In the red corner is Jupiter, the largest planet orbiting our Sun, which has shaped our solar system with its gravitational mass.

In the blue corner is Saturn, a magnificent ringed world with stunning hexagonal storms at the poles.

These two gigantic worlds are overdue in the struggle for satellite-based dominance. But now the battle over which planet has the most moons in its orbit has turned decisively in Saturn’s favor.

This month, the International Astronomical Union intends to recognize 62 more satellites of Saturn based on a series of objects discovered by astronomers. Small objects would give Saturn 145 moons, dwarfing Jupiter’s 95.

“They both have many, many satellites,” said Scott Sheppard, an astronomer at the Carnegie Institution of Science in Washington, DC.

The newly discovered moons of Saturn look nothing like a bright object in Earth’s night sky. They are irregularly shaped, like potatoes, and no more than a mile or two across. They also orbit far from the planet, between six million and 18 million miles, compared to larger moons like Titan, which mostly orbit within a million miles of Saturn. However, these little irregular moons are charming in their own right. They are mostly clustered and may be the remnants of larger moons that crashed while orbiting Saturn.

“These moons are key to understanding some important questions about the solar system,” said Bonnie Buratti of NASA’s Jet Propulsion Laboratory in California and deputy project scientist for the upcoming Europa Clipper mission to Jupiter. “They have fingerprints of events that took place in the early solar system.”

The growing number of moons is also highlighting a potential debate about what constitutes a moon.

“A simple definition of a moon is that it’s an object that orbits a planet,” says the doctor. Sheppard said. The size of the object doesn’t matter at the moment.

The new moons were discovered by two teams, one led by Dr. J. Sheppard and the other recently made by Edward Ashton of the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan. Dr. Sheppard’s team in the mid-2000s used the Subaru telescope in Hawaii to search for additional satellites around Saturn.

In March Dr. Sheppard was also responsible for discovering 12 new moons of Jupiter, which temporarily topped Saturn in the fray to become the biggest hoarder of moons. This entry appears to have been short-lived.

doctor Ashton Group, from 2019 to 2021, used the Canadian-French Hawaiian Telescope, a neighbor of the Subaru Telescope on Mauna Kea, to find more moons of Saturn and check out some of the doctor’s moons. Sheppard’s discoveries. To authenticate a moon, it needs to be detected multiple times to “be sure it’s a satellite and not just an asteroid that happens to be near the planet,” said Mike Alexandersen, who is responsible for officially confirming moons at the International Astronomical Union.

Most of Saturn’s irregularly shaped moons orbit the planet in what astronomers call the Inuit, Scandinavian, and Gaulish groups. Objects in each group could be the remnants of larger moons up to 150 miles in diameter that once orbited Saturn but were destroyed by asteroid or comet impacts or by collisions between two moons. “This shows that there has been a large history of collisions around these planets,” says the doctor. Sheppard said.

These primordial moons may have been captured by Saturn “very early in the solar system.” Ashton said perhaps in the first few hundred million years after its formation 4.5 billion years ago. However, not all orbits in these groups, with several rogue satellites, rotate in a retrograde direction, that is, in the opposite direction to the orbits of other satellites.

“We don’t know what’s going on with these retrograde moons,” the doctor says. Sheppard said. Dr. Ashton suspects that these may be remnants of a recent collision.

Learning more about new moons is difficult due to their small size and distant orbits. It appears to be a special class of objects, distinct from asteroids formed in the inner solar system and comets in the outer solar system, but little is known.

“These objects can be unique,” ​​says the doctor. Sheppard said. “They may be the last remnants of what formed in the region of the giant planet, probably very ice-rich objects.”

NASA’s Cassini spacecraft observed about two dozen moons around Saturn until its death in 2017. Although these data are not close enough to study in detail, they have allowed scientists to “determine the period of rotation” of some satellites, the axis of rotation, and “even the shape,” Tilmann Denk said. from the German Aerospace Center in Berlin, who directed the observations. Cassini also found a lot of ice on the surface one of the largest irregular moonsPhoebe.

Closer observation of Saturn’s tiny moons could give scientists a glimpse into turbulent times in the early solar system. Collisions were more frequent during this period, and the planets fought for position, and Jupiter was thought to have migrated from closer to the Sun further to its current orbit. “This gives you additional information about the formation of the solar system,” says the doctor. Think said.

However, the irregular moons we see so far may only be the beginning. “We calculated that there could potentially be several thousand of them,” around Saturn and Jupiter. Ashton said. Uranus and Neptune may also have many of these irregular moons, but their great distance from the Sun makes them difficult to spot.

Saturn, despite being smaller than Jupiter, has many more irregular moons. It may have three times the size of Jupiter and is about two miles across. The reason is unclear, doctor. Ashton said.

Jupiter’s original moons may have tended to be larger and less likely to collapse. Or Saturn may have captured more objects into its orbit than Jupiter. Or Saturn’s moons may have been in orbits that were more likely to overlap and collide, creating smaller, irregular moons.

Whatever the reason, the result is clear. Jupiter is on the brink and is unlikely to regain the title of the planet with the most moons. As astronomers’ ability to find smaller and smaller moons improves, “Saturn will win by miles,” says the doctor. Alexandersen said. “I don’t think it’s more of a competition.”