The International Astronomical Union (IAU) has announced the results of a competition to find a name for Earth’s quasi-moon 2004 GU9. It was named Cardea, in honor of the Roman goddess of doors, doorways and thresholds.

Up to recently, the quasi-moons of the planets did not get their own names. That all changed after the curious story of Venus’ quasi-moon Zoozve. This object got such an unusual name because of the poor handwriting of the illustrator who created the solar system poster. He wrote out his official 2002 VE number and then misread his own handwriting. As a result, 2002 VE became Zoozve. The IAU later adopted this name as the official name.
Inspired by this story, writer and Radiolab science podcast host Latif Nasser proposed that the IAU organize a contest to find a name for Earth’s quasi-moon 2004 GU9. It is a 160-meter asteroid from the Apollo group that is in a 1:1 orbital resonance with our planet. This allows the asteroid to remain close to Earth for a long time. According to astronomers’ calculations, 2004 GU9 will be a quasi-moon of Earth until the year 2600, after which it will leave its vicinity.
The IAU endorsed Nasser’s idea. After receiving some 3,000 entries from more than 90 countries, the competition judges selected seven finalists. In accordance with IAU rules, all names were taken from the mythology of various cultures, from the Aztecs to the Inuit. The winner was selected in a vote organized on the Radiolab website. More than 10,000 people around the world took part in the voting.
Finally, the name of the Roman goddess of doors, Cardea, was the winner. It was suggested by American student Clay Chilcutt. He justified his choice as follows:
“A quasi-moon occupies a unique orbital path, existing in a transitional state between a true moon and an independent asteroid. [Cardea] symbolises change, guardianship, and the passage between realms. This name reflects the quasi-moon’s unique orbital path, embodying a celestial gateway between Earth and space.”
On January 13, 2025, the IAU Working Group on Small Body Nomenclature formally adopted Cardea as the official name of Earth’s quasi-moon.
According to IAU