Halley's Comet or Comet Halley, officially designated 1P/Halley, is a
short-period comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are ...
visible from
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
every 75–79 years.
Halley is the only known short-period
comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...
that is regularly visible to the
naked eye
Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to normal ...
from Earth, and thus the only naked-eye comet that can appear twice in a human lifetime.
Halley last appeared in the inner parts of the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
in 1986 and will next appear in mid-2061.
Halley's periodic returns to the
inner Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
have been observed and recorded by astronomers around the world since at least 240 BC. But it was not until 1705 that the English astronomer
Edmond Halley understood that these appearances were reappearances of the same comet. As a result of this discovery, the comet is named after Halley.
During its 1986 visit to the inner Solar System, Halley's Comet became the first comet to be observed in detail by
spacecraft
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...
, providing the first observational data on the structure of a
comet nucleus and the mechanism of
coma
A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...
and
tail
The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...
formation.
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
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
,
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
,
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
, and
dust
Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...
. 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.
Pronunciation
Comet Halley is commonly pronounced , rhyming with ''valley'', or , rhyming with ''daily''.
Colin Ronan
Colin Alistair Ronan FRAS (4 June 1920, in London – 1 June 1995) was a British author and specialist in the history and philosophy of science.
Education
Colin Alistair Ronan was educated at Abingdon School in Abingdon-on-Thames, Oxfordshire f ...
, one of
Edmond Halley's biographers, preferred , rhyming with ''crawly''. Spellings of Halley's name during his lifetime included ''Hailey, Haley, Hayley, Halley, Hawley'', and ''Hawly'', so its contemporary pronunciation is uncertain, but current bearers of this surname appear to prefer the version that rhymes with "valley".
Computation of orbit
![Halley's Comet animation](https://upload.wikimedia.org/wikipedia/commons/5/51/Halley%27s_Comet_animation.gif)
Halley was the first comet to be recognized as periodic. Until the
Renaissance
The Renaissance ( , ) , from , with the same meanings. is a period in European history marking the transition from the Middle Ages to modernity and covering the 15th and 16th centuries, characterized by an effort to revive and surpass ideas ...
, the philosophical consensus on the nature of comets, promoted by
Aristotle
Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher and polymath during the Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatetic school of phil ...
, was that they were disturbances in Earth's atmosphere. This idea was disproved in 1577 by
Tycho Brahe, who used
parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...
measurements to show that comets must lie beyond the
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
. Many were still unconvinced that comets orbited the Sun, and assumed instead that they must follow straight paths through the Solar System.
[Lancaster-Brown, Peter; ''Halley & His Comet'', pp. 14, 25]
In 1687,
Sir Isaac Newton published his ''
Philosophiæ Naturalis Principia Mathematica
(English: ''Mathematical Principles of Natural Philosophy'') often referred to as simply the (), is a book by Isaac Newton that expounds Newton's laws of motion and his law of universal gravitation. The ''Principia'' is written in Latin and ...
'', in which he outlined his laws of
gravity
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
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), 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.
[Lancaster-Brown, Peter; ''Halley & His Comet'', p. 76] Having compiled a list of 24 comet observations, he calculated that the
orbital elements
Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are considered in two-body systems using a Kepler orbit. There are many different ways to mathematically describe the same ...
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
Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and writer on music. He is a key figure in the 17th-century Scientific Revolution, best known for his laws ...
).
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 and 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. While he had personally observed the comet around
perihelion in September 1682,
Halley died in 1742 before he could observe its predicted return.
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
Johann Georg Palitzsch (11 June 1723 – 21 February 1788) was a German astronomer who became famous for recovering Comet 1P/Halley (better known as Halley's Comet) on Christmas Day, 1758.Hoffmann, Christian Gotthold (1759 January 20) "Nach ...
, a German farmer and amateur astronomer. It did not pass through its
perihelion until 13 March 1759, the attraction of
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...
and
Saturn
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
having caused a retardation of 618 days. This effect was computed before its return (with a one-month error to 13 April) by a team of three French mathematicians,
Alexis Clairaut,
Joseph Lalande
Joseph is a common male given name, derived from the Hebrew Yosef (יוֹסֵף). "Joseph" is used, along with "Josef", mostly in English, French and partially German languages. This spelling is also found as a variant in the languages of the mo ...
, and
Nicole-Reine Lepaute. 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.
The comet was first named in Halley's honour by French astronomer
Nicolas-Louis de Lacaille
Abbé Nicolas-Louis de Lacaille (; 15 March 171321 March 1762), formerly sometimes spelled de la Caille, was a kingdom of France, French astronomer and geodesist who named 14 out of the IAU designated constellations, 88 constellations. From 1750 ...
in 1759.
Some scholars have proposed that first-century
Mesopotamia
Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the F ...
n astronomers already had recognized Halley's Comet as periodic. This theory notes a passage in the Babylonian
Talmud
The Talmud (; he, , Talmūḏ) is the central text of Rabbinic Judaism and the primary source of Jewish religious law (''halakha'') and Jewish theology. Until the advent of modernity, in nearly all Jewish communities, the Talmud was the cente ...
, tractate
Horayot that refers to "a star which appears once in seventy years that makes the captains of the ships err."
