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107-506: Comet Hyakutake ( formally designated C/1996 B2 (Hyakutake) ) is a comet discovered on 31 January 1996. It was dubbed the Great Comet of 1996 ; its passage to within 0.1  AU (15 Gm) of the Earth on 25 March was one of the closest cometary approaches of the previous 200 years. Reaching an apparent visual magnitude of zero and spanning nearly 80°, Hyakutake appeared very bright in

214-412: A dwarf planet . When the object is found around a minor planet, the identifier used is the latter's number in parentheses. Thus, Dactyl , the moon of 243 Ida , was at first designated " S/1993 (243) 1 ". Once confirmed and named, it became (243) Ida I Dactyl . Similarly, the fourth satellite of Pluto, Kerberos , discovered after Pluto was categorized as a dwarf planet and assigned a minor planet number,

321-516: A full moon (half a degree) every 30 minutes. Observers estimated its magnitude as around 0, and tail lengths of up to 80 degrees were reported. Its coma, now close to the zenith for observers at mid-northern latitudes , appeared approximately 1.5 to 2 degrees across, roughly four times the diameter of the full moon. The comet's head appeared distinctly blue-green, possibly due to emissions from diatomic carbon (C 2 ) combined with sunlight reflected from dust grains. Because Hyakutake

428-463: A precovery image of the comet was found on a photograph taken on January 1, when the comet was about 2.4 AU from the Sun and had a magnitude of 13.3. When the first calculations of the comet's orbit were made, scientists realized that it was going to pass just 0.1 AU from Earth on 25 March. Only four comets in the previous century had passed closer. Comet Hale–Bopp was already being discussed as

535-405: A Greek-born astronomer working at Meudon , France. However, the age of space probes brought high-resolution images of various Solar System bodies, and it became necessary to propose naming standards for the features seen on them. Initially, the names given to minor planets followed the same pattern as the other planets: names from Greek or Roman myths, with a preference for female names. With

642-426: A capitalized A. Its companions are labelled B, C, and so on. For example, Sirius , the brightest star in the sky, is actually a double star, consisting of the naked-eye visible Sirius A and its dim white-dwarf companion Sirius B . The first exoplanet tentatively identified around the second brightest star in the triple star system Alpha Centauri is accordingly called Alpha Centauri Bb . If an exoplanet orbits both of

749-426: A change in the direction and strength of the local magnetic field . This implied that the spacecraft had crossed the 'wake' of an object, most likely a comet; the object responsible was not immediately identified. In 2000, two teams independently analyzed the same event. The magnetometer team realized that the changes in the direction of the magnetic field mentioned above agreed with the "draping" pattern expected in

856-424: A comet's ion, or plasma tail. The magnetometer team looked for likely suspects. No known comets were located near the satellite, but looking further afield, they found that Hyakutake, 500 million km (3.3 AU) away, had crossed Ulysses ' orbital plane on 23 April 1996. The solar wind had a velocity at the time of about 750 km/s (470 mi/s), at which speed it would have taken eight days for

963-565: A counterclockwise pattern. Hurricanes and tropical storms (massive low-pressure systems) spin counterclockwise in the Northern Hemisphere. The shadow of a sundial moves clockwise on latitudes north of the subsolar point and anticlockwise to the south. During the day at these latitudes, the Sun tends to rise to its maximum at a southerly position. Between the Tropic of Cancer and the Equator,

1070-525: A dust tail in addition to the gas tail seen as it passed the Earth. By this time, however, it was close to the Sun and was not seen as easily. It was observed passing perihelion by the SOHO Sun-observing satellite , which also recorded a large coronal mass ejection being formed at the same time. The comet's distance from the Sun at perihelion was 0.23 AU, well inside the orbit of Mercury . After its perihelion passage, Hyakutake faded rapidly and

1177-465: A history of how some of the major satellites got their current names. The Roman numbering system arose with the very first discovery of natural satellites other than Earth's: Galileo referred to the Galilean moons as I through IV (counting from Jupiter outward), in part to spite his rival Simon Marius , who had proposed the names now adopted, after his own proposal to name the bodies after members of

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1284-407: A more consistent brightening pattern. Thus, all indications suggested Comet Hyakutake would be bright. Besides approaching close to Earth, the comet would also be visible throughout the night to northern hemisphere observers at its closest approach because of its path, passing very close to the pole star . This would be an unusual occurrence, because most comets are close to the Sun in the sky when

1391-634: A number and the Latin genitive of the constellation the star lies in. Examples include 51 Pegasi and 61 Cygni . About 2,500 stars are catalogued. They are commonly used when no Bayer designation exists, or when the Bayer designation uses numeric superscripts such as in Rho¹ ;Cancri . In this case, the simpler Flamsteed designation, 55 Cancri , is often preferred. Most modern catalogues are generated by computers, using high-resolution, high-sensitivity telescopes, and as

