Both processes are responsible for making the coma visible.^[13] As a fraction of the gas molecules in the coma are ionized by the solar ultraviolet radiation,^[13] pressure from the solar wind, a stream of charged particles emitted by the Sun, pulls the coma's ions out into a long tail, which may extend more than 100 million kilometres into space.^[49][50] Changes in the flow of the solar wind can cause disconnection events, in which the tail completely breaks off from the nucleus.^[15]

Despite the vast size of its coma, Halley's nucleus is relatively small: barely 15 kilometres long, 8 kilometres wide and perhaps 8 kilometres thick.^[b] Its shape vaguely resembles that of a peanut.^[3] Its mass is relatively low (roughly 2.2 × 10¹⁴ kg)^[4] and its average density is about 0.6 g/cm³, indicating that it is made of a large number of small pieces, held together very loosely, forming a structure known as a rubble pile.^[5] Ground-based observations of coma brightness suggested that Halley's rotation period was about 7.4 days. Images taken by the various spacecraft, along with observations of the jets and shell, suggested a period of 52 hours.^[16] Given the irregular shape of the nucleus, Halley's rotation is likely to be complex.^[49] Although only 25% of Halley's surface was imaged in detail during the flyby missions, the images revealed an extremely varied topography, with hills, mountains, ridges, depressions, and at least one crater.^[16]

Halley is the most active of all the periodic comets, with others, such as Comet Encke and Comet Holmes, being one or two orders of magnitude less active.^[16] Its day side (the side facing the Sun) is far more active than the night side. Spacecraft observations showed that the gases ejected from the nucleus were 80% water vapour, 17% carbon monoxide and 3–4% carbon dioxide,^[51] with traces of hydrocarbons^[52] although more-recent sources give a value of 10% for carbon monoxide and also include traces of methane and ammonia.^[53] The dust particles were found to be primarily a mixture of carbon–hydrogen–oxygen–nitrogen (CHON) compounds common in the outer Solar System, and silicates, such as are found in terrestrial rocks.^[49] The dust particles decreased in size down to the limits of detection (~0.001 µm).^[15] The ratio of deuterium to hydrogen in the water released by Halley was initially thought to be similar to that found in Earth's ocean water, suggesting that Halley-type comets may have delivered water to Earth in the distant past. Subsequent observations showed Halley's deuterium ratio to be far higher than that found in Earth's oceans, making such comets unlikely sources for Earth's water.^[49]

Giotto provided the first evidence in support of Fred Whipple's "dirty snowball" hypothesis for comet construction; Whipple postulated that comets are icy objects warmed by the Sun as they approach the inner Solar System, causing ices on their surfaces to sublimate (change directly from a solid to a gas), and jets of volatile material to burst outward, creating the coma. Giotto showed that this model was broadly correct,^[49] though with modifications. Halley's albedo, for instance, is about 4%, meaning that it reflects only 4% of the sunlight hitting it; about what one would expect for coal.^[54] Thus, despite appearing brilliant white to observers on Earth, Halley's Comet is in fact pitch black. The surface temperature of evaporating "dirty ice" ranges from 170 K (−103 °C) at higher albedo to 220 K (−53 °C) at low albedo; Vega 1 found Halley's surface temperature to be in the range 300–400 K (27–127 °C). This suggested that only 10% of Halley's surface was active, and that large portions of it were coated in a layer of dark dust that retained heat.^[15] Together, these observations suggested that Halley was in fact predominantly composed of non-volatile materials, and thus more closely resembled a "snowy dirtball" than a "dirty snowball".^[16][55]

History

Prior to 1066

Observation of Halley's Comet, recorded in cuneiform on a clay tablet between 22 and 28 September 164 BC, Babylon, Iraq. British Museum
(BM 41462)

Halley may have been recorded as early as 467 BC, but this is uncertain. A comet was recorded in ancient Greece between 468 and 466 BC; its timing, location, duration, and associated meteor shower all suggest it was Halley.^[56] According to Pliny the Elder, that same year a meteorite fell in the town of Aegospotami, in Thrace. He described it as brown in colour and the size of a wagon load.^[57] Chinese chroniclers also mention a comet in that year.^[58]

Report of Halley's Comet by Chinese astronomers in 240 BC (Shiji)

The first certain appearance of Halley's Comet in the historical record is a description from 240 BC, in the Chinese chronicle Records of the Grand Historian or Shiji, which describes a comet that appeared in the east and moved north.^[59] The only surviving record of the 164 BC apparition is found on two fragmentary Babylonian tablets, now owned by the British Museum.^[59]

The apparition of 87 BC was recorded in Babylonian tablets which state that the comet was seen "day beyond day" for a month.^[60] This appearance may be recalled in the representation of Tigranes the Great, an Armenian king who is depicted on coins with a crown that features, according to Vahe Gurzadyan and R. Vardanyan, "a star with a curved tail [that] may represent the passage of Halley's Comet in 87 BC." Gurzadyan and Vardanyan argue that "Tigranes could have seen Halley's Comet when it passed closest to the Sun on August 6 in 87 BC" as the comet would have been a "most recordable event"; for ancient Armenians it could have heralded the New Era of the brilliant King of Kings.^[61]