Researchers in 1981 attempting to calculate the past orbits of Halley by
numerical integration
In analysis, numerical integration comprises a broad family of algorithms for calculating the numerical value of a definite integral, and by extension, the term is also sometimes used to describe the numerical solution of differential equations ...
starting from accurate observations in the seventeenth and eighteenth centuries could not produce accurate results further back than 837 owing to a close approach to Earth in that year. It was necessary to use
ancient Chinese comet observations to constrain their calculations.
Orbit and origin
Halley's orbital period has varied between 74 and 79 years since 240 BC.
Its orbit around the
Sun is highly
elliptical
Elliptical may mean:
* having the shape of an ellipse, or more broadly, any oval shape
** in botany, having an elliptic leaf shape
** of aircraft wings, having an elliptical planform
* characterised by ellipsis (the omission of words), or by conc ...
, with an
orbital eccentricity
In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values betwee ...
of 0.967 (with 0 being a circle and 1 being a
parabolic trajectory
In astrodynamics or celestial mechanics a parabolic trajectory is a Kepler orbit with the eccentricity equal to 1 and is an unbound orbit that is exactly on the border between elliptical and hyperbolic. When moving away from the source it is ca ...
). The perihelion, the point in the comet's orbit when it is nearest the Sun, is . This is between the orbits of
Mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
and
Venus
Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...
. Its
aphelion, or farthest distance from the Sun, is (roughly the distance of
Pluto
Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...
). 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°.) Owing to the retrograde orbit, it has one of the highest velocities relative to the
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
of any object in the Solar System. The 1910 passage was at a
relative velocity of .
Because its orbit comes close to Earth's in two places, Halley is associated with two
meteor shower
A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extre ...
s: the
Eta Aquariids in early May, and the
Orionids The Orionids meteor shower, often shortened to the Orionids, is the most prolific meteor shower associated with Halley's Comet. The Orionids are so-called because the point they appear to come from, called the radiant, lies in the constellation O ...
in late October. Halley is the parent body to the Orionids, while observations conducted around the time of Halley's appearance in 1986 suggested that the comet could additionally perturb the Eta Aquariids, although it might not be the parent of that shower.
![Orionid12n](https://upload.wikimedia.org/wikipedia/commons/a/ab/Orionid12n.jpg)
Halley is classified as a ''periodic'' or ''short-period
comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...
''; one with an orbit lasting 200 years or less.
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.
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.
[
] , only 75 Halley-type comets have been observed, compared with 511 identified Jupiter-family comets.
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.
If Halley was once a long-period comet, it is likely to have originated in the
Oort cloud,
a sphere of cometary bodies around
20,000–50,000 au from the Sun. Conversely the Jupiter-family comets are generally believed to originate in the
Kuiper belt
The Kuiper belt () is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...
,
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, , 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.
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 non-gravitational effects can be crucial;
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 on average.
In 1989,
Boris Chirikov
Boris Valerianovich Chirikov (russian: Борис Валерианович Чириков; 6 June 1928 – 12 February 2008) was a Soviet and Russian physicist.
He was the founder of the physical theory of Hamiltonian chaos and made pione ...
and Vitold 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. 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. 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.
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.
Structure and composition
The ''
Giotto
Giotto di Bondone (; – January 8, 1337), known mononymously as Giotto ( , ) and Latinised as Giottus, was an Italian painter and architect from Florence during the Late Middle Ages. He worked during the Gothic/Proto-Renaissance period. Giot ...
'' and ''
Vega
Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, an ...
'' 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
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
,
carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
,
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
and other
ices) begin to
sublimate from the surface of its
nucleus
Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to:
*Atomic nucleus, the very dense central region of an atom
*Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA
Nucle ...
.
This causes the comet to develop a
coma
A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...
, or atmosphere, up to 100,000 km across.
Evaporation of this dirty ice releases
dust
Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...
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
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
, whereas dust particles
scatter the solar light. Both processes are responsible for making the coma visible.
As a fraction of the gas molecules in the coma are
ionized by the solar
ultraviolet radiation,
pressure from the
solar wind, a stream of charged particles emitted by the Sun, pulls the coma's ions out into a long
tail
The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...
, which may extend more than 100 million kilometres into space.
Changes in the flow of the solar wind can cause
disconnection events, in which the tail completely breaks off from the nucleus.
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. Its shape vaguely resembles that of a
peanut shell.
Its mass is relatively low (roughly 2.2 kg)
and its average density is about 0.6 g/cm
3, indicating that it is made of a large number of small pieces, held together very loosely, forming a structure known as a
rubble pile.
Ground-based observations of coma brightness suggested that Halley's
rotation period
The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...
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.
Given the irregular shape of the nucleus, Halley's rotation is likely to be complex.
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.
Halley is the most active of all the periodic comets, with others, such as
Comet Encke and
Comet Holmes
Comet Holmes (official designation: 17P/Holmes) is a periodic comet in the Solar System, discovered by the British amateur astronomer Edwin Holmes on November 6, 1892. Although normally a very faint object, Holmes became notable during its Octo ...
, being one or two
orders of magnitude less active.
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, with traces of hydrocarbons although more-recent sources give a value of 10% for carbon monoxide and also include traces of
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
and
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
. 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.