1498-429: A number of systematic naming systems for objects of various sorts. There are no more than a few thousand stars that appear sufficiently bright in Earth's sky to be visible to the naked eye . This represents the number of stars available to be named by ancient cultures. The upper boundary to what is physiologically possible to be seen with the unaided eye is an apparent magnitude of 6, or about ten thousand stars. With

1605-409: A possible " great comet "; the astronomical community eventually realised that Hyakutake might also become spectacular because of its close approach. Moreover, Comet Hyakutake's orbit meant that it had last been to the inner Solar System approximately 17,000 years earlier. Because it had probably passed close to the Sun several times before, the approach in 1996 would not be a maiden arrival from

1712-487: A result describe very large numbers of objects. For example, the Guide Star Catalog II has entries on over 998 million distinct astronomical objects. Objects in these catalogs are typically located with very high resolution, and assign designations to these objects based on their position in the sky. An example of such a designation is SDSSp J153259.96−003944.1 , where the initialism SDSSp indicates that

1819-708: A result of the NameExoWorlds campaign in December 2015 the IAU approved the names Cervantes (honoring the writer Miguel de Cervantes ) and Copernicus (honoring the astronomer Nicolaus Copernicus ) for the stars Mu Arae and 55 Cancri A , respectively. In July 2016, the IAU WGSN approved the name Cor Caroli ( Latin for 'heart of Charles') for the star Alpha Canum Venaticorum , so named in honour of King Charles I of England by Sir Charles Scarborough , his physician. In 2019, IAU held

1926-474: A sequential number is assigned by the Minor Planet Center to the minor-planet designation . After the designation is assigned, the discoverer is given an opportunity to propose a name, which, if accepted by the IAU, replaces the provisional designation. Thus for instance, (28978) 2001 KX 76 was given the name Ixion and is now called 28978 Ixion . The name becomes official after its publication in

2033-446: A set of generic rules for the data formats used. The IAU does not recognize the commercial practice of selling fictitious star names by commercial star-naming companies . There are about 300 to 350 stars with traditional or historical proper names. They tend to be the brightest stars in the sky and are often the most prominent ones of the constellation . Examples are Betelgeuse , Rigel and Vega . Most such names are derived from

2140-547: A trans-Plutonian planet. Derived from Classical mythology , these names are only considered standard in Western discussion of the planets. Astronomers in societies that have other traditional names for the planets may use those names in scientific discourse. For instance, IAU does not disapprove of astronomers discussing Jupiter in Arabic using the traditional Arabic name for the planet, المشتري Al-Mushtarīy . Some sixty years after

2247-623: Is especially prevalent in science fiction where the adjective "terran" is also used in the way which "Lunar" or "Jovian" is for Earth's moon or Jupiter. The Latin convention derives from the use of that language as an international scientific language by the first modern astronomers like Copernicus, Kepler, Galileo, Newton and others and was used for a long time. This is why the later discovered bodies were also named accordingly. Two more bodies that were discovered later, and considered planets when discovered, are still generally considered planets now: These were given names from Greek or Roman myth, to match

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2354-494: Is followed by the pulsar's right ascension and degrees of declination . The right ascension is also prefixed with a "J" ( Julian epoch ) or a "B" ( Besselian Epochs ) used prior to 1993, as in PSR B1257+12 . Black holes have no consistent naming conventions. Supermassive black holes receive the designation of the galaxy whose core they reside in. Examples are NGC 4261 , NGC 4151 and M31 , which derive their designation from

2461-435: Is formed by the standard prefix "SN", the year of discovery, and a suffix composed of one to three letters of the Latin alphabet. The first 26 supernovae of the year receive a capital letter from A to Z . Subsequent supernovae of that year are designated with pairs of lower-case letters from "aa" to "az", and then continuing with "ba" until "zz". Then come "aaa", "aab", and so on (this first occurred in 2015-2016). For example,

2568-469: Is named after its first independent discoverers, up to a maximum of three names, separated by hyphens. The IAU prefers to credit at most two discoverers, and it credits more than three discoverers only when "in rare cases where named lost comets are identified with a rediscovery that has already received a new name." In recent years, many comets have been discovered by instruments operated by large teams of astronomers, and in this case, comets may be named for

2675-619: Is taken as the period from the December solstice (typically December 21 UTC ) to the March equinox (typically March 20 UTC), while summer is taken as the period from the June solstice through to the September equinox (typically on 23 September UTC). The dates vary each year due to the difference between the calendar year and the astronomical year . Within the Northern Hemisphere, oceanic currents can change

2782-448: Is to ensure that names assigned are unambiguous. There have been many historical star catalogues , and new star catalogues are set up on a regular basis as new sky surveys are performed. All designations of objects in recent star catalogues start with an "initialism", which is kept globally unique by the IAU. Different star catalogues then have different naming conventions for what goes after the initialism, but modern catalogs tend to follow

2889-413: Is typically referred to simply as "the Sun" or its equivalent in the language being used (for instance, if two astronomers were speaking French, they would call it le Soleil ). However, it is usually called by its Latin name, Sol, in science fiction. There are about two dozen stars such as Barnard's Star and Kapteyn's Star that have historic names and which were named in honor after astronomers . As

