Astronomical naming conventions
Encyclopedia
In ancient times, only the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 and Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

, a few hundred star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s and the most easily visible planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

s had names. Over the last few hundred years, the number of identified astronomical objects has risen from hundreds to over a billion, and more are discovered every year. Astronomers need to be able to assign systematic designations to unambiguously identify all of these objects, and at the same time give names to the most interesting objects and, where relevant, features of those objects.

The International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

 (IAU) is the body officially recognized by astronomers
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

 and other scientists worldwide as the de facto naming authority for astronomical bodies. In response to the need for unambiguous names for astronomical objects, it has created a number of systematic naming
Systematic name
A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection...

 systems for bodies of various sorts.

Names of stars

According to the IAU, apart from a limited number of bright stars with historic names, star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s do not have proper name
Proper name
"A proper name [is] a word that answers the purpose of showing what thing it is that we are talking about" writes John Stuart Mill in A System of Logic , "but not of telling anything about it"...

s. Where historic names exist, these names are, with a few exceptions, taken from the Arabic language
Arabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...

 due to their lead in the beginning of modern astronomy. See List of traditional star names for examples.

There are no more than a few thousand stars that appear sufficiently bright in the Earth's sky to be visible to the naked eye, so this represents the limit of the possible number of stars available to be named by ancient cultures. This limit is approximate, as it varies by the acuity of any given observer's eyes, but ten thousand stars (the naked-eye stars to visual magnitude six) seems to be an upper bound to what is physiologically possible.

Estimates of the number of stars with recognised proper names range from 300 to 350 different stars. These tend to be the brightest stars, or stars that form part of constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 patterns with the brightest stars. The number of proper names for stars is greater than the number of stars with proper names, as many different cultures named stars independently. For example, the star known as Polaris
Polaris
Polaris |Alpha]] Ursae Minoris, commonly North Star or Pole Star, also Lodestar) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star....

 has also at various times and places been known by the names Alruccabah, Angel Stern, Cynosura, the Lodestar, Mismar, Navigatoria, Phoenice, the Pole Star, the Star of Arcady, Tramontana and Yilduz.

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 catalogue
Star catalogue
A star catalogue, or star catalog, is an astronomical catalogue that lists stars. In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different star catalogues which have been produced for different purposes over the years, and this article covers only some...

s. Older catalogues either assigned an arbitrary number to each object, or used a simple systematic naming scheme such as combining constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 names with Greek letters
Greek alphabet
The Greek alphabet is the script that has been used to write the Greek language since at least 730 BC . The alphabet in its classical and modern form consists of 24 letters ordered in sequence from alpha to omega...

. Multiple sky catalogues meant that some stars had more than one designation. For example, the star with the Arabic name of Rigil Kentaurus also has the Bayer designation
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name...

 of Alpha Centauri
Alpha Centauri
Alpha Centauri is the brightest star in the southern constellation of Centaurus...

.

As the resolving power of telescopes increased, numerous objects that were thought to be a single object were found to be multiple star systems that were too closely spaced in the sky to be discriminated by the human eye. These and other confusions make it essential that great care is taken in using designations. For example, Rigil Kentaurus contains three stars in a triple star system, labelled Rigil Kentaurus A, B and C respectively.

Most modern catalogues are generated by computers, using high-resolution, high-sensitivity telescopes, and as 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 the designation is from the "Sloan Digital Sky Survey
Sloan Digital Sky Survey
The Sloan Digital Sky Survey or SDSS is a major multi-filter imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project was named after the Alfred P...

 preliminary objects", and the other characters indicate celestial coordinates.

The star nearest to Earth, our Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

, is typically referred to simply as "the Sun" or its equivalent in the language being used (for instance, if two astronomers were speaking French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

, they would call it le Soleil). However, it is sometimes called by its Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 name, Sol.

Finally, there are a few stars named after people.

Managing the initialisms of star catalogues

The IAU is the ultimate maintainer of the namespace
Namespace
In general, a namespace is a container that provides context for the identifiers it holds, and allows the disambiguation of homonym identifiers residing in different namespaces....

 of astronomical designations in catalogues of astronomical objects. The purpose of this is to ensure that names assigned by these catalogues 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 catalogues tend to follow a set of generic rules for the data formats used.

Star-naming companies

Several for-profit star-naming companies sell the right to list stars in their private registries under whatever name the buyer so chooses. These companies typically disclaim the fact that they are not associated with the scientific community and that such gifts are a novelty and only symbolic in nature. Strong consumer demand for novelty star naming keeps these companies in business even when the customer is well informed. However, the IAU (and, therefore, most astronomers) do not recognize those names as "official". Most astronomical organizations (and most international scientific organizations) say that the IAU is the only body allowed to officially name heavenly objects. (It is important to realize that the companies, in fact, often 'doublebook' prominent stars with each other; and sometimes the same company will assign different names to the same object. The customer, of course, is not informed of any prior claim).

