Jupiter now has 'most moons' in solar system

In addition to being the biggest and most massive planet in the solar system, Jupiter now has the most moons around it, at 92, making the gas giant the largest body in the solar system overall.

According to a recent article from Sky and Telescope, the Minor Planet Centre (MPC), run by the Smithsonian Astrophysical Observatory, has revealed the orbits of the 12 unidentified moons of Jupiter. With these recent discoveries, Jupiter has surpassed Saturn to claim the title of "planet in the solar system with the most moons."

Around the ringed gas giant, the second-largest planet in the solar system, researchers have discovered 83 moons so far. But according to Sky and Telescope, astronomers have also discovered tonnes of rocks up to around 2 miles (3 kilometres) wide near Saturn without yet properly tracking the objects. Jupiter may have to give back its new title to Saturn as soon as technology allows for the study of these smaller moons.

The observations of the Jovian system, made in 2021 and 2022, have been submitted for publication by Scott Sheppard, an astronomer at the Carnegie Institute for Science in Washington, DC, reported Space. The reason for the gap between the discovery of the new moons and their confirmation is that astronomers had to follow the pebbles for a full orbit to make sure they were indeed orbiting Jupiter.

According to Sky and Telescope, all of the new moons orbit Jupiter at a distance from its surface, taking more than 340 Earth days to do so. Nine of the 12 new moons are extremely far away. Their orbits are longer than 550 days. All of these moons are small; just five of those nine moons are believed to have a diameter larger than five miles (8 km).

The outer Jovian moons, in contrast, have "prograde" orbits that circle the gas giant in the same direction as the planet's spin. The nine moons that are very far away have retrograde orbits, which means that they circle the gas giant in the opposite direction from its rotation. The retrograde orbits of the new moons suggest that Jupiter's powerful gravitational pull may have grabbed these moons, with the smaller ones perhaps being the fragments of larger entities that collided and broke apart.

The prograde orbits of some of the recently discovered moons indicate that they developed around Jupiter. Io, Europa, Ganymede, and Callisto are the large inner moons that are known as the Galilean moons because they were first discovered by Galileo Galilei in the early 1600s. These prograde orbiting moons are situated in a middle swath of space with 13 other Jovian moons.