2996-422: Is used for planetary rings. These designations are sometimes written like "S/2003 S1", dropping the second space. The letter following the category and year identifies the planet ( J upiter, S aturn, U ranus, N eptune; although no occurrence of the other planets is expected, Mars and Mercury are disambiguated through the use of H ermes for the latter). Pluto was designated by P prior to its recategorization as

3103-561: The New General Catalogue and the list of Messier objects . Other black holes, such as Cygnus X-1 – a highly likely stellar black hole , are cataloged by their constellation and the order in which they were discovered. A large number of black holes are designated by their position in the sky and prefixed with the instrument or survey that discovered them. Examples are SDSS J0100+2802 (where SDSS stands for Sloan Digital Sky Survey ), and RX J1131−1231 , observed by

3210-628: The Arabic language (see List of Arabic star names § History of Arabic star names ) . Stars may have multiple proper names, as many different cultures named them independently. Polaris , for example, has also been known by the names Alruccabah , Angel Stern, Cynosura , the Lodestar , Mismar , Navigatoria , Phoenice , the Pole Star , the Star of Arcady , Tramontana and Yilduz at various times and places by different cultures in human history. In 2016,

3317-500: The Chandra X-ray Observatory . Supernova discoveries are reported to the IAU's Central Bureau for Astronomical Telegrams and are automatically given a provisional designation based on the co-ordinates of the discovery. Historically, when supernovae are identified as belonging to a "type", CBAT has also published circulars with assigned year–letter designations, and discovery details. A supernova's permanent designation

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3424-459: The IAU President and General Secretary. Minor planets observed over at least two nights and which cannot be identified with an existing celestial object, are initially assigned provisional designations (containing the year and the sequential order of discovery within that year) by the Minor Planet Center. When enough observations of the same object are obtained to calculate a reliable orbit,

3531-617: The IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN (on 30 June and 20 July 2016) together with names of stars adopted by the IAU Executive Committee Working Group on Public Naming of Planets and Planetary Satellites during the 2015 NameExoWorlds campaign and recognized by

3638-453: The Medici family failed to win currency. Similar numbering schemes naturally arose with the discovery of moons around Saturn and Mars. Although the numbers initially designated the moons in orbital sequence, new discoveries soon failed to conform with this scheme (e.g. "Jupiter V" is Amalthea , which orbits closer to Jupiter than does Io ). The unstated convention then became, at the close of

3745-523: The Messier catalog has 110 in total. The Andromeda Galaxy is Messier object 31, or M31 ; the Whirlpool Galaxy is M51 . The New General Catalogue (NGC, J. L. E. Dreyer 1888) was much larger and contained nearly 8,000 objects, still mixing galaxies with nebulas and star clusters. The brightest planets in the sky have been named from ancient times. The scientific names are taken from the names given by

3852-466: The NameExoWorlds campaign. With the advent of the increased light-gathering abilities of the telescope, many more stars became visible, far too many to all be given names. Instead, they have designations assigned to them by a variety of different star catalogues . Older catalogues either assigned an arbitrary number to each object, or used a simple systematic naming scheme based on the constellation

3959-460: The Northern temperate zone . The changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. However, a temperate climate can have very unpredictable weather. Tropical regions (between the Tropic of Cancer and the Equator, 0° latitude) are generally hot all year round and tend to experience a rainy season during the summer months, and a dry season during

4066-464: The Oort cloud , a place from where comets with orbital periods of millions of years come. Comets entering the inner Solar System for the first time may brighten rapidly before fading as they near the Sun, because a layer of highly volatile material evaporates. This was the case with Comet Kohoutek in 1973; it was initially touted as potentially spectacular, but only appeared moderately bright. Older comets show

4173-529: The Solar System , north is defined as being in the same celestial hemisphere relative to the invariable plane of the Solar System as Earth's North Pole . Due to Earth's axial tilt of 23.439281°, there is a seasonal variation in the lengths of the day and night. There is also a seasonal variation in temperatures, which lags the variation in day and night. Conventionally, winter in the Northern Hemisphere

4280-475: The WGSBN Bulletin with a brief citation explaining its significance. This may be a few years after the initial sighting, or in the case of "lost" asteroids , it may take several decades before they are spotted again and finally assigned a designation. If a minor planet remains unnamed ten years after it has been given a designation, the right to name it is given also to identifiers of the various apparitions of

4387-547: The celestial sphere belongs to a particular constellation. Like stars, most galaxies do not have names. There are a few exceptions such as the Andromeda Galaxy , the Whirlpool Galaxy , and others, but most simply have a catalog number. In the 19th century, the exact nature of galaxies was not yet understood, and the early catalogs simply grouped together open clusters , globular clusters , nebulas , and galaxies:

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4494-418: The giant planets has increased this period to 70,000 years. This is the first comet to have an X-ray emission detected, which is most likely the result of ionised solar wind particles interacting with neutral atoms in the coma of the comet. The Ulysses spacecraft fortuitously crossed the comet's tail at a distance of more than 500 million km (3.3 AU; 310 million mi) from

