1P/Halley

Discovery
Discovered by:	prehistoric; Named after Edmond Halley
Discovery date:	1758 (first predicted perihelion)
Alternate designations:	Halley's Comet, 1P (see Designation below)
Orbital characteristics A
Epoch:	2449400. Edmond Halley FRS (ˈɛdmənd ˈhɔːlɪ ( November 8, 1656 &ndash January 14, 1742) was an English Astronomer A provisional designation in astronomy is the naming convention applied to Astronomical objects immediately following their discovery Halley's Comet, officially designated 1P/Halley and also referred to as Comet Halley after Edmond Halley, is a Comet that can be seen every In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. 5 (February 17, 1994)
Aphelion distance:	35. Events 1500 - Battle of Hemmingstedt. 1600 - Philosopher Giordano Bruno is burned alive at Campo de' Fiori Year 1994 ( MCMXCIV) was a Common year starting on Saturday (link will display full 1994 Gregorian calendar) In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from 1 AU (December 9, 2023)[1]
Perihelion distance:	0. Events 536 - Byzantine General Belisarius enters Rome while the Ostrogothic garrison peacefully leaves the city 2023 ( MMXXIII) will be a Common year starting on Sunday of the Gregorian calendar. In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from 586 AU
Semi-major axis:	17. In Geometry, the semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae 8 AU
Eccentricity:	0. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the In Astrodynamics, under standard assumptions, any Orbit must be of Conic section shape 967
Orbital period:	75. The orbital period is the time taken for a given object to make one complete Orbit about another object 3 a
Inclination:	162. In Astronomy, a Julian year (symbol a) is a unit of measurement of Time defined Inclination in general is the Angle between a Reference plane and another plane or axis of direction 3°
Last perihelion:	February 9, 1986
Next perihelion:	July 28, 2061[1]

Halley's Comet, officially designated 1P/Halley and also referred to as Comet Halley after Edmond Halley, is a comet that can be seen every 75–76 years. Events 474 - Zeno crowned as co-emperor of the Byzantine Empire. Year 1986 ( MCMLXXXVI) was a Common year starting on Wednesday (link displays 1986 Gregorian calendar) Events 1540 - Thomas Cromwell is executed at the order of Henry VIII of England on charges of Treason. Notable predictions and known events 2061 Expected expiration of the Singapore-Malaysia Water Agreement. Edmond Halley FRS (ˈɛdmənd ˈhɔːlɪ ( November 8, 1656 &ndash January 14, 1742) was an English Astronomer A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — It is the most famous of all periodic comets. Periodic comets are defined for these purposes as those Comets having orbital periods of less than 200 years (also known as "short-period comets" or which Although in every century many long-period comets appear brighter and more spectacular, Halley is the only short-period comet that is clearly visible to the naked eye, and thus, the only naked-eye comet certain to return within a human lifetime. ^[2] Halley's Comet last appeared in the inner Solar System in 1986, and will next appear in mid 2061. The Solar System consists of the Sun and those celestial objects bound to it by Gravity.

Pronunciation

Halley is generally pronounced /ˈhælɪ/, rhyming with valley, or (especially in the US) /ˈheɪlɪ/ "Hailey", but Edmond Halley himself pronounced his name /ˈhɔːlɪ/ "Hawley", with the "hall-" rhyming with "call" or "small". ^[3] The "Hailey" pronunciation led to rock and roll singer Bill Haley naming his band The Comets. Rock and roll (also known as rock 'n' roll) is a form of Music that evolved in the United States in the late 1940s and early 1950s with roots in mostly African This article is specifically about the singer For detailed information about his rock and roll group see Bill Haley & His Comets. This article is specifically about the rock and roll band See Bill Haley for biographical information regarding Haley himself