The dust particles decreased in size down to the limits of detection (≈0.001 µm).
The ratio of
deuterium
Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two Stable isotope ratio, stable isotopes of hydrogen (the other being Hydrogen atom, protium, or hydrogen-1). The atomic nucleus, nucleus of a deuterium ato ...
to
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
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.
''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,
though with modifications. Halley's
albedo
Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...
, for instance, is about 4%, meaning that it reflects only 4% of the sunlight hitting it; about what one would expect for coal. 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 at higher albedo to at low albedo;
Vega 1 found Halley's surface temperature to be in the range . 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.
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".
History
Before 1066
![Babylonian tablet recording Halley's comet](https://upload.wikimedia.org/wikipedia/commons/3/38/Babylonian_tablet_recording_Halley%27s_comet.jpg)
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. According to
Pliny the Elder
Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic '' ...
, that same year a meteorite fell in the town of
Aegospotami
Aegospotami ( grc, Αἰγὸς Ποταμοί, ''Aigos Potamoi'') or AegospotamosMish, Frederick C., Editor in Chief. “Aegospotami.” '' Webster’s Ninth New Collegiate Dictionary''. 9th ed. Springfield, MA: Merriam-Webster Inc., 1985. , (in ...
, in
Thrace
Thrace (; el, Θράκη, Thráki; bg, Тракия, Trakiya; tr, Trakya) or Thrake is a geographical and historical region in Southeast Europe, now split among Bulgaria, Greece, and Turkey, which is bounded by the Balkan Mountains to t ...
. He described it as brown in colour and the size of a wagon load. Chinese chroniclers also mention a comet in that year.
![Chinese report of Halley's Comet apparition in 240 BC from the Shiji (史記)](https://upload.wikimedia.org/wikipedia/commons/c/c0/Chinese_report_of_Halley%27s_Comet_apparition_in_240_BC_from_the_Shiji_%28%E5%8F%B2%E8%A8%98%29.jpg)
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
''Records of the Grand Historian'', also known by its Chinese name ''Shiji'', is a monumental history of China that is the first of China's 24 dynastic histories. The ''Records'' was written in the early 1st century by the ancient Chinese hist ...
'' or ''Shiji'', which describes a comet that appeared in the east and moved north.
The only surviving record of the 164 BC apparition is found on two fragmentary Babylonian tablets, now owned by the
British Museum
The British Museum is a public museum dedicated to human history, art and culture located in the Bloomsbury area of London. Its permanent collection of eight million works is among the largest and most comprehensive in existence. It docum ...
.
The apparition of 87 BC was recorded in Babylonian tablets which state that the comet was seen "day beyond day" for a month. This appearance may be recalled in the representation of
Tigranes the Great, an
Armenia
Armenia (), , group=pron officially the Republic of Armenia,, is a landlocked country in the Armenian Highlands of Western Asia.The UNbr>classification of world regions places Armenia in Western Asia; the CIA World Factbook , , and ''Ox ...
n king who is depicted on coins with a crown that features, according to
Vahe Gurzadyan and R. Vardanyan, "a star with a curved tail
hatmay 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.
The apparition of 12 BC was recorded in the ''
Book of Han'' by
Chinese astronomers
Astronomy in China has a long history stretching from the Shang dynasty, being refined over a period of more than 3,000 years. The Ancient China, ancient Chinese people have identified stars from 1300 BCE, as Chinese star names later categoriz ...
of the
Han Dynasty
The Han dynasty (, ; ) was an imperial dynasty of China (202 BC – 9 AD, 25–220 AD), established by Liu Bang (Emperor Gao) and ruled by the House of Liu. The dynasty was preceded by the short-lived Qin dynasty (221–207 BC) and a warr ...
who tracked it from August through October.
It passed within 0.16 au of Earth.
According to the Roman historian
Cassius Dio
Lucius Cassius Dio (), also known as Dio Cassius ( ), was a Roman historian and senator of maternal Greek origin. He published 80 volumes of the history on ancient Rome, beginning with the arrival of Aeneas in Italy. The volumes documented the ...
, a comet appeared suspended over Rome for several days portending the death of
Marcus Vipsanius Agrippa
Marcus Vipsanius Agrippa (; BC – 12 BC) was a Roman general, statesman, and architect who was a close friend, son-in-law, and lieutenant to the Roman emperor Augustus. He was responsible for the construction of some of the most notable buildi ...
in that year.
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
theologian
Theology is the systematic study of the nature of the divine and, more broadly, of religious belief. It is taught as an academic discipline, typically in universities and seminaries. It occupies itself with the unique content of analyzing the ...
s 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 conjunction
In astronomy, a conjunction occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude, usually as observed from Earth.
When two objects always appear close to the ecliptic—such as two ...
s, and there are also records of other comets that appeared closer to the date of Jesus' birth.
![Paris1337_Horayot_10a](https://upload.wikimedia.org/wikipedia/commons/c/c5/Paris1337_Horayot_10a.png)
If, as has been suggested, the reference by
Yehoshua ben Hananiah in
b. Horayot 10a to "a star which arises once in seventy years and misleads the sailors" refers to Halley's Comet, it may be a reference to the 66 AD appearance, because this apparition was the only one to occur during Yehoshua ben Hananiah's lifetime.