4601-566: The last glacial period ended about 10,000 years ago. Earth is currently in an interglacial period of the Quaternary , called the Holocene . The glaciations that occurred during the glacial period covered many areas of the Northern Hemisphere. The Arctic is a region around the North Pole (90° latitude ). Its climate is characterized by cold winters and cool summers. Precipitation mostly comes in

4708-424: The nucleus , showing that Hyakutake had the longest tail known for a comet. The comet was discovered on 30 January 1996, by Yuji Hyakutake , an amateur astronomer from southern Japan. He had been searching for comets for years and had moved to Kagoshima Prefecture partly for the dark skies in nearby rural areas. He was using a powerful set of binoculars with 150 mm (6 in) objective lenses to scan

4815-483: The westerlies , push the currents back to the east, producing a closed clockwise loop. Its surface is 60.7% water, compared with 80.9% water in the case of the Southern Hemisphere , and it contains 67.3% of Earth's land. The continents of North America and mainland Eurasia are located entirely in the Northern Hemisphere, together with about two-thirds of Africa and a small part of South America . During

4922-466: The 19th century, that the numbers more or less reflected the order of discovery, except for prior historical exceptions (see the Timeline of discovery of Solar System planets and their moons ). In addition to naming planets and satellites themselves, the individual geological and geographical features such as craters, mountains, and volcanoes, on those planets and satellites also need to be named. In

5029-506: The 2.5 million years of the Pleistocene , numerous cold phases called glacials ( Quaternary ice age ), or significant advances of continental ice sheets, in Europe and North America , occurred at intervals of approximately 40,000 to 100,000 years. The long glacial periods were separated by more temperate and shorter interglacials which lasted about 10,000–15,000 years. The last cold episode of

5136-557: The Romans: Mercury , Venus , Mars , Jupiter , and Saturn . Our own planet is usually named in English as Earth , or the equivalent in the language being spoken (for instance, two astronomers speaking French would call it la Terre ). However, it is only recently in human history that it has been thought of as a planet. Earth, when viewed as a planet, is sometimes also called by its Latin scientific conventional name Terra , this name

5243-689: The Southern Cross, Epsilon Carinae ( ε Car ) in Carina, Lambda Scorpii ( λ Sco ) in Scorpius and Sigma Sagittarii ( σ Sgr ) in Sagittarius. After all twenty-four Greek letters have been assigned, upper and lower case Latin letters are used, such as for A Centauri ( A Cen ), D Centauri ( D Cen ), G Scorpii ( G Sco ), P Cygni ( P Cyg ), b Sagittarii ( b Sgr ), d Centauri ( d Cen ) and s Carinae ( s Car ). As

5350-704: The Sun can be seen to the north, directly overhead, or to the south at noon, depending on the time of year. In the Southern Hemisphere, the midday Sun is predominantly in the north. When viewed from the Northern Hemisphere, the Moon appears inverted compared to a view from the Southern Hemisphere. The North Pole faces away from the Galactic Center of the Milky Way . This results in the Milky Way being sparser and dimmer in

5457-449: The Sun, which would have evaporated these volatile molecules. Hyakutake's ices must have formed at temperatures of 20  K or less, indicating that it probably formed in a denser-than-average interstellar cloud. The amount of deuterium in the comet's water ices was determined through spectroscopic observations. It was found that the ratio of deuterium to hydrogen (known as the D/H ratio)

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5564-507: The WGSBN has officially limited naming to a maximum of two names per discoverer every two months. Thus, the overwhelming majority of asteroids currently discovered are not assigned formal names. Under IAU rules, names must be pronounceable, preferably one word (such as 5535 Annefrank ), although exceptions are possible (such as 9007 James Bond ), and since 1982, names are limited to a maximum of 16 characters, including spaces and hyphens. (This rule

5671-449: The WGSN. Further batches of names were approved on 21 August 2016, 12 September 2016 and 5 October 2016. These were listed in a table included in the WGSN's second bulletin issued in October 2016. The next additions were done on 1 February, 30 June, 5 September and 19 November 2017, and on 6 June 2018. All are included on the current List of IAU-approved Star Names. The star nearest to Earth

5778-507: The advent of the increased light-gathering abilities of the telescope, many more stars became visible, far too many to all be given names. The earliest naming system which is still popular is the Bayer designation using the name of constellations to identify the stars within them. The IAU is the only internationally recognized authority for assigning astronomical designations to celestial objects and surface features on them. The purpose of this

5885-771: The ancient planet names—but only after some controversy. For example, Sir William Herschel discovered Uranus in 1781, and originally called it Georgium Sidus (George's Star) in honour of King George III of the United Kingdom . French astronomers began calling it Herschel before German Johann Bode proposed the name Uranus, after the Greek god. The name "Uranus" did not come into common usage until around 1850. Starting in 1801, asteroids were discovered between Mars and Jupiter. The first few ( Ceres , Pallas , Juno , Vesta ) were initially considered planets. As more and more were discovered, they were soon stripped of their planetary status. On