Names and boundaries of constellations

The sky was arbitrarily divided into constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

s by historic astronomers, according to perceived patterns in 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
Eugène Joseph Delporte
Eugène Joseph Delporte was a Belgian astronomer.-Discoveries:He discovered a total of sixty-six asteroids. Notable discoveries include 1221 Amor and the Apollo asteroid 2101 Adonis. He discovered or co-discovered some comets as well, including periodic comet 57P/du Toit-Neujmin-Delporte...

 and adopted by the IAU, so that now every point on the celestial sphere
Celestial sphere
In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with the Earth and rotating upon the same axis. All objects in the sky can be thought of as projected upon the celestial sphere. Projected upward from Earth's equator and poles are the...

 belongs to a particular constellation.

Names of supernovae

Supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...

 discoveries are reported to the International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

's Central Bureau for Astronomical Telegrams
Central Bureau for Astronomical Telegrams
The Central Bureau for Astronomical Telegrams is the official international clearing house for information relating to transient astronomical events....

 which sends out a circular with the name it assigns to it. The name is formed by the year of discovery, immediately followed by a one- or two-letter designation. The first 26 supernovae of the year get an upper case letter from A
A
A is the first letter and a vowel in the basic modern Latin alphabet. It is similar to the Ancient Greek letter Alpha, from which it derives.- Origins :...

to Z
Z
Z is the twenty-sixth and final letter of the basic modern Latin alphabet.-Name and pronunciation:In most dialects of English, the letter's name is zed , reflecting its derivation from the Greek zeta but in American English, its name is zee , deriving from a late 17th century English dialectal...

. Afterward, pairs of lower-case letters are used, starting with aa, ab, and so on. Four historical supernovae are known simply by the year they occurred (SN 1006
SN 1006
SN 1006 was a supernova, widely seen on Earth beginning in the year 1006 AD; Earth was about 7,200 light-years away from the supernova. It was the brightest apparent magnitude stellar event in recorded history reaching an estimated -7.5 visual magnitude...

, 1054
SN 1054
SN 1054 is a supernova that was first observed as a new "star" in the sky on July 4, 1054 AD, hence its name, and that lasted for a period of around two years. The event was recorded in multiple Chinese and Japanese documents and in one document from the Arab world...

, 1572
SN 1572
SN 1572 , "B Cassiopeiae" , or 3C 10 was a supernova of Type Ia in the constellation Cassiopeia, one of about eight supernovae visible to the naked eye in historical records...

 (Tycho's Nova), and 1604
SN 1604
Supernova 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a supernova that occurred in the Milky Way, in the constellation Ophiuchus. , it is the last supernova to have been unquestionably observed in our own galaxy, occurring no farther than 6 kiloparsecs or about...

 (Kepler's Star)); starting with 1885, the letters are used, even if there was only one supernova detected that year (e.g. SN 1885A, 1907A, etc.) —this last happened with SN 1947A. The standard abbreviation "SN" is an optional prefix. As instruments improve and the number of astronomers (both professional and amateur) searching increases, more and more supernovae are observed each year - currently at least 500 a year. For example, the last supernova of 2007 was SN 2007va, indicating that it was the 572nd supernova found in 2007 (a record year, in fact).

Names of galaxies

Like stars, most galaxies do not have names. There are a few exceptions such as the Andromeda Galaxy
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...

, the Whirlpool Galaxy
Whirlpool Galaxy
The Whirlpool Galaxy is an interacting grand-design spiral galaxy that is estimated to be 23 ± 4 million light-years from the Milky Way Galaxy. in the constellation Canes Venatici...

, 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 cluster
Open cluster
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...

s, globular cluster
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...

s, nebula
Nebula
A nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...

s, and galaxies: the Messier catalog has 110 in total. The Andromeda Galaxy is Messier object 31, or M31
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...

; the Whirlpool Galaxy is M51
M51
M51 or M-51 may refer to:* M-51 , a state highway in Michigan* M51 SLBM, a French nuclear ballistic missile* BMW M51, a 1991 straight-6 Diesel engine* Eidgenössischer Stutzer 1851, a historical service rifle of the Swiss Army...

. The New General Catalogue
New General Catalogue
The New General Catalogue of Nebulae and Clusters of Stars is a well-known catalogue of deep sky objects in astronomy. It contains 7,840 objects, known as the NGC objects...