The 141 AD apparition was recorded in Chinese chronicles. It was also recorded in the
Tamil
Tamil may refer to:
* Tamils, an ethnic group native to India and some other parts of Asia
** Sri Lankan Tamils, Tamil people native to Sri Lanka also called ilankai tamils
**Tamil Malaysians, Tamil people native to Malaysia
* Tamil language, nati ...
work ''
Purananuru
The ''Purananuru'' (, literally "four hundred oemsin the genre puram"), sometimes called ''Puram'' or ''Purappattu'', is a classical Tamil poetic work and traditionally the last of the Eight Anthologies (''Ettuthokai'') in the Sangam literatu ...
'', in connection with the death of the south Indian
Chera king
Yanaikatchai Mantaran Cheral Irumporai
Mantharan Cheral Irumporai ( Tamil: மாந்தரன் சேரல் இரும்பொறை) was a ruler of the Chera dynasty in early historic south India (c. 1st - 4th century CE).
Biography
He was a warring ruler, and const ...
.
The 374 AD and 607 approaches each came within 0.09
au of Earth.
The 451 AD apparition was said to herald the defeat of
Attila the Hun
Attila (, ; ), frequently called Attila the Hun, was the ruler of the Huns from 434 until his death in March 453. He was also the leader of a tribal empire consisting of Huns, Ostrogoths, Alans, and Bulgars, among others, in Central and Ea ...
at the
Battle of Chalons
The Battle of the Catalaunian Plains (or Fields), also called the Battle of the Campus Mauriacus, Battle of Châlons, Battle of Troyes or the Battle of Maurica, took place on June 20, 451 AD, between a coalition – led by the Roman general ...
. The 684 AD apparition was recorded in Europe in one of the sources used by the compiler of the 1493
Nuremberg Chronicle
The ''Nuremberg Chronicle'' is an illustrated encyclopedia consisting of world historical accounts, as well as accounts told through biblical paraphrase. Subjects include human history in relation to the Bible, illustrated mythological creatures, ...
s, which contains an image 8 centuries after the event. Chinese records also report it as the "broom star".
In 837, Halley's Comet may have passed as close as 0.03 au (3.2 million miles; 5.1 million kilometres) from
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
, by far its closest approach.
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;
Emperor
Louis the Pious
Louis the Pious (german: Ludwig der Fromme; french: Louis le Pieux; 16 April 778 – 20 June 840), also called the Fair, and the Debonaire, was King of the Franks and co-emperor with his father, Charlemagne, from 813. He was also King of Aqui ...
observed this appearance and devoted himself to prayer and penance, fearing that "by this token a change in the realm and the death of a prince are made known." In 912, Halley is recorded in the ''
Annals of Ulster
The ''Annals of Ulster'' ( ga, Annála Uladh) are annals of medieval Ireland. The entries span the years from 431 AD to 1540 AD. The entries up to 1489 AD were compiled in the late 15th century by the scribe Ruaidhrí Ó Luinín, ...
'', which state "A dark and rainy year. A comet appeared."
1066
![Comet Halley from London on 1066-05-06](https://upload.wikimedia.org/wikipedia/commons/c/ce/Comet_Halley_from_London_on_1066-05-06.png)
In 1066, the comet was seen in England and thought to be an
omen
An omen (also called ''portent'') is a phenomenon that is believed to foretell the future, often signifying the advent of change. It was commonly believed in ancient times, and still believed by some today, that omens bring divine messages fr ...
: later that year
Harold II of England died at the
Battle of Hastings
The Battle of Hastings nrf, Batâle dé Hastings was fought on 14 October 1066 between the Norman-French army of William the Conqueror, William, the Duke of Normandy, and an English army under the Anglo-Saxons, Anglo-Saxon King Harold Godw ...
and
William the Conqueror
William I; ang, WillelmI (Bates ''William the Conqueror'' p. 33– 9 September 1087), usually known as William the Conqueror and sometimes William the Bastard, was the first House of Normandy, Norman List of English monarchs#House of Norman ...
claimed the throne. The comet is represented on the
Bayeux Tapestry and described in the
tituli
:''See also Titulus (Roman Catholic) for Roman churches called tituli, or titulus (disambiguation) for more meanings.''
''Titulus'' (Latin "inscription" or "label", the plural ''tituli'' is also used in English) is a term used for the labels or ...
as a star. Surviving accounts from the period describe it as appearing to be four times the size of
Venus
Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...
, and shining with a light equal to a quarter of that of the
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
. Halley came within 0.10
au of Earth at that time.
This appearance of the comet is also noted in the ''
Anglo-Saxon Chronicle
The ''Anglo-Saxon Chronicle'' is a collection of annals in Old English, chronicling the history of the Anglo-Saxons. The original manuscript of the ''Chronicle'' was created late in the 9th century, probably in Wessex, during the reign of Alf ...
''.
Eilmer of Malmesbury
Eilmer of Malmesbury (also known as Oliver due to a scribe's miscopying, or Elmer, or Æthelmær) was an 11th-century English Benedictine monk best known for his early attempt at a gliding flight using wings.
