The universe is full of mysteries, and among the most captivating is the way humanity has chosen to name the worlds it has been discovering beyond our solar system with patience and technology. Today, exoplanets—planets orbiting stars other than the Sun—are part of the everyday language of astronomy, but few know the stories, rules, and curiosities behind their baptism.
In this article, we'll delve deeply into the origins of exoplanet names, from the earliest mythological traditions to the meticulous standards established by the International Astronomical Union, including anecdotes, debates, and the occasional unexpected twist that accompanies the fascinating task of naming new worlds.
The wonder of the cosmos and the obsession with naming
Since ancient times, humans have felt an irresistible attraction to the firmament and have wanted to name every light that crosses the night. The custom of naming celestial bodies dates back to civilizations such as the Babylonians, Egyptians, Greeks, and Romans. Each culture saw the stars as divine representations, legendary figures, or symbols of some aspect of human existence. However, the craze for naming reached a new level as our capacity for space exploration advanced.
The term "planet" comes from the Greek word 'planētēs', which means 'wanderer' or 'vagabond', and was used to designate those lights in the firmament that changed position in relation to the fixed stars. The oldest ones, visible to the naked eye, were named after deities or important figures in Greco-Roman mythology and other cultures.
A brief history of the nomenclature of the planets in the solar system
For millennia, the planets of the solar system were identified and renamed according to the knowledge and beliefs of each civilization. The Romans consolidated the use of names from their pantheon for the five planets visible to the naked eye:
- Mercury: the swift messenger of the gods, for his rapid movement in the sky.
- Venus: the goddess of love and beauty, reflected in the intense brightness of the planet.
- Mars: the god of war, chosen for the reddish color of the planet, which evokes the blood of battle.
- Jupiter: the king of the gods, in honor of the largest planet.
- Saturn: the god of time and agriculture, father of Jupiter, assigned to the planet with visible rings since ancient times.
The Earth, our planet, never had a name derived from Greco-Roman mythology, and its name comes from ancient Germanic and various languages. The Greeks called her Gea and the Romans Gaia.
The arrival of the telescope and the advances in space exploration unleashed a new wave of astronomical baptisms. Uranus, discovered in 1781, was initially named "George's Star" in honor of King George III of England, but mythological tradition eventually prevailed, and Uranus, the father of Saturn, was chosen. Neptune and Pluto followed suit, named after the god of the sea and the lord of the underworld, respectively. Interestingly, the name Pluto was suggested by an 11-year-old girl who was a fan of Greco-Roman mythology.
The Moons and Other Bodies: Myths, Literature, and Creativity
The universe is populated not only by planets, but also by moons, asteroids, and comets, all with names that tell surprising stories. The moons of Mars, Phobos and Deimos, are named for the fears and terrors that accompanied the god of war. Jupiter has moons named Europa, Io, Callisto, and Ganymede, all of them lovers or characters linked to Zeus in Greek tales, while Saturn and Uranus have been given names inspired not only by mythology but also by literary figures, such as those from the universe of Shakespeare or Alexander Pope, a notable exception to the rigid mythological tradition.
Thus, mythology, creativity, and science have gone hand in hand in naming the objects that make up our cosmic neighborhood.
The leap to other systems: The origin of exoplanet names
For centuries, the existence of planets around other stars was the subject of philosophical and scientific speculation, but we lacked direct evidence. The 20th century, and especially the beginning of the 21st, have been a true revolution: thousands of exoplanets have been discovered thanks to the development of telescopes and highly precise detection methods such as transit, radial velocity, and gravitational lensing.
A new challenge arises here: how do we organize and name these new worlds? Giving them spontaneous names would be unfeasible and a source of confusion, so the international astronomical community, led by the International Astronomical Union (IAU), established a meticulous and orderly system.
How does the official nomenclature of exoplanets work?
The official system for naming exoplanets has its roots in binary star nomenclature. Essentially, each planet is named after its host star, followed by a lowercase letter starting with 'b'. The letter 'a' is reserved for the parent star, so the first planet discovered in the system is named, for example, '51 Pegasi b'. If more planets are discovered, they are assigned subsequent letters in order of discovery: 51 Pegasi c, 51 Pegasi d, and so on.
If the planetary system belongs to a binary or multiple star, capital letters are used for stars and lowercase letters for planets, for example, 16 Cygni Bb. However, in systems where the secondary star is of little importance or was discovered after the planet, the capital letter may be omitted.
This nomenclature, although logical for scientists, often seems cold and impersonal to the non-specialist public. It is not difficult to imagine the confusion when faced with names like 'HR 8799 c' or 'PSR 1257 12 d', so far from the evocative appeal of mythological names.
The involvement of the International Astronomical Union: from science to collective sentiment
The IAU, the leading international body for regulating astronomical nomenclature, has strived to strike a balance between scientific precision and the human need to give meaning to celestial bodies. For this reason, for decades, the UAI was reluctant to accept "commercial," personal, or excessively subjective names.
However, in response to growing demand and public interest, in recent years the IAU has been opening the door to public participation in the naming of exoplanets and their stars. One example is the "NameExoWorlds" initiative, which allows associations, clubs, and planetariums to propose names for a selected list of exoplanets and star systems. After rigorous screening, the general public can vote on the final proposals.
The rules and criteria for naming exoplanets
Although participation is encouraged, there are strict rules to avoid problems or duplication. Some of the guidelines established by the UAI are:
- The name must be 16 characters or less and preferably be a single word.
- They should be able to be pronounced well in any language and should not be offensive.
- They cannot coincide with or resemble names already assigned to other celestial bodies.
- Names of living people, pets, political or religious figures, and trademarks are excluded.