Edmond Halley's study

Halley's Comet was the first comet to be recognized as periodic. Perceiving that the observed characteristics of the comet of 1682 were nearly the same as those of two comets which had appeared in 1531 (observed by Petrus Apianus) and 1607 (observed by Johannes Kepler in Prague), Halley concluded that all three comets were in fact the same object returning every 76 years (a period that has since been amended to every 75–76 years). Petrus Apianus ( April 16, 1495 &ndash April 21, 1552; also known as Peter Apian) was a German Johannes Kepler (ˈkɛplɚ ( December 27 1571 &ndash November 15 1630) was a German Mathematician, Astronomer Prague (ˈprɑːg Praha (ˈpraɦa see also other names) is the Capital and Largest city of the Czech Republic. After a rough estimate of the perturbations the comet would sustain from the attraction of the planets, he predicted its return for 1758. Halley's prediction of the comet's return proved to be correct, although it was not seen until 25 December 1758 by Johann Georg Palitzsch, a German farmer and amateur astronomer, and did not pass through its perihelion until March 13, 1759; the attraction of Jupiter and Saturn having caused a retardation of 618 days, as was computed by a team of three French mathematicians, Alexis Clairault, Joseph Lalande, and Nicole-Reine Lepaute, previous to its return. Events 274 - Roman Emperor Aurelian Year 1758 ( MDCCLVIII) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a Common Johann Georg Palitzsch ( June 11 1723 &ndash February 21 1788) was a German Astronomer who became famous for discovering In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from This article is about the country For a topic outline on this subject see List of basic France topics. Alexis Claude de Clairault (or Clairaut) ( May 3, 1713 – May 17, 1765) was a French Mathematician and Joseph Jérôme Lefrançais de Lalande ( July 11, 1732 &ndash April 4, 1807) was a French Astronomer and writer Nicole-Reine Étable de la Brière Lepaute (1723-1788 was a French Astronomer. Halley did not live to see the comet's return, having died in 1742.

Notable appearances

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

Early appearances

A Babylonian tablet recording the appearance of Halley's comet in 164 BC. Babylonia was an Amorite state in lower Mesopotamia (modern southern Iraq) with Babylon as its capital

The comet's appearance in 1066 was recorded on the Bayeux Tapestry. The Bayeux Tapestry (Tapisserie de Bayeux is a 50 cm by 70 m (20 in by 230 ft long embroidered cloth which explains the events leading up to the 1066 Norman invasion of The caption, ISTI MIRANT STELLA, was translated in a 1966 National Geographic article as "These men wonder at the star. Overview The NGS's historical mission is "to increase and diffuse geographic knowledge while promoting the conservation of the world's cultural historical and natural "