Life
Eilmer was a monk of Malmesb ...
may have seen Halley in 989 and 1066, as recorded by
William of Malmesbury:
"Not long after, a comet, portending (they say) a change in governments, appeared, trailing its long flaming hair through the empty sky: concerning which there was a fine saying of a monk of our monastery called Æthelmær. Crouching in terror at the sight of the gleaming star, ‘You've come, have you?’, he said. ‘You've come, you source of tears to many mothers. 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.’"[William of Malmesbury; ''Gesta regum Anglorum / The history of the English Kings'', edited and translated by Mynors, R. A. B.; Thomson, R. M.; and Winterbottom, M.; 2 vols., Oxford Medieval Texts (1998–99), p. 121]
The Irish ''
Annals of the Four Masters
The ''Annals of the Kingdom of Ireland'' ( ga, Annála Ríoghachta Éireann) or the ''Annals of the Four Masters'' (''Annála na gCeithre Máistrí'') are chronicles of medieval Irish history. The entries span from the Deluge, dated as 2,24 ...
'' recorded the comet as "A star
hatappeared on the seventh of the
Calends
The calends or kalends ( la, kalendae) is the first day of every month in the Roman calendar. The English word "calendar" is derived from this word.
Use
The Romans called the first day of every month the ''calends'', signifying the start of a ne ...
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."
Chaco Native Americans in
New Mexico
)
, population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano)
, seat = Santa Fe
, LargestCity = Albuquerque
, LargestMetro = Tiguex
, OfficialLang = None
, Languages = English, Spanish ( New Mexican), Navajo, Ker ...
may have recorded the 1066 apparition in their petroglyphs.
The Italo-Byzantine chronicle of
Lupus the Protospatharios mentions that a "comet-star" appeared in the sky in the year 1067 (the chronicle is erroneous, as the event occurred in 1066, and by Robert he means William).
The Emperor Constantine Ducas
Constantine X Doukas or Ducas ( el, Κωνσταντῖνος Δούκας, ''Kōnstantinos X Doukas'', 1006 – 23 May 1067), was Byzantine emperor from 1059 to 1067. He was the founder and first ruling member of the Doukid dynasty. Duri ...
died in the month of May, and his son Michael received the Empire. And in this year there appeared a comet star, and the Norman count Robert icfought a battle with Harold, King of the English, and Robert was victorious and became king over the people of the English.
1145–1378
![Giotto - Scrovegni - -18- - Adoration of the Magi](https://upload.wikimedia.org/wikipedia/commons/f/f9/Giotto_-_Scrovegni_-_-18-_-_Adoration_of_the_Magi.jpg)
The 1145 apparition was recorded by the monk Eadwine. The 1986 apparition exhibited a fan tail similar to Eadwine's drawing.
Some claim that
Genghis Khan
''Chinggis Khaan'' ͡ʃʰiŋɡɪs xaːŋbr />Mongol script: ''Chinggis Qa(gh)an/ Chinggis Khagan''
, birth_name = Temüjin
, successor = Tolui (as regent)Ögedei Khan
, spouse =
, issue =
, house = Borjigin
, ...
was inspired to turn his conquests toward Europe by the 1222 apparition. 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
The Scrovegni Chapel ( it, Cappella degli Scrovegni ), also known as the Arena Chapel, is a small church, adjacent to the Augustinian monastery, the ''Monastero degli Eremitani'' in Padua, region of Veneto, Italy. The chapel and monastery ar ...
cycle, completed in 1305.
Its 1378 appearance is recorded in the ''Annales Mediolanenses'' as well as in East Asian sources.
1456
In 1456, the year of Halley's next apparition, the
Ottoman Empire
The Ottoman Empire, * ; is an archaic version. The definite article forms and were synonymous * and el, Оθωμανική Αυτοκρατορία, Othōmanikē Avtokratoria, label=none * info page on book at Martin Luther University) ...
invaded the
Kingdom of Hungary
The Kingdom of Hungary was a monarchy in Central Europe that existed for nearly a millennium, from the Middle Ages into the 20th century. The Principality of Hungary emerged as a Christian kingdom upon the coronation of the first king Stephen ...
, 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
Bartolomeo Sacchi (; 1421 – 21 September 1481), known as Platina (in Italian ''il Platina'' ) after his birthplace (Piadena), and commonly referred to in English as Bartolomeo Platina, was an Italian Renaissance humanist writer and gastro ...
wrote in his ''
Lives of the Popes
Lives may refer to:
* The plural form of a ''life''
* Lives, Iran, a village in Khuzestan Province, Iran
* The number of lives in a video game
* ''Parallel Lives'', aka ''Lives of the Noble Greeks and Romans'', a series of biographies of famous me ...
'' that,
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.
![PSM V76 D015 Halley comet in 1456](https://upload.wikimedia.org/wikipedia/commons/9/9f/PSM_V76_D015_Halley_comet_in_1456.png)
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.
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).
After witnessing a bright light in the sky which most historians have identified as Halley's Comet,
Zara Yaqob
Zara Yaqob ( Ge'ez: ዘርዐ ያዕቆብ; 1399 – 26 August 1468) was Emperor of Ethiopia, and a member of the Solomonic dynasty who ruled under the regnal name Kwestantinos I (Ge'ez: ቈስታንቲኖስ, "Constantine"). He is known for t ...