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.^[10] It passed within 0.16 AU of Earth.^[62] According to the Roman historian Cassius Dio, a comet appeared suspended over Rome for several days portending the death of Marcus Vipsanius Agrippa in that year.^[63] Halley's appearance in 12 BC, only a few years distant from the conventionally assigned date of the birth of Jesus Christ, has led some theologians and astronomers to suggest that it might explain the biblical story of the Star of Bethlehem. There are other explanations for the phenomenon, such as planetary conjunctions, and there are also records of other comets that appeared closer to the date of Jesus' birth.^[64]

If, as has been suggested, the reference in the Talmud to "a star which appears once in seventy years that makes the captains of the ships err"^[65] (see above) refers to Halley's Comet, it may be a reference to the 66 AD appearance, because this passage is attributed to the Rabbi Yehoshua ben Hananiah. This apparition was the only one to occur during ben Hananiah's lifetime.^[66]

The 141 AD apparition was recorded in Chinese chronicles.^[67] It was also recorded in the Tamil work Purananuru, in connection with the death of the south Indian Chera king Yanaikatchai Mantaran Cheral Irumporai.^[68]

The 374 AD and 607 approaches each came within 0.09 AU of Earth.^[62] The 684 AD apparition was recorded in Europe in one of the sources used by the compiler of the 1493 Nuremberg Chronicles; it is the oldest-known picture of a comet. Chinese records also report it as the "broom star".^[69][23] The 451 AD apparition was said to herald the defeat of Attila the Hun at the Battle of Chalons.^[70]
In 837, Halley's Comet may have passed as close as 0.03 AU (3.2 million miles; 5.1 million kilometres) from Earth, by far its closest approach.^[62] Its tail may have stretched 60 degrees across the sky. It was recorded by astronomers in China, Japan, Germany, the Byzantine Empire, and the Middle East.^[10] In 912, Halley is recorded in the Annals of Ulster, which state "A dark and rainy year. A comet appeared."^[71]

1066

Halley's Comet in 1066 depicted in the Bayeux Tapestry

In 1066, the comet was seen in England and thought to be an omen: later that year Harold II of England died at the Battle of Hastings; it was a bad omen for Harold, but a good omen for the man who defeated him, William the Conqueror. The comet is represented on the Bayeux Tapestry and described in the tituli as a star. Surviving accounts from the period describe it as appearing to be four times the size of Venus and shining with a light equal to a quarter of that of the Moon. Halley came within 0.10 AU of Earth at that time.^[62]

This appearance of the comet is also noted in the Anglo-Saxon Chronicle. Eilmer of Malmesbury may have seen Halley previously in 989, as he wrote of it in 1066: "You've come, have you? ... You've come, you source of tears to many mothers, you evil. I hate you! It is long since I saw you; but as I see you now you are much more terrible, for I see you brandishing the downfall of my country. I hate you!"^[72]

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."^[71]Chaco Native Americans in New Mexico may have recorded the 1066 apparition in their petroglyphs.^[73]

1145–1378

The Adoration of the Magi (circa 1305) by Giotto, who purportedly modeled the star of Bethlehem on Halley, which had been sighted 4 years prior to this painting.

The 1145 apparition was recorded by the monk Eadwine. The 1986 apparition exhibited a fan tail similar to Eadwine's drawing.^[69] Some claim that Genghis Khan was inspired to turn his conquests toward Europe by the 1222 apparition.^[74] The 1301 apparition may have been seen by the artist Giotto di Bondone, who represented the Star of Bethlehem as a fire-colored comet in the Nativity section of his Arena Chapel cycle, completed in 1305.^[69] Its 1378 appearance is recorded in the Annales Mediolanenses^[75] as well as in East Asian sources.^[76]

1456

1456 comet in Zodiac

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 Lives of the Popes that,^[77]

A hairy and fiery star having then made its appearance for several days, the mathematicians declared that there would follow grievous pestilence, dearth and some great calamity. Calixtus, to avert the wrath of God, ordered supplications that if evils were impending for the human race He would turn all upon the Turks, the enemies of the Christian name. He likewise ordered, to move God by continual entreaty, that notice should be given by the bells to call the faithful at midday to aid by their prayers those engaged in battle with the Turk.