• 240 BC and earlier: Historical records show that Chinese astronomers observed the comet's appearance in 240 BC and possibly as early as 467 BC. Habitual observations and calculations of appearances after 240 BC are recorded by Chinese, Babylonian, Persian, and other Mesopotamian astronomers.
• 87 BC: According to V. G. Gurzadyan and R. Vardanyan, the "Symbol on Tigranes the Great's crown that features a star with a curved tail may represent the passage of Halley's comet in 87 BC. This article is about a king of Armenia in the 1st century BCE. Tigranes could have seen Halley's comet when it passed closest to the Sun on Aug. 6 in 87 BC according to the researchers, who said the comet would have been a 'most recordable event' — heralding the New Era of the brilliant King of Kings. ^[4]
• 12 BC: Some theologians have suggested that the comet's appearance in 12 BC might explain the Biblical story of the Star of Bethlehem. Theology is the study of a god or the gods from a religious perspective See also Star of Bethlehem (plant. The Star of Bethlehem, also called the Christmas Star, is a star in Christian tradition ^[5]
• AD 66 : In the Talmud, it is mentioned that "There is a star which appears once in seventy years that makes the captains of the ships err". The Talmud ( Hebrew: he תַּלְמוּד is a record of Rabbinic discussions pertaining to Jewish law, ethics, customs and history ^[6] Since this quote is attributed to the Rabbi Yehoshua ben Hananiah, if it is indeed a reference to Halley's Comet, it probably refers to the AD 66 perihelion, which was the only one to occur during his lifetime. ^[7]
• 837: In this year, it is calculated that Comet Halley may have passed as close as 0. 03 AU (3. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the 2 million miles; 5. 1 million kilometres) from Earth, by far its closest approach. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Its tail may have stretched 90 degrees across the sky. This article describes the unit of angle For other meanings see Degree. ^[8]
• 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. Harold Godwinson, (c 1022 &ndash 14 October 1066 also known as Harold II, is widely regarded as the last Anglo-Saxon King of England before the The Battle of Hastings was the decisive Norman victory in the Norman Conquest of England. Thus it was a bad omen for Harold, but a good omen for William the Conqueror. William I of England ( 1027 His reign which brought Norman culture to England had an enormous impact on the subsequent course of England in the Middle Ages Shown on the Bayeux Tapestry, and the accounts which have been preserved represent it as having then appeared to be four times the size of Venus, and to have shone with a light equal to a quarter of that of the Moon. The Bayeux Tapestry (Tapisserie de Bayeux is a 50 cm by 70 m (20 in by 230 ft long embroidered cloth which explains the events leading up to the 1066 Norman invasion of The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University 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. Having first seen it as a young boy in 989, Eilmer of Malmesbury declared prophetically in 1066: "You've come, have you?…You've come, you source of tears to many mothers, you evil. Eilmer of Malmesbury (also known as Oliver due to a scribe's miscopying or Elmer) was an 11th-century English Benedictine monk best known 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!" ^[9]. Chaco Native Americans in New Mexico recorded this 1066 comet in their petroglyphs. ^[10]
• 1301: The artist Giotto di Bondone could have observed the comet and his depiction of the Star of Bethlehem in the Nativity in the Arena Chapel cycle completed in 1305 is a candidate for an early depiction. The Nativity of Jesus has been a major subject of Christian art since the 4th century The Scrovegni Chapel, or Cappella degli Scrovegni, also known as the Arena Chapel is a church in Padua, Veneto
• 1456: The comet passed very close to the Earth; its tail extended over 60° of the heavens and took the form of a sabre. According to one story, first appearing in a posthumous biography in 1475 and later embellished and popularized by Pierre-Simon Laplace, Pope Callixtus III excommunicated the 1456 apparition of the comet, believing it to be an ill omen for the Christian defenders of Belgrade, who were at that time being besieged by the armies of the Ottoman Empire. Pope Calixtus III ( December 31, 1378 &ndash August 6, 1458) né Alfonso de Borja, was Pope from April Excommunication is a religious Censure used to deprive or suspend membership in a religious community Belgrade (Београд Beograd is the Capital and largest city of Serbia. The Ottoman Empire (1299–1923 ( Old Ottoman Turkish: دولتْ علیّه عثمانیّه Devlet-i Âliye-yi Osmâniyye, Late Ottoman and Modern Turkish However, no known primary source supports the authenticity of this account.

Recent history

The most recent appearances have been in 1835, 1910, and 1986. Halley will next return in 2061.

1835

American satirist and writer Mark Twain was born on November 30, 1835, exactly two weeks after the comet's perihelion. Samuel Langhorne Clemens (November 30 1835 – April 21 1910 better known by the Pen name Mark Twain, was an American Humorist, satirist Events 1700 - Battle of Narva — A Swedish army of 8500 men under Charles XII defeats Year 1835 ( MDCCCXXXV) was a Common year starting on Thursday (link will display the full calendar of the Gregorian Calendar (or a Common In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from In his biography, he said, "I came in with Halley's comet in 1835. It's coming again next year (1910), and I expect to go out with it. 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 April 21, 1910, the day following the comet's subsequent perihelion. Events 753 BC - Romulus and Remus found Rome ( traditional date) Year 1910 ( MCMX) was a Common year starting on Saturday (link will display calendar of the Gregorian calendar (or a Common year starting ^[11][12] The 1985 fantasy film The Adventures of Mark Twain is inspired by this. The Adventures of Mark Twain, released in the UK as Comet Quest, is a 1985 Stop motion animated film directed by

1910

The April 1910 approach, which came into view around April 20, was notable for several reasons: it was the first approach of which photographs exist, and the comet made a relatively close approach, making it a spectacular sight. Events 1303 - The University of Rome La Sapienza is instituted by Pope Boniface VIII. Indeed, on May 18, the media, despite the pleas of astronomers, wove sensational tales of mass cyanide poisoning engulfing the planet. Events 1152 - Henry II of England marries Eleanor of Aquitaine. In reality, the gas is so diffuse that the world suffered no ill effects from the passage through the tail.

