How Many Moons Are In Our Solar System?


The moon you see in the night sky is just one of many moons in our solar system.

But exactly how many moons do we know about, and how many more could there be?

A Sky Full of Moons

There are hundreds, if not thousands, of natural satellites in our solar system, ranging from small, irregular space rocks to large, rounded bodies.

So, how many moons have we discovered so far? It depends on how you define a moon.

The International Astronomical Union (IAU) officially recognizes 288 planetary moons orbiting the eight major planets.

Additionally, NASA’s Jet Propulsion Laboratory lists 473 “small-body satellites,” which are moons of asteroids and dwarf planets.

Combined, this totals 761 known natural satellites as of June 2024.

But this is likely just the beginning. Astronomers are discovering new moons regularly, and advancements in technology are accelerating this process.

What Defines a Moon?

A simple definition of a moon is an object that orbits a larger, non-stellar body. However, this definition can be tricky.

For instance, human-made satellites orbit Earth but are not considered moons because they are artificial.

Some natural satellites, like quasi-moons and minimoons, are temporary and don’t truly orbit planets.

The size of the object also matters. Tiny particles that make up planetary rings are not considered moons, even though they orbit their planets.

Objects smaller than a few hundred feet, known as “ring moons” or “moonlets,” also aren’t counted as true moons.

Among recognized moons, there are regular moons (larger, circular orbits close to their planet’s equator) and irregular moons (smaller, elliptical orbits).

About 20 regular moons are considered major moons because they are large enough to be rounded by their own gravity.

Planetary Moons

Mercury and Venus, closest to the sun, have no true moons due to the sun’s gravitational pull. Venus does have one quasi-moon, Zoozve, but it orbits the sun, not Venus.

Earth has one major moon and at least seven quasi-moons, with occasional additional minimoons. Mars has two small moons, Phobos and Deimos, both only a few miles wide.

Jupiter has 95 moons, including the four large moons Callisto, Europa, Io, and Ganymede (the largest moon in the solar system). Saturn leads with at least 146 moons, including Titan, Mimas, and Enceladus.

Uranus and Neptune have 28 and 16 moons, respectively, with seven major moons between them.

Since 2023, astronomers have discovered at least 62 new moons around Saturn, 12 around Jupiter, and a few around Uranus and Neptune.

Small-Body Satellites

NASA counts 473 small-body satellites, but this number is uncertain and growing.

Many asteroids have moons, and there could be over 100 dwarf planets in the outer solar system, each potentially with its own moons.

The Future of Moon Discoveries

There are over 700 known natural satellites in the solar system, but this number is expected to grow.

More powerful telescopes will likely reveal hundreds, if not thousands, of tiny planetary moons.

Astronomer Edward Ashton estimates there could be around 10,000 moons in the solar system. However, finding them all could take a long time.