While astronomers have adopted a policy of not naming stars – as there is no point in trying to change traditional names which have been in use for centuries – they do give names to just about everything else in the sky. An extensive set of conventions and rules have been established, for the naming of various types of objects and planetary features. In particular, there are several classes of objects which are named in honour of people – but these nearly always commemorate people who have contributed significantly to science, or to other aspects of human culture. In this section, I’ll briefly explain what these classes of objects are, and how they are named.
3.1. The International Astronomical Union
The International Astronomical Union ( IAU ) is the world’s overall “governing body” for astronomy; it was founded in 1919, and has its headquarters in Paris. Its members are professional astronomers, qualified to Ph.D. level or higher, from many countries; its function is to coordinate, through international agreement, all aspects of astronomy research and education.
One of the IAU’s many tasks has been to establish conventions and standards for use in the science of astronomy, to prevent confusion and ambiguities. For example, in 1933, it “standardised” the names and boundaries of the constellations. Before that time, there was nothing “official” about constellations; they were simply arbitrarily defined patterns of stars, some resulting from thousands of years of tradition, and others being more recent inventions. Many of the latter kind had been adopted and later abandoned, and some variations were in use. There were no strictly defined “boundaries” between constellations, so there was room for ambiguity, when it came to specifying the constellation in which a particular star or other object was located.
The IAU adopted a standard list of 88 constellations, and defined their boundaries in terms of lines of right ascension and declination, so that there is no longer any ambiguity in saying that an object is located in a particular constellation. ( Of course, the constellations have no scientific significance whatsoever; they are simply used as a means of dividing up the sky into manageable regions, for the purpose of describing the locations of objects. )
Another task of the IAU has been to establish conventions for the naming of objects within the Solar System – such as planetary satellites, asteroids and comets – and the surface features on the Moon, planets and other bodies. These naming conventions are what concern us here.
3.2. Lunar and planetary features
It’s hardly surprising that when astronomers first began to use telescopes in the 17th Century, one of the first things they did was to draw maps of the Moon. Many people devised their own systems of nomenclature for its surface features, but the system which came into general use was that of Father Giovanni Riccioli, who published his map in 1651. Riccioli adopted three different naming conventions, for the Moon’s mountain ranges, its flat plains or “maria” and its craters. For the craters, he used human names; he named them in honour of famous scientists – mainly astronomers – of his own and earlier times.
Later astronomers continued the tradition, and named craters after scientists of later generations – expanding the system to include scientists of all disciplines, and not only astronomers – so that the Moon has become a “roll of honour” for scientists and philosophers. The IAU officially adopted the lunar names which had been assigned before its formation, and established a set of rules for the allocation of new names.
During the Space Age, as spacecraft began to reveal to us the surfaces of the planets and their satellites, the IAU established an extensive set of conventions and rules for the naming of their features, whereby each Solar System body has its features named in accordance with a specific set of rules. The tradition of naming craters after people has been continued for craters on Mercury, Mars and Venus, using a particular category of names for each planet.
On Mars, as on the Moon, craters are named in honour of astronomers and other scientists – but specifically, those who have contributed to the study of Mars. But a different approach was adopted for Mercury and Venus.
In Greek and Roman mythology, the god Mercury, as well as being the messenger of the gods, was also said to be a great musician. Therefore, the craters on Mercury have been named in honour of people who have contributed to music and the arts – famous composers, artists, poets and writers. So while the Moon is a roll of honour for scientists, Mercury is an equivalent one for culture and the arts.
Since Venus is the only planet named after a goddess, all its surface features ( with the exception of three, which were named before the convention was established ) are given female names. Some of its features are named after female deities and mythical heroines from a variety of cultures and mythologies; its craters, however, are named in honour of real women – famous ones from history, and those who contributed significantly to science, the arts or any other aspect of human culture.
Naming lunar and planetary features is the responsibility of an IAU committee called the Working Group for Planetary System Nomenclature ( WGPSN ); anyone may propose names, but the WGPSN decides which ones are accepted as official names. Within the conventions described above, it has a number of rules regarding the acceptability of names. Firstly, no individual can be honoured with a crater during their lifetime; no-one can be considered until at least three years after their death. Secondly, the policy is to honour people from as many different countries as possible, to avoid any nationalistic bias.