 (NGC, J. L. E. Dreyer 1888) was much larger and contained nearly 8,000 objects, still mixing galaxies with nebulas and star clusters.

Names of planets

The brightest planets in the sky have been named from ancient times. The scientific names are taken from the names given by the Romans: Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...

, Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

, Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

, Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

, and Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...

. Our own planet is usually named the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, or the equivalent in the language being spoken (for instance, two astronomers speaking French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

 would call it la Terre). However, it is only recently in human history that it has been thought of as a planet. The Earth, when viewed as a planet, is sometimes also called by its Latin name Terra (some older science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

 uses the alternate Tellus
Tellus
Tellus is a Latin word meaning "earth" and may refer to:* Terra or Terra Mater, the Roman Earth Mother goddess* Tellus , a citizen of ancient Athens who was thought to be the happiest of men...

).

At least two more bodies were discovered later, and called planets:
  • Uranus
    Uranus
    Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...

    , discovered by William Herschel
    William Herschel
    Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...

     in 1781
  • Neptune
    Neptune
    Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...

    , discovered by Johann Gottfried Galle
    Johann Gottfried Galle
    Johann Gottfried Galle was a German astronomer at the Berlin Observatory who, on 23 September 1846, with the assistance of student Heinrich Louis d'Arrest, was the first person to view the planet Neptune, and know what he was looking at...

     in 1846 (based on predictions by Urbain Le Verrier and John Couch Adams
    John Couch Adams
    John Couch Adams was a British mathematician and astronomer. Adams was born in Laneast, near Launceston, Cornwall, and died in Cambridge. The Cornish name Couch is pronounced "cooch"....

    )


All of these planets were given names from Greek or Roman myth, to match the ancient planet names. However, this was only after some controversy. For example, Sir William Herschel
William Herschel
Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...

 discovered Uranus in 1781, and originally called it Georgium Sidus (George's Star) in honour of King George III of the United Kingdom
George III of the United Kingdom
George III was King of Great Britain and King of Ireland from 25 October 1760 until the union of these two countries on 1 January 1801, after which he was King of the United Kingdom of Great Britain and Ireland until his death...

. French astronomers began calling it Herschel before German Johann Bode proposed the name Uranus, after the Greek and Roman god. The name "Uranus" did not come into common usage until around 1850.

Starting in 1801, asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...

s were discovered between Mars and Jupiter. The first few (Ceres, Pallas
2 Pallas
Pallas, formally designated 2 Pallas, is the second asteroid to have been discovered , and one of the largest. It is estimated to constitute 7% of the mass of the asteroid belt, and its diameter of 530–565 km is comparable to, or slightly larger than, that of 4 Vesta. It is however 20%...

, Juno
3 Juno
Juno , formal designation 3 Juno in the Minor Planet Center catalogue system, was the third asteroid to be discovered and is one of the larger main-belt asteroids, being one of the two largest stony asteroids, along with 15 Eunomia. Juno is estimated to contain 1% of the total mass of the asteroid...

, Vesta
4 Vesta
Vesta, formally designated 4 Vesta, is one of the largest asteroids, with a mean diameter of about . It was discovered by Heinrich Wilhelm Olbers on March 29, 1807, and is named after the Roman virgin goddess of home and hearth, Vesta....

) were initially considered minor planet
Minor planet
An asteroid group or minor-planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid...

s and joined the ranks of the planets. As more and more were discovered, they were soon stripped of their planetary status. On the other hand, Pluto
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...

 was considered to be a planet at the time of its discovery in 1930, as it was found far beyond any then-known asteroid's greatest distance from the Sun.

Following this pattern, several hypothetical bodies were given names:
  • Vulcan
    Vulcan (hypothetical planet)
    Vulcan was a small planet proposed to exist in an orbit between Mercury and the Sun. In an attempt to explain peculiarities of Mercury's orbit, in the 19th-century French mathematician Urbain Jean Joseph Le Verrier hypothesized that they were the result of another planet, which he named Vulcan...

    , for a planet within the orbit of Mercury;
  • Phaeton
    Phaeton (hypothetical planet)
    Phaeton is the name of a hypothetical planet posited to once have existed between the orbits of Mars and Jupiter whose destruction supposedly led to the formation of the asteroid belt...

    , for a planet between Mars and Jupiter which was the precursor of the asteroids;
  • Themis
    Themis (hypothetical moon)
    On April 28, 1905, William H. Pickering, who had seven years earlier discovered Phoebe, announced the discovery of a tenth satellite of Saturn, which he promptly named Themis. The photographic plates on which it supposedly appeared, thirteen in all, spanned a period between April 17 and July 8, 1904...

    , for a moon of Saturn;
  • Persephone (and several other names), for a trans-Plutonian planet.