, Emperor of
Ethiopia
Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...
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
In the
Sikh
Sikhs ( or ; pa, ਸਿੱਖ, ' ) are people who adhere to Sikhism, Sikhism (Sikhi), a Monotheism, monotheistic religion that originated in the late 15th century in the Punjab region of the Indian subcontinent, based on the revelation of Gu ...
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.
1531–1759
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 it would return. One key breakthrough occurred when Halley talked with Newton about his ideas of the laws of motion. Newton also helped Halley get Flamsteed's data on the 1682 apparition.
By studying data on the 1531, 1607, and 1682 comets, he came to the conclusion these were the same comet, and presented his findings in 1696.
One difficulty was accounting for variations in the comet's orbital period, which was over a year longer between 1531 and 1607 than it was between 1607 and 1682.
[Sagan, Carl; Druyan, Ann; ''Comet'', p. 57] Newton had theorized that such delays were caused by the gravity of other comets, but Halley found that Jupiter and Saturn would cause the appropriate delays.
In the decades that followed, more refined mathematics would be worked on, notable by Paris Observatory; the work on Halley also provided a boost to Newton and Kepler's rules for celestial motions.
(See also
#Computation of orbit)
1835
At
Markree Observatory in Ireland, a E. J. Cooper used a Cauchoix of Paris lens telescope with an aperture of to sketch Halley's comet in 1835.
The comet was also sketched by F.W. Bessel. Streams of vapour observed during the comet's 1835 apparition prompted astronomer
Friedrich Wilhelm Bessel to propose that the
jet force Jet force is the exhaust from some machine, esp. aircraft, propelling the object itself in the opposite direction as per Newton's laws of motion, Newton's Third Law. An understanding of jet force is intrinsic to the launching of drones, satellites, ...
s of evaporating material could be great enough to significantly alter a comet's orbit.
An interview in 1910, of someone who was a teenager at the time of the 1835 apparition had this to say:
They go on to describe the comet's tail as being more broad and not as long as the comet of 1843 they had also witnessed.
Famous astronomers across the world made observations starting August 1835, including Struve at Dorpat observatory, and Sir John Herschel, who made of observations from the Cape of Good Hope.
In the United States telescopic observations were made from
Yale College
Yale College is the undergraduate college of Yale University. Founded in 1701, it is the original school of the university. Although other Yale schools were founded as early as 1810, all of Yale was officially known as Yale College until 1887, ...
.
The new observations helped confirm early appearances of this comet including its 1456 and 1378 apparitions.
At Yale College in Connecticut, the comet was first reported on 31 August 1835 by astronomers D. Olmstead and E. Loomis.
In Canada reports were made from Newfoundland and also Quebec.
Reports came in from all over by later 1835, and often reported in newspapers of this time in Canada.
Several accounts of the 1835 apparition were made by observers who survived until the 1910 return, where increased interest in the comet led to their being interviewed.
Astrophotography was not known to have been attempted until 1839, as photography was still being invented in the 1830s, too late to photograph the apparition of 1P/Halley in 1835.
The time to Halley's return in 1910 would be only 74.42 years, one of the shortest known periods of its return, which is calculated to be as long as 79 years owing to the effects of the planets.
At
Paris Observatory
The Paris Observatory (french: Observatoire de Paris ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its histor ...
Halley's Comet 1835 apparition was observed with a Lerebours telescope of 24.4 cm (9.6 in) aperture by the astronomer
François Arago
Dominique François Jean Arago ( ca, Domènec Francesc Joan Aragó), known simply as François Arago (; Catalan: ''Francesc Aragó'', ; 26 February 17862 October 1853), was a French mathematician, physicist, astronomer, freemason, supporter of t ...
.
Arago recorded polimetric observations of Halley, and suggested that the tail might be sunlight reflecting off a sparsely distributed material; he had earlier made similar observations of
Comet Tralles
The Great Comet of 1819, officially designated as C/1819 N1, also known as Comet Tralles, was an Great comet, exceptionally bright and easily visible comet, approaching an apparent magnitude of 1–2, discovered July 1, 1819 by the German astrono ...
of 1819.
1910
![PSM V76 D020 Path of halley comet](https://upload.wikimedia.org/wikipedia/commons/4/4d/PSM_V76_D020_Path_of_halley_comet.png)
The 1910 approach, which came into naked-eye view around 10 April
and came to perihelion on 20 April,
was notable for several reasons: it was the first approach of which photographs exist, and the first for which
spectroscopic data were obtained.
Furthermore, the comet made a relatively close approach of 0.15 au,
making it a spectacular sight. Indeed, on 19 May, Earth actually passed through the tail of the comet.
One of the substances discovered in the tail by spectroscopic analysis was the toxic gas
cyanogen
Cyanogen is the chemical compound with the formula ( C N)2. It is a colorless and highly toxic gas with a pungent odor. The molecule is a pseudohalogen. Cyanogen molecules consist of two CN groups – analogous to diatomic halogen molecule ...
, which led astronomer
Camille Flammarion
Nicolas Camille Flammarion FRAS (; 26 February 1842 – 3 June 1925) was a French astronomer and author. He was a prolific author of more than fifty titles, including popular science works about astronomy, several notable early science fiction ...
to claim that, when Earth passed through the tail, the gas "would impregnate the atmosphere and possibly snuff out all life on the planet."