Many people who claim to remember seeing the 1910 apparition are probably in fact remembering a different comet, the Great Daylight Comet of 1910, which surpassed Halley in brilliance and was actually visible in broad daylight for a short time about four months before Halley made its appearance. The Great January comet of 1910 or Great Daylight comet was a Great comet that in January 1910 upstaged the much-anticipated appearance of Halley's Comet

1986

Comet Halley in 1986

The 1986 approach was the least favourable for Earth observers of all recorded passages of the comet throughout history: the comet did not achieve the spectacular brightness of some previous approaches, and with increased light pollution from urbanization, many people never saw the comet at all. Light pollution, also known as photopollution or luminous pollution, is excess or obtrusive Light created mainly by Humans Among other effects Further, the comet appeared brightest when it was almost invisible from the northern hemisphere in March and April, prompting many amateur astronomers to travel to the southern hemisphere for a glimpse of the interloper. However, the development of space travel allowed scientists the opportunity to study the comet at close quarters, and several probes were launched to do so. The Soviet Vega 1 started returning images of Halley on 1986 March 4, and the first ever of its nucleus, and made its flyby on March 6, followed by Vega 2 making its flyby on March 9. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 Vega 1 (along with its twin Vega 2) is a Soviet Space probe part of the Vega program. Year 1986 ( MCMLXXXVI) was a Common year starting on Wednesday (link displays 1986 Gregorian calendar) Events 51 - Nero, later to become Roman Emperor, is given the title Princeps iuventutis (head of the youth The nucleus is the solid central part of a Comet, popularly termed a dirty snowball. Vega 2 (along with Vega 1) is a Soviet Space probe part of the Vega program. On March 14, the Giotto space probe, launched by the European Space Agency, made a closest pass of the comet's nucleus. Giotto was a European Robotic spacecraft mission from the European Space Agency, intended to fly by and study Halley's Comet. The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member There were also two Japanese probes, Suisei and Sakigake. For a topic outline on this subject see List of basic Japan topics. Suisei (すいせい Japanese for Comet) originally known as Planet-A, was an unmanned Space probe developed by the Institute of Sakigake may also refer to Sakigake!! Kuromati Koko, an anime The probes were unofficially known as the Halley Armada. The Halley Armada is a group of space probes sent to examine Comet Halley during its 1986 sojourn through the inner solar system

The first person to visually observe comet Halley on its 1986 return was amateur astronomer Stephen James O'Meara on January 24, 1985. Events 41 - Gaius Caesar (Caligula, known for his eccentricity and cruel Despotism, is Assassinated by his disgruntled Year 1985 ( MCMLXXXV) was a Common year starting on Tuesday (link displays 1985 Gregorian calendar) O'Meara used a home-built 24" telescope on top of Mauna Kea to detect the magnitude 19. Mauna Kea is a Dormant volcano in the Hawaiian Islands, one of five volcanoes which together form the Island of Hawaii. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 6 comet. ^[13] As for the naked eye observing, it was Stephen Edberg (then serving as the Coordinator for Amateur Observations at NASA's Jet Propulsion Laboratory) and Charles Morris who were the first to observe Comet Halley with the naked eye in its 1986 apparition. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program

During the Halley's Comet viewing, Yuma, Arizona, was the best place to see the comet without machine. Yuma is a city in and the County seat of Yuma County, Arizona, United States. During the week of April 4, the city of Yuma gave the title "Halley's Comet Baby" to the first baby born during that week. Events 1581 - Francis Drake completes a circumnavigation of the world and is knighted by Elizabeth I.

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. Astron was a Soviet astrophysical spacecraft launched on March 23 1983 at 124506 UTC by Proton launcher. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 In Astronomy, a coma (from the Latin word for "hair" is the nebulous envelope around the nucleus of a Comet. ^[14] The comet was also observed from space by the International Cometary Explorer. The International Cometary Explorer (ICE Spacecraft was originally known as International Sun/Earth Explorer 3 (ISEE-3 satellite launched August 12, 1978 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. Comet Giacobini-Zinner is a Periodic comet in our solar system and was discovered by Michel Giacobini ( Nice, France) in Aquarius

