How do things in space get their names?

You may have heard the news about how the crew of NASA’s Artemis II mission named a crater on the Moon “Carroll.” The name honors Carroll Wiseman, the late wife of the mission’s commander, Reid Wiseman. It was a moving, heartfelt moment, showing how impactful it is that astronauts bring their full humanity into exploration. It might also make you wonder: who gets to name things in space, and how does it work?

The short answer is that every new name for a natural object in space is decided by the International Astronomical Union.

The long answer is much more interesting. 

Gods in the skies

The very first planetary bodies to be named were those visible to humans thousands of years ago, long before the International Astronomical Union (IAU) got involved. 

Aside from Earth, the Moon, and the Sun, which were given names in the earliest languages, the first planets to be named were those clearly visible in the night sky with the naked eye: Mercury, Venus, Mars, Jupiter, and Saturn. 

These planets have different names around the world, often linked to mythology. In some East Asian languages, their names relate to the five elements — Mercury as water, Venus as metal, Mars as fire, Jupiter as wood, and Saturn as earth. 

In English, as well as many European languages, the visible planets are named after Roman deities. This stems from ancient Greek culture, in which each planet was deemed sacred to a particular god based on compatible characteristics. The planet that moves across the sky the most quickly, for example, was associated with the swift messenger for the gods. The fiery red planet was associated with the angry god of war.

Ancient Roman culture adopted this tradition from the Greeks, assigning each planet to the corresponding god from their own mythology — Mercury, the messenger god; Mars, the god of war, etc. 

Because Roman culture and language dominated Europe for centuries, these names made their way into most modern European languages. 

New worlds, ancient names

When the telescope was invented, astronomers started finding new objects in need of names — moons of Jupiter and Saturn, the more distant planet Uranus, and more. 

At first, astronomers wanted to name their finds after the patrons who supported their work. Galileo Galilei wanted to name Jupiter’s four major moons, which he discovered in 1610, after the wealthy Medici family. When Giovanni Domenico Cassini spotted several of Saturn’s moons in the late 1600s, he called them Sidera Lodoicea ("Stars of Louis"), honoring King Louis XIV of France. In 1781, when William Herschel discovered Uranus, he wanted to name it after England’s King George III. 

But these names didn’t stick. Instead, the lasting names were those that aligned with the tradition of naming celestial objects after mythological figures. Jupiter’s moons were renamed after the lovers of the god Zeus (the Greek equivalent of Jupiter). Saturn’s moons were named after the Titans, the sisters and brothers of Kronos (the Greek version of Saturn). The seventh planet was dubbed Uranus (a variation of the name of the Greek god of the sky, Ouranos). 

And so, ancient mythology cemented its place in planetary science. 

Formalizing tradition

When the International Astronomical Union was established in 1919, it took on the responsibility of naming and cataloging celestial objects as well as surface features on planets, moons, asteroids, and comets. 

The IAU created some rules to guide its naming choices. One rule states that whenever possible, “the themes established in early Solar System nomenclature should be used and expanded on.” And so, as planets, moons, and other objects were discovered, they typically were assigned mythological names. 

The IAU didn’t insist on Greek or Roman mythology, though. In fact, their rules state that name choices should be diverse and equitable, representing names of all genders from ethnic groups and countries around the world. 

In the 2000s, several dwarf planets were discovered and given mythological names from cultures around the world, including Makemake, named after the creator god of the Rapa Nui people of Easter Island; Haumea, after the Hawaiian goddess of childbirth and fertility; and Sedna, after the Inuit goddess of the sea and marine animals. 

Throughout the Solar System, every planet, dwarf planet, and moon has a mythological name — almost. "Earth" derives from Old English and Germanic words meaning "ground" or "soil,” and the moons of Uranus are named after characters from the works of William Shakespeare and Alexander Pope. 