His pronouncement led to panicked buying of gas masks and quack "anti-comet pills" and "anti-comet umbrellas" by the public. In reality, as other astronomers were quick to point out, the gas is so diffused that the world suffered no ill effects from the passage through the tail.
The comet added to the unrest in China on the eve of the
Xinhai Revolution
The 1911 Revolution, also known as the Xinhai Revolution or Hsinhai Revolution, ended China's last imperial dynasty, the Manchu-led Qing dynasty, and led to the establishment of the Republic of China. The revolution was the culmination of a d ...
that would end the
last dynasty in 1911. As James Hutson, a missionary in
Sichuan
Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of the ...
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."
The 1910 visitation is also recorded as being the travelling companion of
Hedley Churchward
Al-Hajj Hedley Cole Churchward (Mahmoud Mobarek) (1862 Walmer, Kent–28 August 1929 Johannesburg), was an English set designer and painter, notable for converting to Islam and in 1910 being the first known British Muslim to make the Hajj.
Ea ...
, the first known English Muslim to make the Haj pilgrimage to
Mecca
Mecca (; officially Makkah al-Mukarramah, commonly shortened to Makkah ()) is a city and administrative center of the Mecca Province of Saudi Arabia, and the Holiest sites in Islam, holiest city in Islam. It is inland from Jeddah on the Red ...
. However, his explanation of its scientific predictability did not meet with favour in the Holy City.
The comet was used in an advertising campaign of
Le Bon Marché, a well-known department store in Paris.
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.
American satirist and writer
Mark Twain
Samuel Langhorne Clemens (November 30, 1835 – April 21, 1910), known by his pen name Mark Twain, was an American writer, humorist, entrepreneur, publisher, and lecturer. He was praised as the "greatest humorist the United States has p ...
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.'
Twain died on 21 April 1910, the day following the comet's subsequent perihelion. 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.
1986
![Animation of 1P/Halley orbit - 1986 apparition](https://upload.wikimedia.org/wikipedia/commons/4/4a/Animation_of_1P%EF%BC%8FHalley_orbit_-_1986_apparition.gif)
The 1986 apparition of Halley's Comet was the least favourable on record. In February 1986, the comet and the Earth were on opposite sides of the Sun, creating the worst possible viewing circumstances for Earth observers during the previous 2,000 years. Halley's closest approach was 0.42 au. Additionally, increased
light pollution
Light pollution is the presence of unwanted, inappropriate, or excessive use of artificial Visible spectrum, lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting, during the day ...
from urbanization caused many people to fail in attempts to see the comet. With the help of binoculars, observation from areas outside cities was more successful. Further, the comet appeared brightest when it was almost invisible from the northern hemisphere in March and April 1986, with best opportunities occurring when the comet could be sighted close to the horizon at dawn and dusk, if not obscured by clouds.
The approach of the comet was first detected by astronomers
David C. Jewitt
David Clifford Jewitt (born 1958) is a British-American astronomer who studies the Solar System, especially its minor bodies. He is based at the University of California, Los Angeles, where he is a Member of the Institute for Geophysics and Pl ...
and G. Edward Danielson on 16 October 1982 using the 5.1 m
Hale telescope at
Mount Palomar
Palomar Mountain ( ; es, Monte Palomar ) is a mountain ridge in the Peninsular Ranges in northern San Diego County. It is famous as the location of the Palomar Observatory and Hale Telescope, and known for the Palomar Mountain State Park.
Hist ...
and a
CCD camera
A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
.
The first visual observance of the comet on its 1986 return was by an amateur astronomer, Stephen James O'Meara, on 24 January 1985. O'Meara used a home-built telescope on top of
Mauna Kea
Mauna Kea ( or ; ; abbreviation for ''Mauna a Wākea''); is a dormant volcano on the island of Hawaii. Its peak is above sea level, making it the highest point in the state of Hawaii and second-highest peak of an island on Earth. The peak is ...
to detect the
magnitude 19.6 comet.
[ (Horizons shows the nucleus @ APmag +20.5; the coma up to APmag +14.3)] The first to observe Halley's Comet with the naked eye during its 1986 apparition were Stephen Edberg (then serving as the coordinator for amateur observations at the
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
Jet Propulsion Laboratory
The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States.
Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...
) and Charles Morris on 8 November 1985.
Although the comet's retrograde orbit and high inclination made it difficult to send a space probe to it,
the 1986 apparition gave scientists the opportunity to study the comet closely and several probes were launched to do so. The Soviet
Vega 1 probe began returning images of Halley on 4 March 1986, captured the first-ever image of its
nucleus
Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to:
*Atomic nucleus, the very dense central region of an atom
*Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA
Nucle ...
,
and made its flyby on 6 March. It was followed by the
Vega 2
Vega 2 (along with Vega 1) was a Soviet space probe part of the Vega program to explore Halley's comet and Venus. The spacecraft was a development of the earlier ''Venera'' craft. The name VeGa (ВеГа) combines the first two letters Russian wo ...
probe, making its flyby on 9 March. On 14 March, the
''Giotto'' space probe, launched by the
European Space Agency
, owners =
, headquarters = Paris, Île-de-France, France
, coordinates =
, spaceport = Guiana Space Centre
, seal = File:ESA emblem seal.png
, seal_size = 130px
, image = Views in the Main Control Room (1205 ...