These names, derived from Classical mythology
Classical mythology
Classical mythology or Greco-Roman mythology is the cultural reception of myths from the ancient Greeks and Romans. Along with philosophy and political thought, mythology represents one of the major survivals of classical antiquity throughout later Western culture.Classical mythology has provided...

, are only considered standard in Western
Western culture
Western culture, sometimes equated with Western civilization or European civilization, refers to cultures of European origin and is used very broadly to refer to a heritage of social norms, ethical values, traditional customs, religious beliefs, political systems, and specific artifacts and...

 discussion of the planets. Astronomers in societies which have alternate traditional names for the planets may use those names in scientific discourse. The IAU does not disapprove astronomers discussing Jupiter in Arabic
Arabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...

 using the term Al-Mushtarīy or astronomers speaking in Mandarin Chinese discussing Neptune referring to the planet as Hǎiwángxīng.

Some sixty years after the discovery of Pluto, a large number of large trans-Neptunian object
Trans-Neptunian object
A trans-Neptunian object is any minor planet in the Solar System that orbits the Sun at a greater distance on average than Neptune.The first trans-Neptunian object to be discovered was Pluto in 1930...

s began to be discovered. Under the criteria of classifying these Kuiper belt
Kuiper belt
The Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 50 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive...

 objects (KBOs), it became dubious whether Pluto would have been called 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
Eris (dwarf planet)
Eris, formal designation 136199 Eris, is the most massive known dwarf planet in the Solar System and the ninth most massive body known to orbit the Sun directly...

, it is simply one of the two largest known trans-Neptunian object. In 2006, Pluto was therefore reclassified to a different class of astronomical bodies known as dwarf planet
Dwarf planet
A dwarf planet, as defined by the International Astronomical Union , is a celestial body orbiting the Sun that is massive enough to be spherical as a result of its own gravity but has not cleared its neighboring region of planetesimals and is not a satellite...

s, along with Eris and others.

Natural satellites of planets

The Earth's moon is simply known as the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

, or the equivalent in the language being spoken (for instance, two astronomers speaking French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

 would call it la Lune). It is sometimes called Luna (which is simply Latin for "moon"). Natural satellites of other planets are generally named after mythological figures. Satellites of Uranus are named after characters from works by William Shakespeare
William Shakespeare
William Shakespeare was an English poet and playwright, widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's national poet and the "Bard of Avon"...

 or Alexander Pope
Alexander Pope
Alexander Pope was an 18th-century English poet, best known for his satirical verse and for his translation of Homer. He is the third-most frequently quoted writer in The Oxford Dictionary of Quotations, after Shakespeare and Tennyson...

.

When satellites are first discovered, they are given provisional designations such as "S/2010 J 2
S/2010 J 2
' is a natural satellite of Jupiter. It was discovered by Christian Veillet in 2010....

" (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 comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...

s. The designation "R/" 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 (Jupiter, Saturn, Uranus, Neptune; although no occurrence of the other planets is expected, Mars and Mercury are disambiguated through the use of Hermes for the latter). Pluto
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...

 was designated by P prior to its recategorization as a dwarf planet
Dwarf planet
A dwarf planet, as defined by the International Astronomical Union , is a celestial body orbiting the Sun that is massive enough to be spherical as a result of its own gravity but has not cleared its neighboring region of planetesimals and is not a satellite...

. 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
243 Ida
243 Ida is an asteroid in the Koronis family of the asteroid belt. It was discovered on 29 September 1884 by Johann Palisa and named after a nymph from Greek mythology. Later telescopic observations categorized Ida as an S-type asteroid, the most numerous type in the inner asteroid belt. On 28...

, was at first designated "S/1993 (243) 1". Once confirmed and named, it became (243) Ida I Dactyl. Similarly, the fourth satellite of Pluto, discovered after Pluto was categorized as a dwarf planet and assigned a minor planet number, is designated S/2011 (134340) 1 rather than S/2011 P 1, though the New Horizon's team, who disagree with the dwarf planet classification, use the latter.
  • H = Mercury
    Mercury (planet)
    Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...

     (Hermes)
  • V = Venus
    Venus
    Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

  • E = Earth
    Earth
    Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

  • M = Mars
    Mars
    Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

  • J = Jupiter
    Jupiter
    Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

  • S = Saturn
    Saturn
    Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...

  • U = Uranus
    Uranus
    Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...

  • N = Neptune
    Neptune
    Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...



Note: The assignation of "H" for Mercury is specified by the USGS Gazetteer of Planetary Nomenclature; since they usually follow IAU guidelines closely, this is very likely the IAU convention, but confirmation is needed.