5992-461: The beginning of March, rising to 3 × 10 kg/s as the comet approached perihelion. During the same period, dust ejection velocities increased from 50 m/s to 500 m/s. Observations of material being ejected from the nucleus allowed astronomers to establish its rotation period. As the comet passed the Earth, a large puff or blob of material was observed being ejected in the sunward direction every 6.23 hours. A second smaller ejection with

6099-472: The chaotic lunar and Martian nomenclatures then current. Much of the work was done by Mary Adela Blagg , and the report Named Lunar Formations by Blagg and Muller (1935), was the first systematic listing of lunar nomenclature. Later, "The System of Lunar Craters, quadrants I, II, III, IV" was published, under the direction of Gerard P. Kuiper . These works were adopted by the IAU and became the recognized sources for lunar nomenclature. The Martian nomenclature

6206-408: The comet's orbit predict it will not return to the inner Solar System again for approximately 70,000 years. The Ulysses spacecraft made an unexpected pass through the tail of the comet on 1 May 1996. Evidence of the encounter was not noticed until 1998. Astronomers analysing old data found that Ulysses ' instruments had detected a large drop in the number of protons passing, as well as

6313-408: The comets are at their brightest, leading to the comets appearing in a sky not completely dark. Hyakutake became visible to the naked eye in early March 1996. By mid-March, the comet was still fairly unremarkable, shining at 4th magnitude with a tail about 5  degrees long. As it neared its closest approach to Earth, it rapidly became brighter, and its tail grew in length. By March 24, the comet

6420-401: The constellation's name is plural (see genitive case for constellations ) . In addition, a three-letter abbreviation is often used . Examples include Alpha Andromedae ( α And ) in the constellation of Andromeda, Alpha Centauri ( α Cen ), in the constellation Centaurus, Alpha Crucis ( α Cru ) and Beta Crucis ( β Cru ), the two brightest stars in the constellation Crux,

6527-453: The crescent pointing away from the Sun. The cause of the X-ray emission is thought to be a combination of two mechanisms. Interactions between energetic solar wind particles and cometary material evaporating from the nucleus is likely to contribute significantly to this effect. Reflection of solar X-rays is seen in other Solar System objects such as the Moon , but a simple calculation assuming even

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6634-456: The designation is from the " Sloan Digital Sky Survey preliminary objects", and the other characters indicate celestial coordinates ( epoch 'J', right ascension 15 32 59.96 , declination −00°39′44.1″). Variable stars are assigned designations in a variable star scheme that is based on a variation of the Bayer designation format, with an identifying label preceding the Latin genitive of

6741-404: The designations usually consists of a proper noun or abbreviation that often corresponds to the star's name, followed by a lowercase letter (starting with 'b'), like 51 Pegasi b . The lowercase lettering style is drawn from the IAU's long-established rules for naming binary and multiple star systems. A primary star, which is brighter and typically bigger than its companion stars, is designated by

6848-404: The discovery in 1898 of the first body found to cross the orbit of Mars, a different choice was deemed appropriate, and 433 Eros was chosen. This started a pattern of female names for main-belt bodies and male names for those with unusual orbits. As more and more discoveries were made over the years, this system was eventually recognized as being inadequate and a new one was devised. Currently,

6955-448: The discovery of Pluto, a large number of large trans-Neptunian objects began to be discovered. Under the criteria of classifying these Kuiper belt objects (KBOs), it became dubious whether Pluto would have been considered a planet had it been discovered in the 1990s. Its mass is now known to be much smaller than once thought and, with the discovery of Eris , it is simply one of the two largest known trans-Neptunian objects. In 2006, Pluto

7062-437: The early 21st century, hundreds of supernovae were reported every year to the IAU, with more than 500 catalogued in 2007. Since then, the number of newly discovered supernovae has increased to thousands per year, for example almost 16,000 supernovae observations were reported in 2019, more than 2,000 of which were named by CBAT. The sky was divided into constellations by historic astronomers, according to perceived patterns in

7169-423: The early days, only a very limited number of features could be seen on other Solar System bodies other than the Moon . Craters on the Moon could be observed with even some of the earliest telescopes, and 19th-century telescopes could make out some features on Mars. Jupiter had its famous Great Red Spot , also visible through early telescopes. In 1919, the IAU was formed, and it appointed a committee to regularize

7276-523: The first, Hyakutake reported his observation to the National Astronomical Observatory of Japan the following morning. Later that day, the discovery was confirmed by independent observations. At the time of its discovery, the comet was shining at magnitude 11.0 and had a coma approximately 2.5  arcminutes across. It was approximately 2  astronomical units (AU) from the Sun . Later,

7383-630: The form of snow. Areas inside the Arctic Circle (66°34′ latitude) experience some days in summer when the Sun never sets, and some days during the winter when it never rises. The duration of these phases varies from one day for locations right on the Arctic Circle to several months near the Pole, which is the middle of the Northern Hemisphere. Between the Arctic Circle and the Tropic of Cancer (23°26′ latitude) lies