Certain categories of names are specifically forbidden, to avoid controversy; these include such potentially contentious classes as political, military or religious leaders. Some proposed names are even rejected for purely linguistic reasons; unfortunately, it sometimes transpires that someone’s name happens to sound like a rude or offensive word in some other language!
3.3. Asteroids
There are now tens of thousands of known asteroids, or minor planets. Each one discovered is initially given a designation such as 2003VB12, which identifies its date and order of discovery. After its orbit has been accurately determined, it is given a unique number, and later also given a name. Several thousand of them have so far been named; each of these is identified by both its number and name, such as (1) Ceres or (1566) Icarus.
The first asteroid was discovered in 1801; several hundred were discovered during the 19th Century, long before the IAU was formed. A tradition was established, whereby the discoverer of an asteroid had the right to name it. Today, the discoverer still has the privilege to propose a name, subject to it being approved by the IAU. Naming asteroids is the responsibility of another IAU committee, the Working Group for Small Bodies Nomenclature ( WGSBN ).
The first couple of hundred asteroids were given names from Greek and Roman mythology, following the tradition used for the names of the planets and their satellites. But after the supply of these names ran out, discoverers began assigning all kinds of names. In pre-IAU days, there were no particular rules, so the names of the first thousand or so asteroids form a bewildering hodgepodge. Some were named after their discoverers’ home countries or cities, some after universities, and some even after plants and flowers. And many discoverers – somewhat ironically, given the subject of this essay – did name asteroids after their wives, children, dear departed grannies, etc. There is even one asteroid which was named by auction; its discoverer was hard up, and sold his right of naming to the highest bidder! ( This is why the IAU now gives a discoverer the privilege of naming, rather than the right, as the latter could be sold or passed on to a next of kin. )
Today, of course, the IAU takes a much more systematic approach. The practice of naming asteroids after wives, children, etc. is now forbidden; the vast majority of new ones are still named after people, but usually people who have contributed to astronomy. Each proposal submitted to the WGSBN has to be accompanied by a citation to justify it.
Though the discoverer still has the first option of proposing a name, the vast majority of asteroid discoveries in recent years have been made by automated search programmes, which discover them by the hundred or thousand. The people who run the searches simply hand over their privilege of naming to the IAU; every so often, the WGSBN assigns a batch of names to asteroids which previously had only numbers. Anyone may propose names to the committee, which if approved, will be allocated in this way at some time in the future.
The rule about having to be dead doesn’t apply here; many people have been honoured with an asteroid during their lifetime. While most are named after astronomers, there are still some exceptions; some are named after people from the arts and entertainment – e.g. one for each of the Beatles – and some honour the astronauts and cosmonauts who have died during space missions.
[ Update, May 2021: I’m now responsible myself for naming an asteroid! Jack Youdale ( 1932-2017 ) was an eminent and highly respected British amateur astronomer, telescope maker and advocate of public outreach, and was a friend of mine for over 30 years. A citation which I sent to the WGSBN has been accepted, and an asteroid is now named in his honour - (11443) Youdale. ]
3.4. Comets
The naming system for comets is very simple; each one is named in honour of its discoverer – or if two or more people discover one independently, it’s named after the first two. ( It used to be permissible to use three names, but this led to some very unwieldy names - such as Comet Sugano-Saigusa-Fujikawa! – so the limit was reduced to two. ) But since some people have discovered several comets each, there are many instances of several comets bearing the same name; therefore, it’s also necessary to give each one a unique identifier. In the modern convention, this consists of the prefix “C/”, followed by the year of discovery, and a unique letter and number which identify the order of discovery within that year. For example, Comet Hale-Bopp, which became so spectacular in 1997, was discovered two years earlier, independently by Alan Hale and Thomas Bopp; its official designation is C/1995 O1 Hale-Bopp.
There are a few historical exceptions. The most famous comet of all, Comet Halley, was certainly not discovered by Edmond Halley; it had been observed at many previous apparitions, going back as far as 240 BC. But Halley was the first person to realise that comets are in orbit around the Sun, and therefore return periodically. When he observed the comet which now bears his name, at its apparition of 1682, he realised that it was the same comet which had previously been seen in 1531 and 1607, and predicted that it would return in 1758-59. Of course, he didn’t live to see himself proved right – but it’s only fitting that the comet was named in his honour.
There are several other short-period comets, which have been seen at many apparitions, and are named after the people who first computed their orbits.