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 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 Moon: Galileo
Galileo Galilei
Galileo Galilei , was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations and support for Copernicanism...

 referred to the Galilean moons
Galilean moons
The Galilean moons are the four moons of Jupiter discovered by Galileo Galilei in January 1610. They are the largest of the many moons of Jupiter and derive their names from the lovers of Zeus: Io, Europa, Ganymede and Callisto. Ganymede, Europa and Io participate in a 1:2:4 orbital resonance...

 as I through IV (counting from Jupiter outward), in part to spite his rival Simon Marius
Simon Marius
Simon Marius was a German astronomer. He was born in Gunzenhausen, near Nuremberg, but he spent most of his life in the city of Ansbach....

, who had proposed the names now adopted, after his own proposal to name the bodies after members of 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
Amalthea (moon)
Amalthea is the third moon of Jupiter in order of distance from the planet. It was discovered on September 9, 1892, by Edward Emerson Barnard and named after Amalthea, a nymph in Greek mythology. It is also known as '....

, which orbits closer to Jupiter than does Io
Io (moon)
Io ) is the innermost of the four Galilean moons of the planet Jupiter and, with a diameter of , the fourth-largest moon in the Solar System. It was named after the mythological character of Io, a priestess of Hera who became one of the lovers of Zeus....

). The unstated convention then became, at the close of 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).

Geological and geographical features on planets and satellites

In addition to naming planets and satellites themselves, the individual geological and geographical features (craters, mountains, volcanos and so forth) on those planets and satellites also need to be named.

In the early days, only a very limited number of features could be seen on other solar system bodies other than the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

. Craters on the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 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 though early telescopes.

In 1919 the IAU was formed, and it appointed a committee to regularize the chaotic lunar and Martian nomenclatures then current. Much of the work was done by Mary Adela Blagg
Mary Adela Blagg
Mary Adela Blagg was an English astronomer.She was born in Cheadle, Staffordshire, and lived her entire life there. Mary was the daughter of a solicitor, John Charles Blagg, and France Caroline Foottit. She trained herself in mathematics by reading her brother's textbooks...

, 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 was clarified in 1958, when a committee of the IAU recommended for adoption the names of 128 albedo feature
Albedo feature
An albedo feature is a large area on the surface of a planet which shows a contrast in brightness or darkness with adjacent areas....

s (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), a Greek-born astronomer working at Meudon, France.

However, the age of space probe
Space probe
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

s brought high-resolution images of various solar system bodies, and it became necessary to propose naming standards for the features seen on them.

Minor planets

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 the discovery in 1898 of the first body found to cross the orbit of Mars, a different choice was deemed appropriate, and 433 Eros
433 Eros
433 Eros is a near-Earth asteroid discovered in 1898, and the first asteroid to be orbited by a probe . It is an S-type asteroid approximately 34.4×11.2×11.2 km in size, the second-largest NEA after 1036 Ganymed, and belongs to the Amor group.Eros is a Mars-crosser asteroid, the first known...

 was chosen. This started a pattern of female names for main-belt
Asteroid belt
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets...

 bodies and male names for those with unusual orbits.

Over the years as more and more discoveries have been made, this system was eventually recognized as being inadequate and a new one was devised. Currently, the main responsibility for designating and naming minor planets lies on the Committee for Small Body Nomenclature (CSBN).
Minor planet
Minor planet
An asteroid group or minor-planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid...

s are initially assigned provisional designations when observed, of the form "" (the first part is a year; the second part defines a sequential order of discovery within that year, see provisional designation for details). If enough sightings are obtained of the same minor planet to calculate an orbit, the object is assigned a sequential number - its 'designation' - and it can then be cited as, for instance, .

After the designation is assigned, the discoverer is given an opportunity to propose a name, which, if it is accepted by the IAU
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

, replaces the provisional designation. Thus for instance, was given the name Ixion and is now known as (28978) Ixion, which is often abridged to 28978 Ixion
28978 Ixion
28978 Ixion is a Kuiper belt object discovered on May 22, 2001. Ixion is a plutino and a very likely dwarf planet; its diameter of 650 km estimated by Spitzer makes it about the fifth largest plutino. It is named after Ixion, a figure from Greek mythology...

. The name becomes official after its publication in the Minor Planet Circular
Minor Planet Circular
The Minor Planet Circulars is a scientific journal that is generally published on the date of each full moon by the Minor Planet Center. The Circulars contain astrometric observations, orbits and ephemerides of minor planets, comets and certain natural satellites...