This happened because their discoverers named the first four moons after supernatural beings from English literature, rather than mythology. He chose Titania and Oberon from Shakespeare’s “A Midsummer Night’s Dream,” and Ariel and Umbriel from a poem by Pope (although Ariel is also a character in Shakespeare’s “The Tempest”). When more Uranian moons were found in later years, their discoverers just continued with names from Shakespeare. And so, in a Solar System filled with supernatural entities, we also have a moon named Juliet. 

Small things need names, too

When humans started sending spacecraft to study planetary bodies up close, we were able to identify mountains, rivers, plains, and other surface features — all of which needed names. 

The IAU states that official names shouldn’t be given to features less than 100 meters (328 feet) across, unless they’re of special scientific significance. Still, across all the planetary bodies of our Solar System, the IAU has approved more than 16,000 surface feature names to date. 

Typically, the teams working on the space missions that discover these features get to name them. This has led to some wonderfully nerdy naming conventions. When the NASA/ESA Cassini-Huygens mission to Saturn mapped its moon Titan, the team proposed names for hills and mountains drawn from J.R.R. Tolkien’s “The Lord of the Rings” series, and names for plains from Frank Herbert’s “Dune.” 

There are also more than 1.5 million asteroids and other small bodies cataloged in the Solar System — far too many to name. When an asteroid is discovered, it is typically given a technical designation based on the year and half-month it was discovered, and how many other asteroids were discovered in that same period. This is how you get names like asteroid 2024 YR4. 

But some asteroids are renamed, with approval from the IAU. Naming rules for asteroids are less strict, which allows their discoverers to suggest a range of names, including fun names like 88705 Potato and 2309 Mr. Spock (named after the discoverer's cat, not the Star Trek character).

Names for the people, by the people

Over several decades, The Planetary Society has run contests to engage the public in naming asteroids. This included a target for NASA’s Deep Space 1 mission, which was named Braille in 1999. And, more recently, partnering with the OSIRIS-REx team and the asteroid’s discoverer at MIT’s Lincoln Labs, a Planetary Society contest led to naming the asteroid target of NASA’s OSIRIS-REx mission. The winning name, Bennu, was suggested by an American nine-year-old, Mike Puzio, in 2013. Ten years later, Puzio was in attendance as the mission dropped a capsule in the Utah desert containing samples it had collected from the asteroid he had named. 

The IAU has also called for public suggestions to name exoplanets and the stars they orbit. Stars and exoplanets are often first assigned long, technical names based on the date and sequence of their discovery and cataloging. Since 2015, the IAU’s NameExoWorlds campaigns have solicited ideas from around the world to name dozens of stars and planets, with winning entries as diverse as the planets themselves.   

Campaigns to name other celestial objects continue to pop up from time to time. The podcast “Radiolab,” for example, worked with the IAU in 2024 on a campaign to rename (164207) 2004 GU9, a quasi-moon of Earth. The winning name, Cardea, earned more than 10,000 votes. 

Honor where honor is due

Even though Galileo and Cassini didn’t succeed in naming their discoveries after patrons and kings, some celestial objects today are still named after real people. Comets tend to be named after the person or team that discovered them, such as comet Shoemaker-Levy 9, which famously impacted Jupiter in 1994. It was the ninth comet discovered by the team of Carolyn and Gene Shoemaker and David Levy.

There are also surface features throughout the Solar System named for real people. Scientists and astronomers are the most common honorees, but so are artists, writers, musicians, and explorers. Nearly every surface feature on Venus — the only planet named after a woman — is named after a historic female figure, including Marie Curie, Florence Nightingale, Amelia Earhart, and others. 

While the IAU’s guidelines say that features should only be named after people of “high and enduring international standing,” sometimes an exception has to be made. During the Apollo 8 mission in 1968, astronaut Jim Lovell named a prominent lunar peak Mount Marilyn to honor his wife, who was waiting for him back on Earth. The IAU formally approved this name almost 50 years later, in 2017.

At the time of writing, “Carroll” hasn’t yet been formally approved by the IAU. But it will likely soon join the ranks of celestial names, making a lasting impact on our little part of the Cosmos.