The solar system contains many more moons than the one visible from Earth. But how many do we actually know about, and how many more are waiting to be discovered?
Saturn has at least 146 moons, the most of any planet in the solar system. If you look up on a clear night, the brightest and largest object you will see is the moon. Without a telescope, it’s the only natural satellite visible to the naked eye, leading to a common misconception about the prevalence of moons. In reality, our cosmic neighborhood hosts hundreds, if not thousands, of natural satellites, ranging from small space rocks to large, round bodies that could be considered planets.
So, how many moons have we found in the solar system? According to NASA, the International Astronomical Union (IAU) officially recognizes 288 planetary moons orbiting the solar system’s eight planets. Additionally, NASA’s Jet Propulsion Laboratory lists 473 “small-body satellites” — moons of asteroids and dwarf planets. Counting both types, there are 761 known natural satellites in the solar system as of June 2024.
This is likely just the beginning, says Edward Ashton, an astronomer at the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan. Technological advancements are expected to increase the rate of moon discoveries in the coming years.
Defining a moon can be tricky. The simplest definition is an object orbiting a larger, non-stellar body. However, artificial satellites and temporary natural satellites like quasi-moons and minimoons complicate this definition.
Mercury and Venus have no true moons due to their proximity to the sun, which would have stripped away any moons. Earth has one major moon, along with several quasi-moons and temporary minimoons. Mars has two small moons, Phobos and Deimos, which orbit very close to the planet.
Jupiter, the first gas giant, has 95 moons, including four major ones: Callisto, Europa, Io, and Ganymede. Saturn boasts 146 moons, including six major ones like Titan, Mimas, and Enceladus. The ice giants Uranus and Neptune have 28 and 16 moons, respectively.
Recent discoveries have added numerous moons to these counts. Since the start of 2023, astronomers have found 62 new irregular moons around Saturn, 12 new moons around Jupiter, and several new moons around Neptune and Uranus.
The number of moons is expected to continue rising as more powerful telescopes reveal smaller and more distant satellites. Ashton believes there could be around 10,000 moons in the solar system, though it may take a long time to find them all.
