Jupiter officially has the most moons in the solar system, discovery of 12 new satellites confirms

Jupiter was already the king of the solar system, and new discoveries give the massive planet another way to reign supreme: It now has the most moons.

Twelve new moons discovered orbiting Jupiter have been confirmed, bumping the count from 80 to 92, and knocking Saturn — which has 83 moons — down a peg. 

The newly discovered moons are small, ranging from 0.6 to 2 miles (1 to 3.2 kilometers) wide, and most of them have wide orbits. Nine of the 12 moons take more than 550 days to orbit the gas giant, Sky and Telescope reported (opens in new tab). These far-out moons also orbit Jupiter in a retrograde motion, meaning they move in the opposite direction of Jupiter's rotation. Their distant and retrograde orbits likely mean these objects used to be asteroids and eventually got caught up in Jupiter's gravity, according to the researcher who detected them. 

The moons were discovered in 2021 and 2022 by Scott Sheppard (opens in new tab), an astronomer at the Carnegie Institution for Science in Washington, D.C. He reported his findings to the International Astronomical Union's Minor Planet Center, which tracks all reports of small bodies in the solar system. Before the moons could be officially confirmed, their complete orbits had to be tracked, according to Sky and Telescope. Now, all 12 have officially been confirmed.

Jupiter's best-known natural satellites are its four Galilean moons, named after astronomer Galileo Galilei, who observed them in 1610. They include Io, with its lava lakes and enormous volcanic eruptions; Europa, with its icy shell and inner water ocean; Ganymede, the largest moon in the solar system (it's larger than Mercury, according to NASA (opens in new tab)); and Callisto, the most cratered moon in the solar system. 

This year, the European Space Agency's Jupiter Icy Moons Explorer (opens in new tab) (known as JUICE) is set to launch toward the gas giant to explore these four moons, and in 2024, NASA's Europa Clipper is slated to launch on a mission to get a closer view of Europa.