Platina's account is not mentioned in official records. In the 18th century, a Frenchman further embellished the story, in anger at the Church, by claiming that the Pope had "excommunicated" the comet, though this story was most likely his own invention.^[78]

Halley's apparition of 1456 was also witnessed in Kashmir and depicted in great detail by Śrīvara, a Sanskrit poet and biographer to the Sultans of Kashmir. He read the apparition as a cometary portent of doom foreshadowing the imminent fall of Sultan Zayn al-Abidin (AD 1418/1420–1470).^[79]

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.^[80]

1531–1835

Halley's periodic returns have been subject to scientific investigation since the 16th century. The three apparitions from 1531 to 1682 were noted by Edmond Halley, enabling him to predict its 1759 return.^[81] Streams of vapour observed during the comet's 1835 apparition prompted astronomer Friedrich Wilhelm Bessel to propose that the jet forces of evaporating material could be great enough to significantly alter a comet's orbit.^[82]

Illustrations of prior comet appearances
in a 1910 popular science publication

1682	1759	1835

1910

A photograph of Halley's Comet taken during its 1910 approach

The 1910 approach, which came into naked-eye view around 10 April^[62] and came to perihelion on 20 April,^[62] was notable for several reasons: it was the first approach of which photographs exist, and the first for which spectroscopic data were obtained.^[15] Furthermore, the comet made a relatively close approach of 0.15 AU,^[62] making it a spectacular sight. Indeed, on 19 May, Earth actually passed through the tail of the comet.^[83][84] One of the substances discovered in the tail by spectroscopic analysis was the toxic gas cyanogen,^[85] which led astronomer Camille Flammarion to claim that, when Earth passed through the tail, the gas "would impregnate the atmosphere and possibly snuff out all life on the planet."^[86] His pronouncement led to panicked buying of gas masks and quack "anti-comet pills" and "anti-comet umbrellas" by the public.^[87] In reality, as other astronomers were quick to point out, the gas is so diffuse that the world suffered no ill effects from the passage through the tail.^[86]

The comet added to the unrest in China on the eve of the Xinhai Revolution that would end the last dynasty in 1911. As James Hutson, a missionary in Sichuan Province at the time, recorded,

The people believe that it indicates calamity such as war, fire, pestilence, and a change of dynasty. In some places on certain days the doors were unopened for half a day, no water was carried and many did not even drink water as it was rumoured that pestilential vapour was being poured down upon the earth from the comet."^[88]

The 1910 visitation is also recorded as being the travelling companion of Hedley Churchward, the first known English Muslim to make the Haj pilgrimage to Mecca. However, his explanation of its scientific predictability did not meet with favour in the Holy City.^[89]

The comet was also fertile ground for hoaxes. One that reached major newspapers claimed that the Sacred Followers, a supposed Oklahoma religious group, attempted to sacrifice a virgin to ward off the impending disaster, but were stopped by the police.^[90]

American satirist and writer Mark Twain was born on 30 November 1835, exactly two weeks after the comet's perihelion. In his autobiography, published in 1909, he said,

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.'^[91][92]

Twain died on 21 April 1910, the day following the comet's subsequent perihelion.^[93] The 1985 fantasy film The Adventures of Mark Twain was inspired by the quotation.

Halley's 1910 apparition is distinct from the Great Daylight Comet of 1910, which surpassed Halley in brilliance and was actually visible in broad daylight for a short period, approximately four months before Halley made its appearance.^[94][95]

1986

Daily motion across sky during 1986 passage

Halley's Comet in 1986

1986 USSR miniature sheet, featuring Edmond Halley, Comet Halley, Vega 1, Vega 2, Giotto, Suisei (Planet-A)

Halley's 1986 apparition was the least favourable on record. The comet and Earth were on opposite sides of the Sun in February 1986, creating the worst viewing circumstances for Earth observers for the last 2,000 years.^[96] Halley's closest approach was 0.42 AU.^[97] Additionally, with increased light pollution from urbanization, many people failed to even see the comet. It was possible to observe it in areas outside of cities with the help of binoculars.^[98] Further, the comet appeared brightest when it was almost invisible from the northern hemisphere in March and April.^[99] Halley's approach was first detected by astronomers David Jewitt and G. Edward Danielson on 16 October 1982 using the 5.1 m Hale telescope at Mount Palomar and a CCD camera.^[100] The first person to visually observe the comet on its 1986 return was amateur astronomer Stephen James O'Meara on 24 January 1985. O'Meara used a home-built 24-inch telescope on top of Mauna Kea to detect the magnitude 19.6 comet.^[101] On 8 November 1985, Stephen Edberg (then serving as the Coordinator for Amateur Observations at NASA's Jet Propulsion Laboratory) and Charles Morris were the first to observe Halley's Comet with the naked eye in its 1986 apparition.^[102][103]

Although Halley's Comet's retrograde orbit and high inclination make it difficult to send a space probe to it,^[104] the 1986 apparition gave scientists the opportunity to closely study the comet, and several probes were launched to do so. The Soviet Vega 1 started returning images of Halley on 4 March 1986, and the first ever of its nucleus,^[16] and made its flyby on 6 March, followed by Vega 2 making its flyby on 9 March. On 14 March, the Giotto space probe, launched by the European Space Agency, made the closest pass of the comet's nucleus.^[16] There were also two Japanese probes, Suisei and Sakigake. The probes were unofficially known as the Halley Armada.^[105]

Based on data retrieved by Astron, the largest ultraviolet space telescope of the time, during its Halley's Comet observations in December 1985, a group of Soviet scientists developed a model of the comet's coma.^[106] The comet was also observed from space by the International Cometary Explorer (ICE). Originally International Sun-Earth Explorer 3, the probe was renamed and freed from its L₁ Lagrangian point location in Earth's orbit to intercept comets 21P/Giacobini-Zinner and Halley.^[107] ICE made its closest approach on March 28, 1986.