Two Space Shuttle missions — the ill-fated STS-51-L (the Challenger disaster) and STS-61-E — were scheduled to observe Comet Halley from low Earth orbit. NASA 's Space Shuttle, officially called the Space Transportation System ( STS) is the Spacecraft currently used by the United States STS-51-L was the twenty-fifth flight of the American Space Shuttle program, which marked the first time a civilian had flown aboard the Space Shuttle The Space Shuttle Challenger disaster took place on January 28 1986 when ''Challenger'', a Space Shuttle operated by NASA, broke apart A Low Earth Orbit (LEO is generally defined as an Orbit within the locus extending from the Earth’s surface up to an altitude of 2000 km 61-E would have been flown by Challenger in March 1986, carrying the ASTRO-1 platform to study the comet. Space Shuttle Challenger ( NASA Orbiter Vehicle Designation: OV-099 was NASA's second Space Shuttle orbiter to be put into service 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 thirty-eighth shuttle flight and a mission devoted to deploying ASTRO-1 an observatory consisting ^[15]

Origin

Comets are believed to have two separate points of origin in the Solar System: the Kuiper belt, a flat disc of icy debris between 38 AU (Pluto's orbit) and 50 AU from the Sun, and the Oort cloud, a sphere of cometary bodies which has its inner edge at 50,000 AU. The Kuiper belt (ˈkaɪpɚ to rhyme with "viper" sometimes called the Edgeworth-Kuiper belt, is a region of the Solar System beyond the planets extending The Oort cloud ( ort alternatively the Öpik-Oort Cloud) is a hypothetical spherical cloud of Comets believed to lie roughly 50 000 AU, Short period comets (those with orbits lasting 200 years or less) are generally accepted to have emerged from the Kuiper belt, while long period comets, such as Hale-Bopp, whose orbits last for thousands of years, are believed to originate in the Oort cloud. A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — Comet Hale-Bopp ( formally designated C/1995 O1) was probably the most widely observed Comet of the twentieth century and one of the brightest Halley is unusual in that while it is a short period comet, its ultimate origin lies in the Oort cloud, not the Kuiper belt. Its orbit is such that it is believed to have been originally a long period comet but to have been captured by the gravity of the giant planets and sent into the inner Solar System. Halley is grouped with other comets that share this orbit into the Halley family comets. ^[16]

Orbit

The orbits of three periodic comets, Halley, Borrelly and Ikeya-Zhang, set against the orbits of the outer planets and Pluto. Periodic comets are defined for these purposes as those Comets having orbital periods of less than 200 years (also known as "short-period comets" or which Comet Borrelly (formally designated 19P/Borrelly) is a periodic Comet, which was visited by the space craft Deep Space 1. The Solar System consists of the Sun and those celestial objects bound to it by Gravity. Halley's is to the left

Halley's orbit is highly elliptical, and focused on the Sun. In Mathematics, an ellipse (from the Greek ἔλλειψις literally absence) is a Conic section, the locus of points in a Its perihelion, its closest distance to the Sun, is just 0. In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from 6 AU (between the orbits of Mercury and Venus), while its aphelion, or farthest distance from the Sun, is 35 AU, or roughly the distance of Pluto. The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from Unusually 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. Direct motion is the motion of a Planetary body in a direction similar to that of other bodies within its system and is sometimes called prograde motion. The Sun (Sol is the Star at the center of the Solar System. Its orbit is highly inclined (18°) to the ecliptic, with much of it lying below the orbits of the planets (assuming Earth's north pole is "up"). The ecliptic is the apparent path that the Sun traces out in the sky during the year ^[17][18]

Due to Halley's highly eccentric orbit, it has one of the highest velocities relative to the Earth in the solar system. The 1910 passage was at a relative velocity of 70. In Kinematics, relative velocity is the vector difference between the velocities of two objects as evaluated in terms of a single Coordinate 56 km/s (157,800 MPH). ^[19]

