There are no more than a few thousand stars that appear sufficiently bright in Earth's sky to be visible to the naked eye.
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.
[1] The IAU is the only internationally recognized authority for assigning astronomical designations to celestial objects and surface features on them.
Different star catalogues then have different naming conventions for what goes after the initialism, but modern catalogs tend to follow a set of generic rules for the data formats used.
[8] The star nearest to Earth 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).
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.
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, the Southern Cross, Epsilon Carinae (ε Car) in Carina, Lambda Scorpii (λ Sco) in Scorpius and Sigma Sagittarii (σ Sgr) in Sagittarius.
Most modern catalogues are generated by computers, using high-resolution, high-sensitivity telescopes, and as a result describe very large numbers of objects.
A large number of black holes are designated by their position in the sky and prefixed with the instrument or survey that discovered them.
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 is formed by the standard prefix "SN", the year of discovery, and a suffix composed of one to three letters of the Latin alphabet.
Subsequent supernovae of that year are designated with pairs of lower-case letters from "aa" to "az", and then continuing with "ba" until "zz".
Driven by advances in technology and increases in observation time in the early 21st century, hundreds of supernovae were reported every year to the IAU, with more than 500 catalogued in 2007.
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.
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).
French astronomers began calling it Herschel before German Johann Bode proposed the name Uranus, after the Greek god.
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.
The scientific nomenclature for 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.
[20] The lowercase lettering style is drawn from the IAU's long-established rules for naming binary and multiple star systems.
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 the wider concept from any specific example.
Satellites of Uranus are instead named after characters from works by William Shakespeare or Alexander Pope, such as Umbriel or Titania.
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.
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 the Medici family failed to win currency.
Later, "The System of Lunar Craters, quadrants I, II, III, IV" was published, under the direction of Gerard P. Kuiper.
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.
Currently, 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 the IAU President and General Secretary.
When enough observations of the same object are obtained to calculate a reliable orbit, a sequential number is assigned by the Minor Planet Center to the minor-planet designation.
[23] 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.
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.