 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, then the right to name it is given also to identifiers of the various apparitions of 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 CSBN 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
Linear
In mathematics, a linear map or function f is a function which satisfies the following two properties:* Additivity : f = f + f...

 or LONEOS have discovered so many thousands of new asteroids that the Center for Small Body Nomenclature 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 Annefrank (5535 Annefrank
5535 Annefrank
5535 Annefrank is an inner main-belt asteroid, and member of the Augusta family. It was discovered by Karl Reinmuth in 1942. It is named after Anne Frank, the Dutch-Jewish diarist who died in a concentration camp...

)), although exceptions are possible (such as James Bond (9007 James Bond
9007 James Bond
Asteroid 9007 James Bond was discovered on 5 October 1983 by Antonín Mrkos at the Kleť Observatory in the Czech Republic.It is named in honour of the British novelist Ian Fleming who wrote a series of twelve novels and nine short stories about the fictional British spy James Bond between 1953 and...

)), and since 1982 limited to a maximum length of sixteen characters, including spaces and hyphens. Letters with diacritic
Diacritic
A diacritic is a glyph added to a letter, or basic glyph. The term derives from the Greek διακριτικός . Diacritic is both an adjective and a noun, whereas diacritical is only an adjective. Some diacritical marks, such as the acute and grave are often called accents...

s are accepted, although the diacritical marks are usually omitted in everyday usage. 4090 Říšehvězd
4090 Ríšehvezd
4090 Říšehvězd is a main-belt asteroid with an orbital period of 1321.9792938 days . The asteroid was discovered on September 2, 1986.-References:...

 is an asteroid with the most diacritics (four). Military and political leaders are unsuitable until they are dead for 100 years. Nowadays, names of pet animals are discouraged, but there are some from the past. Names after people, companies or products known only for success in business are not accepted, as well as citations that resemble advertising.

Whimsical names can be used for relatively ordinary asteroids (such as 26858 Misterrogers
26858 Misterrogers
26858 Misterrogers is a main-belt asteroid named after children's television host Fred Rogers. Rogers, who had a lifelong fascination with the sky and astronomy —he obtained a pilot's license while still in high school— also produced a planetarium show called The Sky above Mister...

), but those belonging to certain dynamical groups are expected to follow more strictly defined naming schemes.
  • Trojan asteroids (those that librate
    Libration
    In astronomy, libration is an oscillating motion of orbiting bodies relative to each other, notably including the motion of the Moon relative to Earth, or of Trojan asteroids relative to planets.-Lunar libration:...

     in 1:1 resonance
    Orbital resonance
    In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...

     with Jupiter) are named for heroes of the Trojan War
    Trojan War
    In Greek mythology, the Trojan War was waged against the city of Troy by the Achaeans after Paris of Troy took Helen from her husband Menelaus, the king of Sparta. The war is among the most important events in Greek mythology and was narrated in many works of Greek literature, including the Iliad...

    . Asteroids at Lagrangian point
    Lagrangian point
    The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects...

      are named after Greek warriors (such as 588 Achilles
    588 Achilles
    588 Achilles is an asteroid discovered on February 22, 1906, by the German astronomer Max Wolf. It was the first of the trojan asteroids to be discovered, and is named after Achilles, the fictional hero from the Iliad. It orbits in the Lagrangian point of the Sun-Jupiter system...

    ) and asteroids at after Trojans (such as 884 Priamus
    884 Priamus
    884 Priamus is a Trojan asteroid that orbits the Sun at the same distance as the planet Jupiter. It is located in the trailing Lagrangian point.It was discovered by Max Wolf on September 22 1917 in Heidelberg, Germany.-External links:*...

    ).
  • Trans-Jovian minor planets crossing or approaching the orbit of a giant planet
    Gas giant
    A gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in the Solar System: Jupiter, Saturn, Uranus, and Neptune...

     but not in a stabilizing resonance are named for centaur
    Centaur
    In Greek mythology, a centaur or hippocentaur is a member of a composite race of creatures, part human and part horse...

    s (such as 2060 Chiron
    2060 Chiron
    2060 Chiron is a minor planet in the outer Solar System. Discovered in 1977 by Charles T. Kowal , it was the first-known member of a new class of objects now known as centaurs, with an orbit between Saturn and Uranus.Although it was initially classified as an asteroid, it was later found to...

    ).
  • Objects in Neptune's 3:2 mean-motion-reference resonance are given mythological names associated with the underworld
    Underworld
    The Underworld is a region which is thought to be under the surface of the earth in some religions and in mythologies. It could be a place where the souls of the recently departed go, and in some traditions it is identified with Hell or the realm of death...

     (such as 90482 Orcus
    90482 Orcus
    90482 Orcus is a trans-Neptunian object in the Kuiper belt with a large moon. It was discovered on February 17, 2004 by Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale University. Precovery images as early as November 8, 1951 were later identified...