Structure and composition

The Giotto mission gave planetary scientists their first view of Halley's surface and structure. Although its coma may extend about 100 million kilometres into space,^[20] Halley's nucleus is relatively small (barely 15 kilometres long, 8 kilometres wide and 8 kilometres thick) and roughly peanut-shaped. In Astronomy, a coma (from the Latin word for "hair" is the nebulous envelope around the nucleus of a Comet. The nucleus is the solid central part of a Comet, popularly termed a dirty snowball. The peanut, or Groundnut ( Arachis hypogaea) is a species in the Legume family Fabaceae native to South America, Mexico Its mass is extremely low; roughly 2. 2×10¹⁴ kg. ^[21] Its average density is about 0. 6 g/cm³, indicating that it is very loosely constructed. ^[22] Its albedo is about 4 percent, meaning that only 4 percent of the sunlight hitting it is reflected; about what one would expect for coal. The albedo of an object is the extent to which it diffusely reflects light from the sun Thus, despite appearing brilliant white to observers on Earth, Halley's comet is in fact pitch black. Its nucleus has an albedo only of 0. The albedo of an object is the extent to which it diffusely reflects light from the sun 03, darker than coal. As it approaches the inner Solar System, the Sun warms it, causing its surface to sublimate (change directly from a solid to a gas), and jets of volatile material to burst from its black surface. Sublimation of an element or compound is a transition from the Solid to Gas phase with no intermediate liquid stage The nucleus rotates every 52 hours, and its day side is far more active than its night side. The gases ejected from the nucleus are 80 percent water vapour, 17 percent carbon monoxide and 3–4 percent carbon dioxide^[23] with traces of hydrocarbons. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single ^[24]

The nucleus is covered with a layer of dust, which retains heat. Each large dust grain is thought to consist of many tiny particles with spaces in between. Some of these spaces are filled with ice, and others are empty. When Halley's comet is closest to the Sun, temperatures can rise to about 77 °C. Near the Sun, several tons of gas and dust are emitted each second in the jets. Halley has several shallow craters which are about 1 km in diameter.

Meteor showers

Orionid meteor striking the sky below the Milky Way and to the right of Venus. The Orionids are an annual meteor shower, named after their radiant which occurs in the Constellation Orion. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University Zodiacal light is also seen at the image. The zodiacal light is a faint roughly triangular whitish glow seen in the night sky which appears to extend up from the vicinity of the Sun along the Ecliptic

Because its orbit comes close to Earth's orbit in two places, Comet Halley is the parent body of two meteor showers: the Eta Aquarids in early May, and the Orionids in late October. A meteor shower, some of which are known as a "meteor storm" or "meteor outburst" is a celestial event where a group of meteors are observed to radiate from one point The Eta Aquarids are a Meteor shower associated with Halley's Comet. The Orionids are an annual meteor shower, named after their radiant which occurs in the Constellation Orion. ^[25] The Eta Aquarids show orbital similarites approaching Earth as they do of Mars and so a meteor shower at Mars is anticipated there as well^[26] but this time appearing to come from Lambda Gemini.

Designation

This table sets out the astronomical designation for various apparitions of Halley's Comet. A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail —  ^[27][28] For example, "(1P/1982 U1, 1986 III, 1982i" indicates that for the perihelion in 1986, Halley's Comet was the first period comet known (designated 1P) and this apparition was the first seen in "half-month" U (the first half of November) 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). Year 1986 ( MCMLXXXVI) was a Common year starting on Wednesday (link displays 1986 Gregorian calendar) A provisional designation in astronomy is the naming convention applied to Astronomical objects immediately following their discovery The perihelion dates of each apparition are shown. ^[29] The perihelion dates farther from the present are approximate, mainly because of uncertainties in the modeling of non-gravitational effects.