Two Space Shuttle missions—the ill-fated STS-51-L (ended by the Challenger disaster)^[108] and STS-61-E—were scheduled to observe Halley's Comet from low Earth orbit. STS-51-L carried the Shuttle-Pointed Tool for Astronomy (SPARTAN-203) satellite, also called the Halley's Comet Experiment Deployable (HCED).^[109] STS-61-E was a Columbia mission scheduled for March 1986, carrying the ASTRO-1 platform to study the comet.^[110] Due to the suspension of America's manned space program after the Challenger explosion, the mission was canceled, and ASTRO-1 would not fly until late 1990 on STS-35.^[111]

After 1986

Halley's Comet observed in 2003 at 28 AU from the Sun

On 12 February 1991, at a distance of 14.4 AU (2.15×10⁹ km) from the Sun, Halley displayed an outburst that lasted for several months, releasing a cloud of dust 300,000 km across.^[49] The outburst likely started in December 1990, and then the comet brightened from magnitude 24.3 to magnitude 18.9.^[112] Halley was most recently observed in 2003 by three of the Very Large Telescopes at Paranal, Chile, when Halley's magnitude was 28.2. The telescopes observed Halley, at the faintest and farthest any comet has ever been imaged, in order to verify a method for finding very faint trans-Neptunian objects.^[9] Astronomers are now able to observe the comet at any point in its orbit.^[9]

2061

The next predicted perihelion of Halley's Comet is 28 July 2061,^[1] when it is expected to be better positioned for observation than during the 1985–1986 apparition, as it will be on the same side of the Sun as Earth.^[11] It is expected to have an apparent magnitude of −0.3, compared with only +2.1 for the 1986 apparition.^[113] It has been calculated that on 9 September 2060, Halley will pass within 0.98 AU (147,000,000 km) of Jupiter, and then on 20 August 2061 will pass within 0.0543 AU (8,120,000 km) of Venus.^[114] In 2134, Halley is expected to pass within 0.09 AU (13,000,000 km) of Earth.^[114] Its apparent magnitude is expected to be −2.0.^[113]

Apparitions

Halley's calculations enabled the comet's earlier appearances to be found in the historical record. The following table sets out the astronomical designations for every apparition of Halley's Comet from 240 BC, the earliest documented widespread sighting.^[2][115] For example, "1P/1982 U1, 1986 III, 1982i" indicates that for the perihelion in 1986, Halley was the first period comet known (designated 1P) and this apparition was the first seen in half-month U (the second half of October)^[116] in 1982 (giving 1P/1982 U1); it was the third comet past perihelion in 1986 (1986 III); and it was the ninth comet spotted in 1982 (provisional designation 1982i). The perihelion dates of each apparition are shown.^[117] The perihelion dates farther from the present are approximate, mainly because of uncertainties in the modelling of non-gravitational effects. Perihelion dates of 1531 and earlier are in the Julian calendar, while perihelion dates 1607 and after are in the Gregorian calendar.^[118]

Halley's Comet is visible from Earth every 74–79 years.^[2][10][11]