7490-501: The highest X-ray reflectivity possible per molecule or dust grain is not able to explain the majority of the observed flux from Hyakutake, as the comet's atmosphere is very tenuous and diffuse. Observations of comet C/1999 S4 (LINEAR) with the Chandra satellite in 2000 determined that X-rays observed from that comet were produced predominantly by charge exchange collisions between highly charged carbon , oxygen and nitrogen minor ions in

7597-457: The hyphen was replaced by a space. The spaces, apostrophes and other characters in discoverer names are preserved in comet names, like 32P/Comas Solà , 6P/d'Arrest , 53P/Van Biesbroeck , Comet van den Bergh (1974g) , 66P/du Toit , or 57P/du Toit–Neujmin–Delporte . Northern hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator . For other planets in

7704-454: The inner Solar System was the discovery that it was emitting X-rays , with observations made using the ROSAT satellite revealing very strong X-ray emission. This was the first time a comet had been seen to do so, but astronomers soon found that almost every comet they looked at was emitting X-rays. The emission from Hyakutake was brightest in a crescent shape surrounding the nucleus with the ends of

7811-472: The instrument (for example, Comet IRAS–Araki–Alcock (C/1983 H1) was discovered independently by the IRAS satellite and amateur astronomers Genichi Araki and George Alcock ). Comet 105P/Singer Brewster , discovered by Stephen Singer-Brewster , should by rights have been named "105P/Singer-Brewster", but this could be misinterpreted as a joint discovery by two astronomers named Singer and Brewster, respectively, so

7918-533: The name of the constellation in which the star lies. Such designations mark them as variable stars. Examples include R Cygni , RR Lyrae , and V1331 Cygni . The International Astronomical Union delegates the task to the Sternberg Astronomical Institute in Moscow, Russia. Pulsars such as PSR J0737-3039 , are designated with a "PSR" prefix, that stands for Pulsating Source of Radio . The prefix

8025-406: The night sky and was widely seen around the world. The comet temporarily upstaged the much anticipated Comet Hale–Bopp , which was approaching the inner Solar System at the time. Hyakutake is a long-period comet that passed perihelion on 1 May 1996. Before its most recent passage through the Solar System, its orbital period was about 17,000 years, but the gravitational perturbation of

8132-427: The nucleus ( Halley's Comet is about 15 km (9.3 mi) across, while Comet Hale–Bopp was about 60 km (37 mi) across) implies that Hyakutake must have been very active to become as bright as it did. Most comets undergo outgassing from a small proportion of their surface, but most or all of Hyakutake's surface seemed to have been active. The dust production rate was estimated to be about 2 × 10 kg/s at

8239-525: The object, to discoverers at apparitions other than the official one, to those whose observations contributed extensively to the orbit determination, or to representatives of the observatory at which the official discovery was made. The WGSBN has the right to act on its own in naming a minor planet, which often happens when the number assigned to the body is an integral number of thousands. In recent years, automated search efforts such as LINEAR or LONEOS have discovered so many thousands of new asteroids that

8346-454: The original discoverer of the comet, Pierre Méchain. Other comets that bore the possessive include "Biela's Comet" ( 3D/Biela ) and "Miss Herschel's Comet" ( 35P/Herschel–Rigollet , or Comet Herschel–Rigollet). Most bright (non-periodic) comets were referred to as 'The Great Comet Of...' the year in which they appeared. In the early 20th century, the convention of naming comets after their discoverers became common, and this remains today. A comet

8453-426: The other hand, Pluto was considered to be a planet at the time of its discovery in 1930, as it was found beyond Neptune. Following this pattern, several hypothetical bodies were given names: Vulcan for a planet within the orbit of Mercury; Phaeton for a planet between Mars and Jupiter that was believed to be the precursor of the asteroids; Themis for a moon of Saturn; and Persephone , and several other names, for

8560-447: The past two centuries. Before any systematic naming convention was adopted, comets were named in a variety of ways. The first one to be named was " Halley's Comet " (now officially known as Comet Halley), named after Edmond Halley , who had calculated its orbit. Similarly, the second known periodic comet, Comet Encke (formally designated 2P/Encke), was named after the astronomer, Johann Franz Encke, who had calculated its orbit rather than

8667-456: The past. Names of people, companies or products known only for success in business are not accepted, nor are citations that resemble advertising. Whimsical names can be used for relatively ordinary asteroids (such as 26858 Misterrogers or 274301 Misplaced Pages ), but those belonging to certain dynamical groups are expected to follow more strictly defined naming schemes. The names given to comets have followed several different conventions over

