How Did Dwarf Planet Eris Get Its Name

Dwarf planet Eris got its name from Eris, the Greek goddess of discord and strife. The choice was deliberate: Eris’s discovery ignited a fierce argument over whether Pluto should remain a planet, making the goddess’s troublesome reputation feel almost uncomfortably appropriate.

The object was first nicknamed “Xena” by the discovery team, after the television heroine played by Lucy Lawless. That was never its official name. On September 14, 2006, the International Astronomical Union approved “Eris” for the distant solar system object, which received the minor-planet designation 136199 Eris. Its moon was named Dysnomia, after the goddess of lawlessness and daughter of Eris, with a quiet nod to Lawless herself.

What Does the Name Eris Mean?

Greek Goddess

In Greek mythology, Eris personifies discord, rivalry, and strife. She is often portrayed as a disruptive figure who introduces conflict into gatherings that might otherwise remain peaceful. The Roman equivalent is Discordia.

That mythological connection mattered because the new dwarf planet appeared during an already unsettled period in planetary astronomy. Astronomers had found a large, distant body beyond Neptune, and its discovery raised an awkward question: if Eris was larger or at least more massive than Pluto, should it also be called a planet?

The name carried that tension elegantly. As the International Astronomical Union’s announcement made clear, the mythological reference was more than decoration.

Discord and Strife

The research team’s temporary name, Xena, helped distinguish the object during years of observation and discussion. It came with its own satellite nickname, Gabrielle. Those informal labels were useful, especially while the object still carried the provisional designation 2003 UB313, but they belonged to the discovery process rather than the permanent astronomical record.

Mike Brown later proposed Eris because the object had caused such disruption in planetary classification. The name Xena had public appeal, particularly among science-fiction fans, yet Eris had deeper historical weight. It connected the celestial body to the very dispute it had helped create.

Mythological Symbolism

Dysnomia’s name extends the same symbolism. In mythology, Dysnomia represents lawlessness, which suits a moon orbiting an object that unsettled the “law” of the solar system’s planetary order. The name also preserved the playful connection to Lucy Lawless without turning a scientific designation into a television reference.

Names in planetary astronomy often reach back to mythology, but Eris feels unusually self-aware. The name describes the object’s cultural effect as much as its mythological identity.

How Did Eris Get Its Official Name?

Discovery Announcement

Astronomers identified Eris in January 2005 while examining images taken in 2003 during a Palomar Observatory survey of distant objects. The discovery involved Mike Brown, Chad Trujillo, and David Rabinowitz. NASA’s Eris profile records the timeline from the original observations to the eventual naming.

The object’s size quickly made it important. Eris was clearly a major trans-Neptunian body, orbiting in the scattered disk beyond Neptune. Its discovery revived the idea that the solar system might contain a “10th planet,” especially since Pluto’s status had never been as secure as schoolroom diagrams suggested.

Naming Proposal

While the team used Xena internally, the formal naming process followed astronomical convention. A discoverer can suggest a name, but the IAU evaluates and approves names through its planetary nomenclature system.

Brown proposed Eris after the object’s discovery had triggered arguments among astronomers, historians, and the public. His personal discovery logs preserve some of the informal history behind Xena and the satellite’s earlier nickname.

International Approval

The IAU Working Group for Planetary System Nomenclature unanimously accepted Eris and Dysnomia in September 2006. The Caltech account of the naming describes how the temporary television-inspired name gave way to the Greek mythological choice.

The official designation also became 136199 Eris. In other words, Eris has both a proper name and a planet number, as do many recognized minor planets.

Who Discovered the Dwarf Planet?

Palomar Observatory

The discovery came from a wide-field survey using the Samuel Oschin Telescope at Palomar Observatory in California. Finding Eris required comparing images and detecting the slow movement of a faint object against the background stars. It was careful survey work, not a single dramatic telescope photograph.

Mike Brown

Astronomer Michael E. Brown of Caltech led the discovery team. His work focused on distant bodies beyond Neptune, including several objects that helped reveal how populated the outer solar system really is.

Chad Trujillo and David Rabinowitz

Chad Trujillo, then associated with the Gemini Observatory, contributed to the observations and analysis. David Rabinowitz of Yale also played a central role. Discovery credit belongs to the team, even though Brown became Eris’s most publicly recognized discoverer.

Why Is Eris Classified as a Dwarf Planet?

The IAU defines a dwarf planet as an object that orbits the Sun, is massive enough for gravity to make it nearly round, and has not cleared the neighborhood around its orbit. Eris meets the first two conditions, but it shares the distant region beyond Neptune with other small bodies.

That last point is decisive. Eris is in hydrostatic equilibrium, meaning its gravity has pulled it into a rounded shape, but it does not dominate its orbital zone the way Earth, Jupiter, or Neptune does. “Dwarf planet” is therefore a formal classification, not a casual insult or a claim that Eris is merely a large asteroid.

How Did Eris Change Pluto’s Status?

Eris did not single-handedly “demote” Pluto, although public language often makes it sound that way. Its discovery exposed a classification problem: either Eris and several other distant bodies might become planets, or astronomers would need a clearer definition of planethood.

In 2006, the IAU adopted a three-part definition of a planet and created the dwarf-planet category. Pluto, Eris, and other rounded bodies were placed in that category because they have not cleared their orbital neighborhoods. The decision remains culturally controversial, but scientifically it gave planetary astronomy a workable vocabulary.

As contemporary reporting from The New York Times captured, Eris became famous because it forced the argument into the open.

What Are Eris’s Key Physical Features?

Eris is an extremely distant scattered-disk object with a highly elongated orbit. It can travel roughly 14.6 billion km from the Sun at its farthest point and comes to about 5.7 billion km at perihelion. One trip around the Sun takes approximately 557 Earth years.

Its diameter is about 2,326 km, making it close in size to Pluto. Eris has a bright, reflective surface likely coated with frozen nitrogen and methane, and its single known moon, Dysnomia, helps astronomers estimate the dwarf planet’s mass.

The Britannica overview of Eris places these features in the broader story of trans-Neptunian planetary science.

FAQ

Was Eris ever officially called Xena?

No. Xena was an informal nickname used by the discovery team before the IAU approved the name Eris.

Is Eris bigger than Pluto?

Eris is slightly more massive than Pluto, while their diameters are very similar. Measurements have become more precise through stellar occultations and other observations.

Why was Eris named after a goddess of discord?

Because its discovery provoked a major dispute over the definition of a planet and Pluto’s classification. The mythological name reflected that scientific turmoil.

Conclusion

Eris got its official name because its discovery disturbed the neat planetary picture people had inherited. The Greek goddess of discord was an unusually fitting choice for a world that helped rewrite the rules of planethood. Xena made a memorable nickname, but Eris became the name that history kept.