Designation	Year BC/AD	Gap (years)	Date of perihelion	Visible duration	Closest approach	Description
1P/−239 K1, −239	240 BC	–	15 May	15 – 25 May		First confirmed sighting.
1P/−163 U1, −163	164 BC	76	20 May			Seen by Babylonians.
1P/−86 Q1, −86	87 BC	77	15 August	6 – 19 August		Seen by the Babylonians and Chinese.
1P/−11 Q1, −11	12 BC	75	8 October	August – 10 October	0.16 AU	Watched by Chinese for two months.
1P/66 B1, 66	66	78	26 January	25 – 26 January		May be the comet described in Josephus's The Jewish War as 'A comet of the kind called Xiphias, because their tails appear to represent the blade of a sword' that supposedly heralded the destruction of the Second Temple in 70 AD.[63]
1P/141 F1, 141	141	75	25 March	22 – 25 March		Described by the Chinese as bluish-white in colour. Described in Tamil literature and death of Chera (Yanaikatchai Mantaran Cheral Irumporai) king after appearance of comet.[119]
1P/218 H1, 218	218	77	6 April	6 April – 17 May		Described by the Roman historian Dion Cassius as 'a very fearful star' .
1P/295 J1, 295	295	77	7 April	7 – 20 April		Seen in China, but not spectacular.
1P/374 E1, 374	374	79	13 February	13 – 16 February	0.09 AU	Comet passed 13.5 million kilometres from Earth.
1P/451 L1, 451	451	77	3 July	28 June – 3 July		Appeared before the defeat of Attila the Hun at the Battle of Chalons.
1P/530 Q1, 530	530	79	15 November	27 September – 15 November		Noted in China and Europe, but not spectacular.
1P/607 H1, 607	607	77	26 March	15 – 26 March	0.09 AU	Comet passed 13.5 million kilometres from Earth.
1P/684 R1, 684	684	77	26 November	2 October – 26 November		First known Japanese records of the comet. Seen in Europe and depicted 800 years later in the Nuremberg Chronicle. Attempts have been made to connect an ancient Maya depiction of God L to the event.[120]
1P/760 K1, 760	760	76	10 June	20 May – 10 June		Seen in China, at the same time as another comet.
1P/837 F1, 837	837	77	25 February	25 – 28 February	0.03 AU	Closest-ever approach to the Earth (5 million km). Tail stretched halfway across the sky. Appeared as bright as Venus.
1P/912 J1, 912	912	75	27 July	18 – 27 July		Seen briefly in China and Japan.
1P/989 N1, 989	989	77	2 September	2 – 5 September		Seen in China, Japan, and (possibly) Korea.
1P/1066 G1, 1066	1066	77	25 March	January – 25 March	0.10 AU	Seen for over two months in China. Recorded in England and depicted on the later Bayeux tapestry which portrayed the events of that year.
1P/1145 G1, 1145	1145	79	19 April	15 – 19 April		Depicted on the Eadwine Psalter, with the remark that such 'hairy stars' appeared rarely, 'and then as a portent'.
1P/1222 R1, 1222	1222	77	10 September	10 – 28 September		Described by Japanese astronomers as being 'as large as the half Moon . . . Its colour was white but its rays were red'.
1P/1301 R1, 1301	1301	79	22 October	22 – 31 October		Seen by Giotto di Bondone and included in his painting The Adoration of the Magi. Chinese astronomers compared its brilliance to that of the first-magnitude star Procyon.
1P/1378 S1, 1378	1378	77	9 November	9 – 14 November		Passed within 10 degrees of the north celestial pole, more northerly than at any time during the past 2000 years. This is the last appearance of the comet for which Oriental records are better than Western ones.
1P/1456 K1, 1456	1456	78	8 January	8 January – 9 June		Observed in Italy by Paolo Toscanelli, who said its head was 'as large as the eye of an ox', with a tail 'fan-shaped like that of a peacock'. Arabs said the tail resembled a Turkish scimitar. Turkish forces attacked Belgrade.
1P/1531 P1, 1531	1531	75	26 August	26 August		Seen by Peter Apian, who noted that its tail always pointed away from the Sun. This sighting was included in Halley's table.
1P/1607 S1, 1607	1607	76	27 October	27 October		Seen by Johannes Kepler. This sighting was included in Halley's table.
1P/1682 Q1, 1682	1682	75	15 September	15 September		Seen by Edmond Halley at Islington.
1P/1758 Y1, 1759 I	1758	76	13 March	13 March – 25 December		Return predicted by Halley. First seen by Johann Palitzsch on 1758 December 25.
1P/1835 P1, 1835 III	1835	77	16 November	August – 16 November		First seen at the Vatican Observatory in August. Studied by John Herschel at the Cape of Good Hope.
1P/1909 R1, 1910 II, 1909c	1910	75	20 April	20 April – 20 May		Photographed for the first time. Earth passed through the comet's tail on 20 May.
1P/1982 U1, 1986 III, 1982i	1986	76	9 February	9 February	0.586 AU	Reached perihelion on 9 February, closest to Earth (63 million km) on 11 April. Nucleus photographed by the European space probe Giotto and the Russian probes Vega 1 and 2.
	2061	75	28 July	28 July 2061		Next return of Halley's comet.

See also

• 
  Astronomy portal
  

• List of Halley-type comets


• Halley's Comet in fiction

References

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107. 
     ^ P. Murdin (2000). "International Cometary Explorer (ICE)". Encyclopedia of Astronomy and Astrophysics. Institute of Physics Publishing. Bibcode:2000eaa..bookE4650.. doi:10.1888/0333750888/4650. ISBN 0-333-75088-8.
     


108. 
     ^ "STS-51L". NASA Kennedy Space Center. Retrieved 7 January 2010.
     


109. 
     ^ "Spartan 203 (Spartan Halley, HCED)". space.skyrocket.de. Retrieved 6 September 2011.
     


110. 
     ^ D. J. Shayler; C. Burgess (2007). "Ending of Eras". NASA's Scientist-Astronauts. Praxis. pp. 431–476. ISBN 0-387-21897-1. Retrieved 7 January 2009.
     


111. 
     ^ "STS-35 (38)". NASA. Retrieved 7 January 2010.
     