    ).
  • Classical Kuiper belt objects are given mythological names associated with creation (such as 50000 Quaoar
    50000 Quaoar
    50000 Quaoar is a rocky trans-Neptunian object in the Kuiper belt with one known moon. Discovered on June 4, 2002 by astronomers Chad Trujillo and Michael Brown at the California Institute of Technology from images acquired at the Samuel Oschin Telescope at Palomar Observatory, it is thought by...

    ).
  • Objects that approach or cross Earth's orbit are still given mythological names (such as 1862 Apollo
    1862 Apollo
    1862 Apollo is a Q-type asteroid, discovered by Karl Reinmuth in 1932, but lost and not recovered until 1973. It is named after the Greek god Apollo....

    ), preferably male.

Comets

The names given to comets have followed several different conventions over 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
Edmond Halley
Edmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of the eponymous Halley's Comet. He was the second Astronomer Royal in Britain, following in the footsteps of John Flamsteed.-Biography and career:Halley...

, who had calculated its orbit. Similarly, the second known periodic comet, Comet Encke
Comet Encke
Comet Encke or Encke's Comet is a periodic comet that completes an orbit of the Sun once every three years — the shortest period of any known comet...

 (formally designated 2P/Encke), was named after the astronomer, Johann Franz Encke, who had calculated its orbit rather than the original discoverer of the comet, Pierre Méchain. Other comets that bore the possessive include "Biela's Comet" (3D/Biela
3D/Biela
Biela's Comet or Comet Biela was a periodic comet first recorded in 1772 by Montaigne and Messier and finally identified as periodic in 1826 by Wilhelm von Biela. It was subsequently observed to split in two and has not been seen since 1852...

) and "Miss Herschel's Comet" (35P/Herschel-Rigollet
35P/Herschel-Rigollet
35P/Herschel–Rigollet is a periodic comet discovered by Caroline Herschel on 1788-12-21.-1789 apparition:Caroline Herschel first observed the comet on 21 December 1788 and it was observed later that night by her brother William Herschel who described it as looking like a bright nebula and about...

, 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 is named after up to its first three independent discoverers. 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 the instrument (for example, Comet IRAS-Araki-Alcock
Comet IRAS-Araki-Alcock
Comet IRAS–Araki–Alcock is a small comet that, in 1983, made the closest approach to the earth of any comet in 200 years; only Lexell's Comet, in 1770, and 55P/Tempel-Tuttle, in 1366, are thought to have come closer.The comet was named after its discoverers – the Infrared Astronomical Satellite and...

 (C/1983 H1) was discovered independently by the IRAS
IRAS
The Infrared Astronomical Satellite was the first-ever space-based observatory to perform a survey of the entire sky at infrared wavelengths....

 satellite and amateur astronomers Genichi Araki and George Alcock
George Alcock
George Eric Deacon Alcock was an English astronomer. He was one of the most successful visual discoverers of novae and comets....

). Comet 105P/Singer Brewster
105P/Singer Brewster
105P/Singer Brewster is a periodic comet in our solar system. Its name is unusual: co-discovered comets commonly bear the names of the co-discoverers linked by hyphens rather than dashes...

, discovered by Stephen Singer-Brewster
Stephen Singer-Brewster
Stephen C. Singer-Brewster is an American astronomer.Mr. Brewster is a member of the American Association of Variable Star Observers. He participated in the Palomar Planet Crossing Asteroid Survey as an observer and astrometrist under the direction of Dr. Eleanor F. Helin from 1985 to 1988....

, should by rights have been named "105P/Singer-Brewster", but this would have led most readers to believe it had been a joint discovery by two astronomers named Singer and Brewster, respectively, so the hyphen was replaced by a space. Other comets with spaces in their names, however, reflect their discoverers' name spellings (e.g. 32P/Comas Solá
32P/Comas Solá
32P/Comas Solà is the name of a periodic comet with a current orbital period of 8.8 years.The comet nucleus is estimated to be 8.4 kilometers in diameter.-Discovery:...

).

Until 1994, the systematic naming of comets (the "Old Style") involved first giving them a provisional designation of the year of their discovery followed by a lower case letter indicating its order of discovery in that year (e.g. the first Comet Bennett
Comet Bennett
Comet Bennett, formally known as C/1969 Y1 , was one of two brilliant comets to grace the 1970s, along with Comet West...

 is 1969i, the 9th comet discovered in 1969). In 1987, more than 26 comets were discovered, so the alphabet was used again with a "1" subscript, very much like what is still done with asteroids (an example is Comet Skorichenko-George
Comet Skorichenko-George
Comet Skorichenko–George is also designated C/1989 Y1, 1990 VI, and 1989e1. It was discovered on December 17, 1989 by Doug George of Kanata , Ontario, Canada, and Soviet astronomer Boris Skoritchenko...