8774-799: The prominent SN 1987A , was the first one to be observed in 1987, while SN 2023ixf was one of the brightest ever observed in recent times. Several thousand supernovae have been reported since 1885. In recent years, several supernova discovery projects have retained their more distant supernova discoveries for in-house follow-up, and not reported them to CBAT. Starting in 2015, CBAT has scaled back its efforts to publish assigned designations of typed supernovae: By September 2014, CBAT had published names and details of 100 supernovae discovered in that year. By September 2015, CBAT had only published names of 20 supernovae discovered in that year. The Astronomer's Telegram provides some surrogate services independent from CBAT. Four historical supernovae are known simply by

8881-592: The resolving power of telescopes increased, numerous objects that were thought to be a single object were found to be optical star systems that were too closely spaced in the sky to be discriminated by the human eye. This led to a third iteration, where numeric superscripts were added to distinguish those previously unresolved stars. Examples include Theta Sagittarii ( θ Sgr ) later distinguished as Theta¹ Sagittarii ( θ¹ Sgr ) and Theta² Sagittarii ( θ² Sgr ), each being their own (physical) star system with two and three stars, respectively. Flamsteed designations consist of

8988-772: The responsibility for naming minor planets lies with the Working Group Small Bodies Nomenclature (WGSBN, originally the Committee Small Bodies Nomenclature , CSBN, and before that the Minor Planet Names Committee , MPNC), which is composed of 15 members, 11 of whom are voting members, while the other four are representatives for the Working Group for Planetary System Nomenclature , the Minor Planet Center , as well as

9095-431: The same period confirmed this as the rotation period of the nucleus. Astronomical naming conventions#Comets The International Astronomical Union (IAU) is the recognized authority in astronomy for assigning designations to celestial bodies such as stars, planets, and minor planets , including any surface features on them. In response to the need for unambiguous names for astronomical objects, it has created

9202-452: The same time. The relative abundances of chemical elements detected indicated that the object responsible was definitely a comet. Based on the Ulysses encounter, the comet's tail is known to have been at least 570 million km (360 million miles; 3.8 AU) long. This is almost twice as long as the previous longest-known cometary tail, that of the Great Comet of 1843 , which

9309-424: The skies on the night of the discovery. This comet was actually the second Comet Hyakutake; Hyakutake had discovered comet C/1995 Y1 several weeks earlier. While re-observing his first comet (which never became visible to the naked eye ) and the surrounding patch of sky, Hyakutake was surprised to find another comet in almost the same position as the first had been. Hardly believing a second discovery so soon after

9416-417: The sky. At first, only the shapes of the patterns were defined, and the names and numbers of constellations varied from one star map to another. Despite being scientifically meaningless, they do provide useful reference points in the sky for human beings, including astronomers. In 1930, the boundaries of these constellations were fixed by Eugène Joseph Delporte and adopted by the IAU, so that now every point on

9523-483: The solar wind, and neutral water, oxygen and hydrogen in the comet's coma. Radar results from the Arecibo Observatory indicated that the comet nucleus was about 4.8 km (3 mi) across, and surrounded by a flurry of pebble-sized particles ejected at a few metres per second. This size measurement corresponded well with indirect estimates using infrared emission and radio observations. The small size of

9630-563: The star lies in, like the older Ptolemy 's Almagest in Greek from 150 and Al-Sufi 's Book of Fixed Stars in Arabic from 964. The variety of sky catalogues now in use means that most bright stars currently have multiple designations. In 1540, the Italian astronomer Piccolomini released the book De le Stelle Fisse (On the Fixed Stars) which include star maps of 47 constellations where he numbered

9737-433: The stars in a binary system, its name can be, for example, Kepler-34(AB) b . Earth's natural satellite is simply known as the Moon , or the equivalent in the language being spoken (for instance, two astronomers speaking French would call it la Lune ). English-language science fiction often adopts the Latin name "Luna" while using the English "Moon" as a term for natural satellites in general in order to better distinguish

9844-414: The stars in magnitude order using latin letters. The Bayer designations of about 1,500 brightest stars were first published in 1603. In this list, a star is identified by a lower-case letter of the Greek alphabet , followed by the Latin name of its parent constellation. The Bayer designation uses the possessive form of a constellation's name, which in almost every case ends in is , i or ae ; um if

9951-498: The tail to be carried out to where the spacecraft was situated at 3.73 AU, approximately 45 degrees out of the ecliptic plane. The orientation of the ion tail inferred from the magnetic field measurements agreed with the source lying in Comet Hyakutake's orbital plane. The other team, working on data from the spacecraft's ion composition spectrometer, discovered a sudden large spike in detected levels of ionised particles at

10058-448: The weather patterns that affect many factors within the north coast. For the same reason, flows of air down toward the northern surface of the Earth tend to spread across the surface in a clockwise pattern. Thus, clockwise air circulation is characteristic of high pressure weather cells in the Northern Hemisphere. Conversely, air rising from the northern surface of the Earth (creating a region of low pressure) tends to draw air toward it in

10165-457: The weather patterns that affect many factors within the north coast. Such events include El Niño–Southern Oscillation . Trade winds blow from east to west just above the equator. The winds pull surface water with them, creating currents, which flow westward due to the Coriolis effect . The currents then bend to the right, heading north. At about 30 degrees north latitude, a different set of winds,