- Each planetary system must maintain a semantic unity, that is, the names of planets and stars must be thematically related to each other (mythology, literature, history, etc.).
Furthermore, all nominations go through two approval filters by scientific committees before being submitted to the general vote. This way, jokes, controversies, or names lacking universal meaning are avoided.
Curiosities and anecdotes about the naming of exoplanets
Throughout the history of exoplanet discovery, notable episodes have emerged with personalities and names that have become part of the history of astronomy. Among the most curious cases are:
- The "Tannhäuser Gate" and popular culture: Although fictional, the famous quote from the film Blade Runner illustrates the public's fascination with naming imaginary worlds and the difference with rigid official nomenclature. The IAU typically rejects names inspired by trademarks, films, or living people, although it recognizes the importance of fiction in keeping interest in space exploration alive.
- The role of fans and associations: The involvement of planetariums, astronomy clubs, and schools has led to some exoplanets being named after educational groups or popularizers, reinforcing the participatory dimension of modern astronomy.
- The thematic unity of each system: One of the most striking requirements is that all the bodies in a planetary system must be related to each other. Thus, it is not unusual to find systems whose exoplanets and stars have been named after figures from the same legend, region, or era.
Major discoveries and evolution of exoplanet exploration
The history of exoplanet discovery is filled with fundamental milestones and genuine scientific careers. From the first false alarms in the 1257th and 12th centuries, through the confirmation of the pulsar PSR B1992+51 in XNUMX and the discovery of XNUMX Pegasi b, astronomy has undergone a true revolution.
Detection techniques have evolved and now allow us not only to determine how many planets exist, but also to estimate their masses, radii, compositions, and even the possible presence of atmospheres compatible with life. This explosion of information has made it necessary to perfect cataloging and naming systems, as the volume of data continues to grow.
Rules, exceptions and debates in astronomical nomenclature
Although the UAI establishes clear rules, there is no shortage of debates and exceptions. The cases of planets like KOI-4878.01, which are extremely similar to Earth, or systems with planets named "out of order" due to their time of discovery, underscore the difficulty of maintaining consistency in a science that is constantly evolving.
Sometimes the designation of a planet does not correspond to the order from the main star, but simply to the chronological order in which it was found. This can lead to unintuitive nomenclature tables, but they are necessary to maintain traceability of the findings.
The influence of nomenclature on the social and cultural perception of astronomy
Naming exoplanets is not only a technical issue, but also a symbolic one. From a cultural perspective, having a planet named after a hero, legend, writer, or universal figure brings the universe closer to people, humanizes it, and makes it part of their heritage.
Each name added to the catalog is an opportunity to connect generations, educate young people, and keep alive the stories that have accompanied humanity in its search for meaning in the cosmos.
Projects, missions, and the future of exoplanet baptism
Today, the list of named exoplanets is constantly growing thanks to the work of cutting-edge instruments and projects such as HARPS, TESS, Kepler, COROT, and automated survey campaigns. This means that the catalogs include everything from gas giant planets to super-Earths, ocean worlds, and bodies that defy traditional classification.
In this context, the trend is to expand the list of approved names and allow society to remain involved in this process, thus strengthening the link between science and the collective imagination.
List of some key methods, missions, and astronomers involved in the search for and naming of exoplanets
- HARPS: High-Precision Radial Velocity Planet Finder, vital in the detection of low-mass planets.
- Kepler, COROT, TESS: Space missions dedicated to the systematic exploration of exoplanets through transits.
- ESPRESSO, OGLE, SuperWASP, MEarth, TRAPPIST, SPECULOOS: Specialized instruments, networks, and telescopes have exponentially increased the pace of discoveries in the last decade.
- Prominent Astronomers: Michel Mayor, Didier Queloz, Geoffrey Marcy, Michel Udry, among others, pioneers in the identification and study of exoplanets.
Planet classification and subtypes: Does this affect the name?
The scientific classification of exoplanets (by mass, size, temperature, or composition) does not determine their name, but it does enrich the discourse about their nature. Thus, we speak of Earths, super-Earths, Neptunian planets, gas giants, or lava planets, and even exoplanets of exotic composition, such as iron planets, hyper-bony planets, chthonic planets, or mega-Earths.
The possibility of linking names to the essence or appearance of the planet is an inspiration for future naming campaigns, as long as they respect tradition and international standards.
Examples of iconic planets and exoplanets and their naming stories
We review some emblematic exoplanets, their circumstances of discovery and the origin of their names or designations:
- 51 Pegasi b: The first exoplanet discovered around a star like the Sun, nicknamed "Bellerophon" for its pioneering nature.
- HD 209458 b — Osiris: Named after the Egyptian god, it was the first exoplanet observed in transit, allowing its atmosphere to be directly studied.
- PSR B1620-26 b — Methuselah: One of the oldest planets, orbiting a dead star, hence its biblical name.
- Kepler-186f: First Earth-sized planet in the habitable zone of a star, an example of the importance of official designation systems.
- 2M1207 b: First planet photographed directly, in this case around a brown dwarf.
- TrES-4: Planet with the lowest known density, nicknamed for its rarity.
- Teegarden b: Considered the most potentially habitable exoplanet detected just 12 light-years away.
The future of exoplanet naming: challenges and opportunities
The massive discovery of exoplanets poses the challenge of maintaining a comprehensible, evocative, and diverse naming system. As technology advances, the number of known worlds is expected to continue to increase, opening the door to new public campaigns, the integration of as-yet-unexplored cultural references, and, hopefully, a progressively more inclusive and global nomenclature.
Exoplanet names will continue to evolve, reflecting not only scientific progress but also the pulse and aspirations of humanity, which has never stopped looking to the heavens for meaning.