, 1989e1). The record year was 1989, which went as high as 1989h1. Once an orbit had been established, the comet was given a permanent designation in order of time of perihelion passage, consisting of the year followed by a Roman numeral. For example, Comet Bennett (1969i) became 1970 II.

Increasing numbers of comet discoveries made this procedure difficult to operate, and in 1994 the International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

 approved a new naming system (the "New Style"). Comets are now designated by the year of their discovery followed by a letter indicating the half-month of the discovery (A denotes the first half of January, B denotes the second Half of January, C denotes the first half of February, D denotes the second half of February, etcetera) and a number indicating the order of discovery. To exemplify, the fourth comet discovered in the second half of February 2006 would be designated 2006 D4. "I" and "Z" are not used when describing the half of a particular month the comet was discovered. Prefixes are also added to indicate the nature of the comet, with P/ indicating a periodic comet, C/ indicating a non-periodic comet, X/ indicating a comet for which no reliable orbit could be calculated (typically comets described in historical chronicles), D/ indicating a comet which has broken up or been lost, and A/ indicating an object at first thought to be a comet but later reclassified as an asteroid. Periodic comets also have a number indicating the order of their discovery. Thus Bennett's comet has the systematic designation C/1969 Y1. Halley's Comet, the first comet to be identified as periodic, has the systematic name 1P/1682 Q1. Comet Hale-Bopp
Comet Hale-Bopp
Comet Hale–Bopp was perhaps the most widely observed comet of the 20th century, and one of the brightest seen for many decades...

's systematic name is C/1995 O1. The famous Comet Shoemaker-Levy 9
Comet Shoemaker-Levy 9
Comet Shoemaker–Levy 9 was a comet that broke apart and collided with Jupiter in July 1994, providing the first direct observation of an extraterrestrial collision of solar system objects. This generated a large amount of coverage in the popular media, and the comet was closely observed by...

 was the ninth periodic comet jointly discovered by Carolyn Shoemaker, Eugene Shoemaker, and David Levy (the Shoemaker-Levy team has also discovered four non-periodic comets interspersed with the periodic ones), but its systematic name is D/1993 F2 (it was discovered in 1993 and the prefix "D/" is applied, since it was observed to crash into Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

).

Some comets were first spotted as minor planets, and received a temporary designation accordingly before cometary activity was later discovered. This is the reason for such comets as (Catalina 2) or (Spacewatch-LINEAR). The MPECs and html version of IAUCs, because of their telegraphic style, "flatten out" the subscripts, but PDF version of IAUCs and some other sources such as the Yamamoto Circulars and the Kometnyj Tsirkular use them.

Designations for extra-solar planets

At the moment, according to the IAU, there is no agreed system for designating planets orbiting around other stars, nor is there any plan to create a naming system for extra-solar planets http://www.iau.org/PLANETS_AROUND_OTHER_STARS.247.0.html. A trend that is gaining prominence uses a lower-case letter (starting with "b") to extend the star's designation. For example, 16 Cygni Bb
16 Cygni Bb
16 Cygni Bb or 16 Cyg Bb is an extrasolar planet approximately 70 light-years away in the constellation of Cygnus. The planet was discovered orbiting the sun-like star 16 Cygni B, one of two solar-mass components of the triple star system 16 Cygni...

 is the first extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...

 found around the star 16 Cygni B, itself a member of the triple star system 16 Cygni
16 Cygni
16 Cygni or 16 Cyg is a triple star system approximately 70 light-years away from Earth in the constellation of Cygnus. It consists of two Sun-like yellow dwarf stars, 16 Cygni A and 16 Cygni B, together with a red dwarf, 16 Cygni C...

. Occasionally planet names appear by appending the star name with roman numerals http://www.nineplanets.org/earth.html (e.g. Sol I, Sol II, Sol III), but this is not used much outside of science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

 or roleplay http://johnsonm.com/garden_universe/Worlds/Worlds1/Sol/Venus.htmhttp://www.orionsarm.com/worlds/Earth.html.

See also

  • Planetary nomenclature
    Planetary nomenclature
    Planetary nomenclature, like terrestrial nomenclature, is a system of uniquely identifying features on the surface of a planet or natural satellite so that the features can be easily located, described, and discussed. The task of assigning official names to features is taken up by the International...

  • List of astronomical objects named after people
  • List of basic astronomy topics
  • List of brightest stars
  • List of minor planets (asteroids)
  • Naming of moons
  • Provisional designation in astronomy
    Provisional designation in astronomy
    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 calculated...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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