112. 
     ^ D. Prialnik; A. Bar-Nun (1992). "Crystallization of amorphous ice as the cause of Comet P/Halley's outburst at 14 AU". Astronomy and Astrophysics. 258 (2): L9–L12. Bibcode:1992A&A...258L...9P.
     


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     ^ ^ab S. Odenwald. "When will Halley's Comet return?". NASA. Archived from the original on 20 August 2011. Retrieved 29 November 2009.
     


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     ^ ^ab "JPL Close-Approach Data: 1P/Halley" (11 January 1994 last obs). Jet Propulsion Laboratory. Retrieved 5 May 2009.
     


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     ^ "Comet names and designations". International Comet Quarterly. Retrieved 20 January 2011.
     


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     ^ Richard M. Schmude (2010). Comets and How to Observe Them. Springer. p. 3. ISBN 978-1-4419-5790-0.
     


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     ^ The poet Kurunkozhiyur Kizhaar and Koodaloor Kizhaar who were present at the death of the king state that the death was portended by a falling star (possibly a comet) seven days previous to the occurrence.
     


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     ^ Star Gods of the Maya: Astronomy in Art, Folklore, and Calendars
     

Bibliography

• 
  Gore, Rick (December 1986). "Halley's Comet '86". National Geographic. Vol. 170 no. 6. pp. 758–785. ISSN 0027-9358. OCLC 643483454.
  


• 
  P. Lancaster-Brown (1985). Halley & His Comet. Blandford Press. ISBN 0-7137-1447-6.
  


• 
  C. Sagan; A. Druyan (1985). Comet. Random House. ISBN 0-394-54908-2.
  


• 
  Joseph Needham (1959). "Comets, meteors, and meteorites". Science and Civilisation in China: Volume 3, Mathematics and the Sciences of the Heavens and the Earth. Cambridge University Press. pp. 430–433. ISBN 978-0-521-05801-8.
  

External links

Wikimedia Commons has media related to Comet Halley.

• 
  Synopsis of the Astronomy of Comets (1706 reprint of Halley's 1705 paper)


• Halley's nucleus by Giotto spacecraft (ESA link)


• Image of Halley in 1986 by Giotto spacecraft (NASA link)


• cometography.com


• 1P/Halley at CometBase database


• seds.org


• 
  Orbital simulation from JPL (Java) / Ephemeris
  


• Donald Yeomans, "Great Comets in History"


• 
  A brief history of Halley's Comet (Ian Ridpath)


• Photographs of 1910 approach taken from the Lick Observatory from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections

v t e Comets
Features Nucleus Coma Tails Antitail Comet dust Meteor shower Types Periodic Numbered Lost Long period Halley-type Jupiter-family Encke-type Main-belt Non-periodic Near-parabolic Hyperbolic Unknown-orbit Great Comet Sungrazing (Kreutz) Extinct Rock Exocomet Interstellar Related Naming of comets Centaur Comet discoverers LINEAR Extraterrestrial atmosphere Oort cloud Small Solar System body Asteroid Exploration List of missions to comets List of comets visited by spacecraft Latest C/2018 C2 (Lemmon) C/2017 U7 1I/2017 U1 ʻOumuamua C/2016 U1 (NEOWISE) C/2015 G2 (MASTER) C/2015 F5 (SWAN-XingMing) C/2015 F3 C/2015 ER61 (PANSTARRS) C/2014 Q2 (Lovejoy) C/2014 E2 (Jacques) C/2013 US10 (Catalina) C/2013 A1 (Siding Spring) C/2012 S4 (PANSTARRS) C/2012 K1 (PANSTARRS) Culture and speculation Antimatter comet Comets in fiction list Comet vintages
Lists of comets (more) Periodic comets Until 1985 (all) 1P/Halley 2P/Encke 3D/Biela 4P/Faye 5D/Brorsen 6P/d'Arrest 7P/Pons–Winnecke 8P/Tuttle 9P/Tempel 10P/Tempel 11P/Tempel–Swift–LINEAR 12P/Pons–Brooks 13P/Olbers 14P/Wolf 15P/Finlay 16P/Brooks 17P/Holmes 18D/Perrine–Mrkos 19P/Borrelly 20D/Westphal 21P/Giacobini–Zinner 22P/Kopff 23P/Brorsen–Metcalf 24P/Schaumasse 25D/Neujmin 26P/Grigg–Skjellerup 27P/Crommelin 28P/Neujmin 29P/Schwassmann–Wachmann 30P/Reinmuth 31P/Schwassmann–Wachmann 32P/Comas Solà 33P/Daniel 34D/Gale 35P/Herschel–Rigollet 36P/Whipple 37P/Forbes 38P/Stephan–Oterma 39P/Oterma 40P/Väisälä 41P/Tuttle–Giacobini–Kresák 42P/Neujmin 43P/Wolf–Harrington 44P/Reinmuth 45P/Honda–Mrkos–Pajdušáková 46P/Wirtanen 47P/Ashbrook–Jackson 48P/Johnson 49P/Arend–Rigaux 50P/Arend 51P/Harrington 52P/Harrington–Abell 53P/Van Biesbroeck 54P/de Vico–Swift–NEAT 55P/Tempel–Tuttle 56P/Slaughter–Burnham 57P/du Toit–Neujmin–Delporte 58P/Jackson–Neujmin 59P/Kearns–Kwee 60P/Tsuchinshan 61P/Shajn–Schaldach 62P/Tsuchinshan 63P/Wild 64P/Swift–Gehrels 65P/Gunn 66P/du Toit 67P/Churyumov–Gerasimenko 68P/Klemola 69P/Taylor 70P/Kojima 71P/Clark 72P/Denning–Fujikawa 73P/Schwassmann–Wachmann 74P/Smirnova–Chernykh 75D/Kohoutek 76P/West–Kohoutek–Ikemura 77P/Longmore 78P/Gehrels 79P/du Toit–Hartley 80P/Peters–Hartley 81P/Wild 82P/Gehrels 83D/Russell 84P/Giclas 85D/Boethin 86P/Wild 87P/Bus 88P/Howell 89P/Russell 90P/Gehrels 91P/Russell 92P/Sanguin 93P/Lovas 94P/Russell 95P/Chiron 96P/Machholz 97P/Metcalf–Brewington 98P/Takamizawa 99P/Kowal 100P/Hartley 101P/Chernykh 102P/Shoemaker After 1985 (notable) 103P/Hartley 105P/Singer Brewster 107P/Wilson–Harrington 109P/Swift–Tuttle 111P/Helin–Roman–Crockett 114P/Wiseman–Skiff 128P/Shoemaker–Holt 139P/Väisälä–Oterma 144P/Kushida 147P/Kushida–Muramatsu 153P/Ikeya–Zhang 163P/NEAT 168P/Hergenrother 169P/NEAT 177P/Barnard 178P/Hug–Bell 205P/Giacobini 209P/LINEAR 238P/Read 246P/NEAT 252P/LINEAR 255P/Levy 273P/Pons–Gambart 276P/Vorobjov 289P/Blanpain 311P/PANSTARRS 322P/SOHO 332P/Ikeya-Murakami 354P/LINEAR 362P P/1997 B1 (Kobayashi) P/2010 B2 (WISE) P/2011 NO1 (Elenin) Comet-like asteroids 596 Scheila 2060 Chiron (95P) 4015 Wilson–Harrington (107P) 7968 Elst–Pizarro (133P) 165P/LINEAR 166P/NEAT 167P/CINEOS 60558 Echeclus (174P) 118401 LINEAR (176P) 238P/Read 259P/Garradd 311P/PANSTARRS 324P/La Sagra P/2010 A2 (LINEAR) P/2012 F5 (Gibbs) P/2012 T1 (PANSTARRS) P/2013 R3 (Catalina-PANSTARRS) (300163) 2006 VW139 Lost Recovered 11P/Tempel–Swift–LINEAR 15P/Finlay 17P/Holmes 27P/Crommelin 54P/de Vico–Swift–NEAT 55P/Tempel–Tuttle 57P/du Toit–Neujmin–Delporte 69P/Taylor 72P/Denning–Fujikawa 80P/Peters–Hartley 97P/Metcalf–Brewington 107P/Wilson–Harrington 109P/Swift–Tuttle 113P/Spitaler 122P/de Vico 157P/Tritton 177P/Barnard 205P/Giacobini 206P/Barnard–Boattini 271P/van Houten–Lemmon 273P/Pons–Gambart 289P/Blanpain Destroyed 3D/Biela 73P/Schwassmann–Wachmann D/1993 F2 (Shoemaker–Levy 9) Not found D/1770 L1 (Lexell) 5D/Brorsen 18D/Perrine–Mrkos 20D/Westphal 25D/Neujmin 34D/Gale 75D/Kohoutek 83D/Russell 85D/Boethin Visited by spacecraft 21P/Giacobini–Zinner (1985) 1P/Halley (1986) 26P/Grigg–Skjellerup (1992) 19P/Borrelly (2001) 81P/Wild (2004) 9P/Tempel (2005, 2011) C/2006 P1 (2007) 103P/Hartley (2010) 67P/Churyumov–Gerasimenko (2014) Non-Periodic comets (notable) Until 1910 C/-43 K1 (Caesar's Comet) X/1106 C1 (Great Comet of 1106) C/1577 V1 (Great Comet of 1577) C/1652 Y1 C/1680 V1 (Great Comet of 1680, Kirsch's Comet, Newton's Comet)) C/1702 H1 (Comet of 1702) C/1729 P1 (Comet of 1729, Comet Sarabat) C/1743 X1 (Great Comet of 1744, Comet Klinkenberg-Chéseaux) C/1760 A1 (Great Comet of 1760) C/1769 P1 (Great Comet of 1769) C/1807 R1 (Great Comet of 1807) C/1811 F1 (Great Comet of 1811) C/1819 N1 (Great Comet of 1819) C/1823 Y1 (Great Comet of 1823) C/1843 D1 (Great March Comet of 1843) C/1847 T1 (Miss Mitchell's Comet) C/1858 L1 (Comet Donati) C/1861 G1 (Comet Thatcher) C/1861 J1 (Great Comet of 1861) C/1865 B1 (Great Southern Comet of 1865) X/1872 X1 (Pogson's Comet) C/1874 H1 (Comet Coggia) C/1881 K1 (Comet Tebbutt) C/1882 R1 (Great Comet of 1882) C/1887 B1 (Great Southern Comet of 1887) C/1890 V1 (Comet Zona) C/1901 G1 (Great Comet of 1901) C/1910 A1 (Great January Comet of 1910) After 1910 C/1911 O1 (Brooks) C/1911 S3 (Beljawsky) C/1927 X1 (Skjellerup–Maristany) C/1931 P1 (Ryves) C/1941 B2 (de Kock-Paraskevopoulos) [de] C/1947 X1 (Southern Comet) [de] C/1948 V1 (Eclipse) C/1956 R1 (Arend–Roland) C/1957 P1 (Mrkos) [de] C/1961 O1 (Wilson-Hubbard) [de] C/1961 R1 (Humason) C/1962 C1 (Seki-Lines) [de] C/1963 R1 (Pereyra) C/1965 S1 (Ikeya-Seki) C/1969 Y1 (Bennett) C/1970 K1 (White–Ortiz–Bolelli) C/1973 E1 (Kohoutek) C/1975 V1 (West) C/1980 E1 (Bowell) C/1983 H1 (IRAS–Araki–Alcock) C/1989 X1 (Austin) C/1989 Y1 (Skorichenko–George) C/1992 J1 (Spacewatch–Rabinowitz) C/1993 Y1 (McNaught–Russell) C/1995 O1 (Hale–Bopp) C/1996 B2 (Hyakutake) C/1997 L1 (Zhu–Balam) C/1998 H1 (Stonehouse) C/1998 J1 (SOHO) C/1999 F1 (Catalina) C/1999 S4 (LINEAR) C/2000 U5 (LINEAR) C/2000 W1 (Utsunomiya-Jones) C/2001 OG108 (LONEOS) C/2001 Q4 (NEAT) C/2002 T7 (LINEAR) C/2004 F4 (Bradfield) [de] C/2004 Q2 (Machholz) C/2006 A1 (Pojmański) C/2006 M4 (SWAN) C/2006 P1 (McNaught) C/2007 E2 (Lovejoy) C/2007 F1 (LONEOS) C/2007 K5 (Lovejoy) C/2007 N3 (Lulin) C/2007 Q3 (Siding Spring) C/2007 W1 (Boattini) C/2008 Q1 (Matičič) C/2009 F6 (Yi–SWAN) C/2009 R1 (McNaught) C/2010 X1 (Elenin) C/2011 L4 (PANSTARRS) C/2011 W3 (Lovejoy) C/2012 E2 (SWAN) C/2012 F6 (Lemmon) C/2012 K1 (PANSTARRS) C/2012 S1 (ISON) C/2012 S4 (PANSTARRS) C/2013 A1 (Siding Spring) C/2013 R1 (Lovejoy) C/2013 US10 (Catalina) C/2013 V5 (Oukaimeden) C/2014 E2 (Jacques) C/2014 Q2 (Lovejoy) C/2015 ER61 (PANSTARRS) C/2015 V2 (Johnson) 1I/2017 U1 ʻOumuamua C/2017 U7 C/2018 C2 (Lemmon) After 1910 (by name) Arend–Roland Austin Beljawsky Bennett Boattini Bowell Bradfield [de] Brooks Catalina C/1999 F1 C/2013 US10 de Kock–Paraskevopoulos [de] Eclipse Elenin Hale-Bopp Humason Hyakutake Ikeya-Seki IRAS–Araki–Alcock ISON Jacques Johnson Kohoutek Lemmon C/2012 F6 C/2018 C2 LINEAR C/1999 S4 C/2000 U5 C/2002 T7 LONEOS C/2001 OG108 C/2007 F1 Lovejoy C/2007 E2 C/2007 K5 C/2011 W3 C/2013 R1 C/2014 Q2 Lulin Machholz Matičič McNaught C/2006 P1 C/2009 R1 McNaught–Russell Mrkos [de] NEAT Oukaimeden ʻOumuamua Pan-STARRS C/2011 L4 C/2012 K1 C/2012 S4 311P C/2015 ER61 Pereyra Pojmański Ryves Seki–Lines [de] Siding Spring C/2007 Q3 C/2013 A1 Skjellerup–Maristany Skorichenko–George SOHO Southern [de] Spacewatch–Rabinowitz Stonehouse SWAN C/2006 M4 C/2012 E2 Utsunomiya–Jones West White–Ortiz–Bolelli Wilson–Hubbard [de] Yi–SWAN Zhu–Balam
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