Note that perihelion dates 1607 and later are in the Gregorian calendar, while perihelion dates of 1531 and earlier are in the Julian calendar. Events 1085 - Alfonso VI of Castile takes Toledo Spain back from the Moors. Events By place Carthage Two of Carthage 's Mercenary commanders — Spendius and Mathos — convince the Events 764 - Tibetan troops occupy Chang'an, the capital of the Chinese Tang Dynasty, for fifteen days Events 1538 - Bogotá, Colombia, is founded by Gonzalo Jiménez de Quesada. Year 87 BC was a year of the pre-Julian calendar. Events By place Rome Lucius Cornelius Cinna is elected Consul Events 680 - Battle of Karbala: Shia Imam Husayn bin Ali, the grandson of the Prophet Muhammad, is decapitated Events 41 - After a night of negotiation Claudius is accepted as Roman Emperor by the Senate Year 66 was a Common year starting on Wednesday (link will display the full calendar of the Julian calendar. Events 238 - Gordian I and his son Gordian II are proclaimed Roman emperor. Events 1521 - Edward Stafford 3rd Duke of Buckingham, is executed for Treason. Events By Place Roman Empire May 16 — Elagabalus is declared Roman Emperor Events 1303 - The University of Rome La Sapienza is instituted by Pope Boniface VIII. Events By Place Asia Tuoba Yi Tuo becomes a chieftain of the Chinese Tuoba tribe Events 1249 - Andrew of Longjumeau is dispatched by Louis IX of France as his ambassador to meet with the Khan of the Mongols Events By Place The Americas May 4 — Spearthrower Owl becomes emperor of Teotihuacan. Events 1098 - Fighters of the First Crusade defeat Kerbogha of Mosul. Events By Place Western Roman Empire April 7 — The Huns sack Metz. Events 489 - Odoacer attacks Theodoric at the Battle of Verona and is defeated again For the California area code see Area code 530 Events By Place Byzantine Empire Battle of Daras: Events 44 BC - Julius Caesar, Dictator of the Roman Republic, is stabbed to death by Marcus Junius Brutus, Events By Place Europe Ceolwulf of Wessex fights the South Saxons. Events 1187 - Siege of Jerusalem: Saladin captures Jerusalem after 88 years of Crusader rule Events By Place Asia Wu Ze Tian takes power in China The Ummayad caliph Muawiya II is succeeded by Events 325 - The First Council of Nicaea &ndash the first Ecumenical Council of the Christian Church is held Events By Place Americas The Maya city of Dos Pilas is abandoned Events 202 BC - coronation ceremony of Liu Bang as Emperor Gaozu of Han takes place initiating four centuries of the Han Dynasty 's rule Events By Place Europe Pietro Tradonico is elected Doge of Venice. Events 390 BC - Roman - Gaulish Wars Battle of the Allia - a Roman army is defeated by raiding Gauls, For the automobile see Porsche 912. Events By Place Europe Orso II Participazio becomes the Doge of Events 1590 - Alexander Farnese 's army forces Henry IV of France to raise the siege of Paris. Events By Topic Education Sankore University is founded in Timbuktu. Events 1600 - The Linköping Bloodbath takes place on Maundy Thursday in Linköping, Sweden. Events 1025 - Bolesław Chrobry is crowned in Gniezno, becoming the first King of Poland. Events 48 BC - Pompey the Great is assassinated on orders of King Ptolemy of Egypt after landing in Egypt. Events 1147 - The Portuguese, under Afonso I, and Crusaders from England and Flanders conquer Lisbon after a Events 1444 - Battle of Varna: The crusading forces of King Vladislaus III of Varna (aka Ulaszlo I of Hungary and Wladyslaw Events 53 - Roman Emperor Nero marries Claudia Octavia 62 - Claudia Octavia commits Events 1071 - Battle of Manzikert: The Seljuk Turks defeat the Byzantine Army at Manzikert. Events 312 - Constantine the Great is said to have received his famous Vision of the Cross. Events 668 - Eastern Roman Emperor Constans II is assassinated in his bath at Syracuse Italy. Events 1138 - Cardinal Gregorio Conti is elected Antipope as Victor IV, succeeding Anacletus II. Year 1759 ( MDCCLIX) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common year Events 534 - A second and final revision of the Codex Justinianus is published Year 1835 ( MDCCCXXXV) was a Common year starting on Thursday (link will display the full calendar of the Gregorian Calendar (or a Common Events 1303 - The University of Rome La Sapienza is instituted by Pope Boniface VIII. Year 1910 ( MCMX) was a Common year starting on Saturday (link will display calendar of the Gregorian calendar (or a Common year starting Events 474 - Zeno crowned as co-emperor of the Byzantine Empire. Year 1986 ( MCMLXXXVI) was a Common year starting on Wednesday (link displays 1986 Gregorian calendar) Events 1540 - Thomas Cromwell is executed at the order of Henry VIII of England on charges of Treason. Notable predictions and known events 2061 Expected expiration of the Singapore-Malaysia Water Agreement. The Gregorian calendar is the most widely used Calendar in the world today The Julian calendar, a reform of the Roman calendar, was introduced by Julius Caesar in 46 BC and came into force in 45 BC (709 Ab urbe condita ^[30]

External links

• Comet Halley nucleus by Giotto spacecraft
• cometography.com
• seds.org
• Orbital simulation from JPL (Java) / Ephemeris
• Donald Yeomans, "Great Comets in History"
• Vega 2 Images of Comet Halley

References

Footnotes