The question of whether Earth’s Moon is larger than Pluto is a common point of confusion when exploring the Solar System’s celestial objects. This comparison highlights the surprising scale and diversity among moons and dwarf planets. Many people assume Pluto must be bigger because it once held the title of a planet. Answering this query requires a look at the precise dimensions of both worlds and the unique classifications that define them.
Comparing the Dimensions of the Two Bodies
The definitive answer is that Earth’s Moon is substantially larger than Pluto. The Moon’s mean diameter measures approximately 3,475 kilometers (2,160 miles). By contrast, the dwarf planet Pluto has a diameter of about 2,370 kilometers (1,473 miles), confirmed by data from the New Horizons mission.
The Moon is roughly 1,100 kilometers wider than Pluto, making it about one-third larger in diameter. Pluto is smaller than several other moons in the Solar System, including Jupiter’s Ganymede and Saturn’s Titan. The Moon is the fifth-largest natural satellite overall, easily surpassing the size of the largest known dwarf planets.
Why Pluto is a Dwarf Planet
Pluto’s small stature contributed to the International Astronomical Union (IAU) reclassifying it as a dwarf planet in 2006. The IAU established three specific conditions a celestial body must meet to be considered a full planet.
First, the object must orbit the Sun, which Pluto does. Second, it must have enough mass for its gravity to pull it into a nearly round shape, a state known as hydrostatic equilibrium. Pluto meets this criterion, which is why it is not simply classified as a small Solar System body.
Pluto fails to meet the third condition: it has not “cleared the neighborhood” around its orbit. This means its mass is insufficient to gravitationally dominate its orbital path, which is shared with many other large objects in the Kuiper Belt.
The Unusually Large Size of Earth’s Moon
The Moon’s size relative to its host planet makes it a remarkable object in the Solar System. Earth’s Moon has a diameter that is about 27% the diameter of Earth itself. This ratio is exceptionally high when compared to the moons of other planets.
The Moon’s mass is also unusually high, measuring roughly 1/81st of Earth’s total mass. For comparison, the largest moon orbiting Jupiter, Ganymede, accounts for only about 1/10,000th of Jupiter’s mass. Because of this relatively large size and mass, the Earth-Moon system is sometimes referred to as a “double planet” system.
The gravitational influence of the Moon is so strong that the center of mass for the pair, called the barycenter, is not at the geometric center of Earth. Instead, the barycenter lies about 1,700 kilometers beneath Earth’s surface. This causes both bodies to orbit this common point, highlighting the Moon’s large absolute size compared to Pluto.