, made the closest pass of the comet's nucleus.
There also were two Japanese probes,
''Suisei'' and ''
Sakigake''. Unofficially, the numerous probes became known as the
Halley Armada.
Based on data retrieved by the largest
ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
space telescope of the time,
''Astron'', during its Halley's Comet observations in December 1985, a group of Soviet scientists developed a model of the comet's
coma
A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...
. The comet also was observed from space by the
International Cometary Explorer (ICE). Originally named International Sun-Earth Explorer 3, the probe was renamed and freed from its
Lagrangian point
In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of th ...
location in Earth's orbit in order to intercept comets
21P/Giacobini-Zinner and Halley. ICE flew about 40.2 million km (25 million mi) from Halley's Comet on 28 March 1986.
Two
Space Shuttle
The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
missions—the
STS-51-L
STS-51-L was the 25th mission of the NASA Space Shuttle program and the final flight of Space Shuttle ''Challenger''.
Planned as the first Teacher in Space Project flight in addition to observing Halley's Comet for six days and performing a ...
and the
STS-61-E
STS-61-E was a NASA Space Shuttle mission planned to launch on 6 March 1986 using ''Columbia''. It was canceled after the ''Challenger'' disaster.
Crew
Mission objectives
''Columbia'' was to carry the ASTRO-1 observatory, which would b ...
—had been scheduled to observe Halley's Comet from
low Earth orbit
A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...
. The STS-51-L mission carried the Shuttle-Pointed Tool for Astronomy (SPARTAN-203) satellite, also called the Halley's Comet Experiment Deployable (HCED). The ill-fated mission was ended by the
''Challenger'' disaster. Scheduled for March 1986, STS-61-E was a ''Columbia'' mission carrying the ASTRO-1 platform to study the comet. Owing to the suspension of the American human spaceflight program after the ''Challenger'' explosion, the mission was canceled and ASTRO-1 would not fly until late 1990 on
STS-35
STS-35 was the tenth flight of Space Shuttle ''Columbia'', the 38th shuttle flight, and a mission devoted to astronomical observations with ASTRO-1, a Spacelab observatory consisting of four telescopes. The mission launched from Kennedy Spac ...
.
After 1986
![ESO-Comet Halley at 28 AU-phot-27a-03-fullres](https://upload.wikimedia.org/wikipedia/commons/a/ae/ESO-Comet_Halley_at_28_AU-phot-27a-03-fullres.jpg)
On 12 February 1991, at a distance of from the Sun, Halley displayed an outburst that lasted for several months, releasing a cloud of dust across.
The outburst likely started in December 1990, and then the comet brightened from magnitude 24.3 to magnitude 18.9.
Halley was most recently observed in 2003 by three of the
Very Large Telescope
The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m across, ...
s 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.
Astronomers are now able to observe the comet at any point in its orbit.
On 9 December 2023, Halley's Comet will reach the farthest and slowest point in its orbit from the Sun when it will be traveling at with respect to the Sun.
2061
![Animation of 1P/Halley orbit - 2061 apparition](https://upload.wikimedia.org/wikipedia/commons/0/04/Animation_of_1P%EF%BC%8FHalley_orbit_-_2061_apparition.gif)
The next perihelion of Halley's Comet is 28 July 2061,
when it will be better positioned for observation than during the 1985–1986 apparition, as it will be on the same side of the Sun as Earth.
The closest approach to Earth will be one day after perihelion.
[ It is expected to have an ]apparent magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...
of −0.3, compared with only +2.1 for the 1986 apparition. On 9 September 2060, Halley will pass within of Jupiter, and then on 20 August 2061 will pass within of Venus.
2134
Halley will come to perihelion on 27 March 2134. Then on 7 May 2134, Halley will pass within of Earth. Its apparent magnitude is expected to be −2.0.
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. 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 The half-month is a calendar subdivision used in astronomy. Each calendar month is separated into two parts:
*days 1 to 15
*day 16 until the end of the month.
Newly identified small Solar System bodies, such as comets and asteroids, are given syste ...
U (the second half of October) 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
Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...
1982i). The perihelion dates of each apparition are shown. 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
The Julian calendar, proposed by Roman consul Julius Caesar in 46 BC, was a reform of the Roman calendar. It took effect on , by edict. It was designed with the aid of Greek mathematicians and astronomers such as Sosigenes of Alexandr ...
, while perihelion dates 1607 and after are in the Gregorian calendar
The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years dif ...
.
Halley's Comet is visible from Earth every 74–79 years.
See also
* List of Halley-type comets
* Halley's Comet in fiction
* Kepler orbit
References
Bibliography
*
*
*
*
External links
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)
1P/Halley at CometBase database
Orbital simulation
from JPL (Java)
Ephemeris
*
Donald Keith Yeomans, "Great Comets in History"
( 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
{{DEFAULTSORT:Halley, 001P
Astronomical objects known since antiquity
Comets visited by spacecraft
Halley-type comets
Meteor shower progenitors
001P
0001
Periodic comets
Star of Bethlehem