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Astronomical naming conventions

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The International Astronomical Union (IAU) is the body recognized by astronomers worldwide as the naming authority for astronomical bodies. It has created a number of systematic naming systems for bodies of various sorts.

Names of stars

According to the IAU, apart from a limited number of bright stars with historic names, stars do not have names. Instead, they have designations assigned to them by a variety of different star catalogues.

Older catalogs either assigned a number to each object, or used a systematic naming scheme such as combining constellation names with Greek letters.

Most modern catalogues contain large numbers of objects, 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 SDSSp indicates "Sloan Digital Sky Survey preliminary objects", and the other characters indicate celestial coordinates.

Multiple sky catalogues mean that some stars have more than one designation. For example, the star with the Arabic name of Rigil Kentaurus, also has the Bayer designation of Alpha Centauri.

For a more detailed treatment of the designations of stars, see star designation.

Managing the acronyms of star catalogues

The IAU is the ultimate maintainer of the namespace 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 "acronym", which is kept globally unique by the IAU. Different star catalogues then have different naming conventions for what goes after the acronym, but modern catalogues tend to follow a set of generic rules for the data formats used.

Names of galaxies

Like stars, most galaxies do not have names. Until relatively recent times, it was not known what galaxies were, and they were classified simply as "nebular objects". Som of them were named after the constellations in which they appeared, and were given names like "Andromeda nebula". The creation of the Messier catalog gave numbers to many of the brightest nebulae; these Messier numbers of well known objects are often used as names. For example, the galaxy formerly known as the "Andromeda nebula", now called the Andromeda galaxy, is often just referred to as M31.

Since galaxies are even more numerous than individual stars that can be discriminated, astronomers have given up giving them names. Most are just given designations in the same way as stars.

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; Mercry, Venus, Mars, Jupiter and Saturn. Our own planet is named the Earth.

Three more planets were discovered later:

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, when Sir William Herschel discovered Uranus in 1781, and originally called it Georgium Sidus (George's Star) in honour of King George III of England. 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.

Since the discovery of Pluto, a large number of large planetoids have been discovered. Under modern criteria, it is dubious whether Pluto would have been called a planet.

Provisional designations for minor planets

Minor planets (also known as planetoids) such as asteroids and comets are initally assigned provisional designations when first discovered. This is done by using coding the date of discovery by the four-digit year number (according to the Common Era), and then a set of letters for the time period within the year, and finally a sequence number to make the designation unambiguous if multiple discoveries are made in a short period of time.

These provisional designations can later be replaced by permanent designations if appropriate.


Asteroid designations

Asteroids have names of the form 433 Eros and 951 Gaspra: they consist of a sequence number (starting at 1 for 1 Ceres, discovered in 1801), and a mnemonic name. The discoverer of the asteroid is usually allowed to choose the name.

Other planetoids

Other planetoids are named similarly to asteroids; the object with provisional designation 2002 LM60 now has an official minor planet number, and a name, assigning it the minor planet name 50000 Quaoar, or simply Quaoar. 2003 VB12 is likely to be named "Sedna". IAU rules specify themes for naming planetoids: for example, all planetoids in Pluto-like orbits are to be named after creation deities.

Designations for comets

to be written

Nomenclature of features on planets and satellites

The IAU has been the arbiter of planetary and satellite nomenclature since its organizational meeting in 1919 in Brussels. At that time a committee was appointed to regularize the chaotic lunar and Martian nomenclatures then current. The IAU committee was an outgrowth of an earlier committee established in 1907 by the Council of the International Association of Academies, meeting in General Assembly in Vienna. This committee had been charged with the task of clarifying the lunar nomenclature but had not published a report, due to a succession of deaths of members. However, a great deal of preliminary work had been done by Mary Adela Blagg, a volunteer who had been assisting a deceased member of the Council of International Association of Academies, Samuel Arthur Saunder, before the IAU was ever formed. Blagg was appointed as a member of the first IAU commission on lunar nomenclature.

The IAU appointed Miss Blagg and several other astronomers to the newly commissioned nomenclature committee, chaired by H. H. Turner. The report of this committee, "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 catalogues listed the names (or other designations) and coordinates of features in the current, greatly expanded lunar nomenclature; the accompanying maps showed their locations. These works were adopted by the IAU and became the recognized sources for lunar nomenclature.

The Martian nomenclature was clarified in 1958, when acommittee of the IAU chaired by Audouin Dollfus 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 G. V. Schiaparelli (1879) and expanded in the early 20th century by E. M. Antoniadi (1929), an Greek-born astronomer working at Meudon, France.

The requirements for extraterrestrial nomenclature were dramatically changed in 1957 when the age of space exploration was inaugurated by the successful flight of Sputnik and by America's consequent determination to land a man on the Moon in the 1960s. As detailed images became available of one newly discriminated extraterrestrial surface after another, the need to name features on these surfaces became evident. Once again the IAU assumed the task.

In 1970, in response to the successful Mariner flyby missions to Mars during the 1960's, and in anticipation of the Mariner 9 Mars Orbiter, a Mars nomenclature working group was formed, chaired by Gerard de Vaucouleurs; this group was asked to designate names for the topographic features shown in the new spacecraft images. At about the same time, Donald H. Menzel chaired an ad hoc lunar committee that suggested names for features discriminated by the Soviet Zond and American Lunar Orbiter and Apollo cameras.

In 1973, the nomenclature groups were reorganized and expanded. The Working Group for Planetary System Nomenclature (WGPSN) was appointed with Peter Millman of Canada as its first president. Task groups for the Moon, Mercury, Venus, Mars, and the Outer Solar System were formed to conduct the preliminary work of choosing themes and proposing names for features on each newly discriminated planet and satellite. A new task group was formed in 1984 to name surface features on small primitive bodies (asteroids and comets).

Designations for planets around other stars

to be written


See also:

Some contents adapted from the public domain document at http://planetarynames.wr.usgs.gov/history.html Please update as necessary.

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