10272-864: The wider concept from any specific example. Natural satellites of other planets are generally named after mythological figures related to their parent body's namesake, such as Phobos and Deimos , the twin sons of Ares (Mars), or the Galilean moons of Io , Europa , Ganymede , and Callisto , four consorts of Zeus (Jupiter). Satellites of Uranus are instead named after characters from works by William Shakespeare or Alexander Pope , such as Umbriel or Titania . When natural satellites are first discovered, they are given provisional designations such as " S/2010 J 2 " (the 2nd new satellite of Jupiter discovered in 2010) or " S/2003 S 1 " (the 1st new satellite of Saturn discovered in 2003). The initial "S/" stands for "satellite", and distinguishes from such prefixes as "D/", "C/", and "P/", used for comets . The designation "R/"

10379-482: The winter months. In the Northern Hemisphere, objects moving across or above the surface of the Earth tend to turn to the right because of the Coriolis effect . As a result, large-scale horizontal flows of air or water tend to form clockwise-turning gyres . These are best seen in ocean circulation patterns in the North Atlantic and North Pacific oceans. Within the Northern Hemisphere, oceanic currents can change

10486-589: The year they occurred: SN 1006 (the brightest stellar event ever recorded), SN 1054 (of which the remnant is the Crab Nebula and the Crab Pulsar ), SN 1572 ( Tycho's Nova ), and SN 1604 ( Kepler's Star ). Since 1885, the letter-suffixes are explicitly assigned, regardless whether only one supernova is detected during the entire year (although this has not occurred since 1947). Driven by advances in technology and increases in observation time in

10593-423: Was 2 AU long. This record was broken in 2002 by comet 153P/Ikeya–Zhang , which had a tail-length of at least 7.46 AU . Terrestrial observers found ethane and methane in the comet, the first time either of these gases had been detected in a comet. Chemical analysis showed that the abundances of ethane and methane were roughly equal, which may imply that its ices formed in interstellar space, away from

10700-455: Was about 3 × 10, which compares to a value in Earth's oceans of about 1.5 × 10. It has been proposed that cometary collisions with Earth might have supplied a large proportion of the water in the oceans, but the high D–H ratio measured in Hyakutake and other comets such as Hale–Bopp and Halley's Comet have caused problems for this theory. One of the great surprises of Hyakutake's passage through

10807-424: Was at its brightest for only a few days, it did not have time to permeate the public imagination in the way that Comet Hale–Bopp did the following year. Many European observers in particular did not see the comet at its peak because of unfavourable weather conditions. After its close approach to the Earth, the comet faded to about 2nd magnitude. It reached perihelion on 1 May 1996, brightening again and exhibiting

10914-409: Was clarified in 1958, when a committee of the IAU recommended for adoption the names of 128 albedo features (bright, dark, or colored) observed through ground-based telescopes (IAU, 1960). These names were based on a system of nomenclature developed in the late 19th century by the Italian astronomer Giovanni V. Schiaparelli (1879) and expanded in the early 20th century by Eugene M. Antoniadi (1929),

11021-546: Was designated S/2011 (134340) 1 rather than S/2011 P 1, though the New Horizons team, who disagreed with the dwarf planet classification, used the latter. After a few months or years, when a newly discovered satellite's existence has been confirmed and its orbit computed, a permanent name is chosen, which replaces the "S/" provisional designation. However, in the past, some satellites remained unnamed for surprisingly long periods after their discovery. See Naming of moons for

11128-453: Was lost to naked-eye visibility by the end of May. Its orbital path carried it rapidly into the southern skies, but following perihelion it became much less monitored. The last known observation of the comet took place on November 2. Hyakutake had passed through the inner Solar System approximately 17,000 years ago; gravitational interactions with the gas giants during its 1996 passage stretched its orbit greatly, and barycentric fits to

11235-412: Was one of the brightest objects in the night sky, and its tail stretched 35 degrees. The comet had a notably bluish-green colour. The closest approach occurred on 25 March at a distance of 0.1  AU (15 million  km ; 39  LD ). Hyakutake was moving so rapidly across the night sky that its movement could be detected against the stars in just a few minutes; it covered the diameter of

11342-515: Was therefore reclassified into a different class of astronomical bodies known as dwarf planets , along with Eris and others. Currently, according to the IAU, there is no agreed upon system for designating exoplanets (planets orbiting other stars). The process of naming them is organized by the IAU Executive Committee Working Group Public Naming of Planets and Planetary Satellites. The scientific nomenclature for

11449-538: Was violated once for the comet-asteroid 4015 Wilson–Harrington , whose name has 17 characters; this is because it had already been named as a comet before being rediscovered as an asteroid.) Letters with diacritics are accepted, although in English the diacritical marks are usually omitted in everyday usage. 4090 Říšehvězd is an asteroid with the most diacritics (four). Military and political leaders are unsuitable unless they have been dead for at least 100 years. Names of pet animals are discouraged, but there are some from

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