Moons of Our Solar System

Moons come in many shapes, sizes, and types. A few have atmospheres and even hidden oceans beneath their surfaces.

One of the moons in our solar system

How Many Moons Are in Our Solar System?

Naturally-formed bodies that orbit planets are called moons, or planetary satellites. The best-known planetary satellite is, of course, Earth’s Moon. Since it was named before we learned about other planetary satellites, it is called simply “Moon.”

A plane is seen flying in front of the Moon on July 31, 2015, in Arlington, Virginia.
NASA/Joel Kowsky

According to the NASA/JPL Solar System Dynamics team, the current tally of moons orbiting planets in our solar system is 293: One moon for Earth; two for Mars; 95 at Jupiter; 146 at Saturn; 28 at Uranus; 16 at Neptune; and five for dwarf planet Pluto.

Astronomers also have documented more than 470 satellites, or moons, orbiting smaller objects, such as asteroids, dwarf planets, or Kuiper Belt Objects (KBOs) beyond the orbit of Neptune. These moons are called small-body satellites.

Most planetary moons probably formed from the discs of gas and dust circulating around planets in the early solar system, though some are captured objects that formed elsewhere and fell into orbit around larger worlds.

Scientists are very good at spotting tiny moons orbiting distant, giant planets. So many tiny moons have been found that the International Astronomical Union, which governs official names of planets and moons, will no longer name the smallest moons unless they’re of “significant” scientific interest. There are likely thousands more moons awaiting discovery in our solar system.

NASA – Pluto and Its Moons: Charon, Nix and Hydra

A pair of small moons orbiting Pluto, which were discovered by NASA’s Hubble Space Telescope

Discovered in 2005, the two moons are roughly 5,000 times fainter than Pluto and are about two to three times farther from Pluto than its large moon, Charon, which was discovered in 1978.

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Pluto's moons, Charon, Nix and Hydra
A pair of small moons that NASA’s Hubble Space Telescope discovered orbiting Pluto now have official names: Nix and Hydra. Photographed by Hubble in 2005, Nix and Hydra are roughly 5,000 times fainter than Pluto and are about two to three times farther from Pluto than its large moon, Charon, which was discovered in 1978.

Hubble Discovers a Fifth Moon Orbiting Pluto

A team of astronomers using NASA’s Hubble Space Telescope is reporting the discovery of another moon orbiting the icy dwarf planet Pluto.

The moon is estimated to be irregular in shape and 6 to 15 miles across. It is in a 58,000-mile-diameter circular orbit around Pluto that is assumed to be co-planar with the other satellites in the system.

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Hubble image of Pluto and its moons
This image, taken by NASA’s Hubble Space Telescope, shows five moons orbiting the distant, icy dwarf planet Pluto. The green circle marks the newly discovered moon, designated P5, as photographed by Hubble’s Wide Field Camera 3 on July 7. The observations will help scientists in their planning for the July 2015 flyby of Pluto by NASA’s New Horizons spacecraft. P4 was uncovered in Hubble imagery
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