The Moon does not qualify as a planet because it orbits Earth instead of the Sun [1].
This distinction clarifies the technical boundary between planets and satellites, reinforcing the rigid standards used by astronomers to categorize celestial bodies.
The International Astronomical Union (IAU) established three specific criteria for a body to be classified as a planet in 2006 [1]. According to the IAU, a planet must orbit the Sun, possess sufficient mass for self-gravity to create a nearly round shape, and have cleared the neighborhood around its orbit [1].
While the Moon is massive enough to be round and satisfies two of these three criteria [2], it fails the first requirement [2]. Because the Moon exists within the Earth-Moon system and orbits the Earth, it cannot be classified as a planet under current rules [2].
"The Moon meets two of the three IAU criteria for a planet, but it fails the first because it orbits Earth, not the Sun," Henry Reich said [2].
The IAU definition was designed to create a consistent framework for solar system classification [1]. By requiring a direct orbit around the Sun, the organization distinguishes primary planets from moons, and other satellites that orbit larger bodies [1, 2].
“The Moon meets two of the three IAU criteria for a planet, but it fails the first because it orbits Earth, not the Sun.”
The classification of the Moon as a satellite rather than a planet highlights the IAU's priority on orbital dynamics over physical characteristics. While the Moon shares the spherical shape and mass of a planet, the requirement of a primary solar orbit ensures that the term 'planet' is reserved for the dominant bodies of the solar system, maintaining a clear hierarchy in astronomical taxonomy.
