In the red corner is Jupiter, the largest planet orbiting our sun, which formed our solar system with its gravitational pull.
In the blue corner is Saturn, the wonderfully circular world with puzzling hexagonal storms at its poles.
These two giant worlds are late in their bout of outsmarting satellites. But now the struggle over which planet has the most moons in orbit has swung decisively in favor of Saturn.
This month, the International Astronomical Union is set to recognize 62 more people Saturn’s moons Based on a collection of objects discovered by astronomers. The smaller bodies will give Saturn 145 moons – more than Jupiter’s total of 95.
“They both have many, many moons,” said Scott Sheppard, an astronomer from the Carnegie Institution for Science in Washington, D.C., but Saturn “appears to have a lot more moons” for reasons not fully understood.
The newly discovered moons of Saturn look nothing like the bright object in Earth’s night sky. They are irregular in shape, like a potato, and are no more than a mile or two wide. They orbit farther from the planet, too, between six million and 18 million miles, compared to larger moons, such as Titan, which orbit mostly within a million miles of Saturn. However, these small, irregular moons are fascinating in their own right. Mostly clustered together in clusters, they may be remnants of larger moons that were shattered during their orbits around Saturn.
“These moons are very key to understanding some of the big questions about the solar system,” said Bonnie Buratti of NASA’s Jet Propulsion Laboratory in California and deputy project scientist on the upcoming Europa Clipper mission to Jupiter. “They have the imprints of events that occurred in the early solar system.”
The increasing number of moons also highlights potential debates about what makes up the moon.
“The simple definition of a moon is that it is an object orbiting a planet,” said Dr. Sheppard. The size of the object, for now, doesn’t matter.
The new moons were discovered by two groups, one led by Dr. Sheppard and the other led by Edward Ashton of the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan. Dr. Sheppard’s group, in the mid-2000s, used the Subaru Telescope in Hawaii to search for more moons around Saturn.
In March, Dr. Sheppard was also in charge of the research 12 new moons of Jupiter, which temporarily took over Saturn in the ruckus to be the largest hoarder of the moons. This record was short-lived, it would seem.
dr ashton group, From 2019 to 2021, used the Canada France Hawaii Telescope, a neighbor of the Subaru Telescope on Mauna Kea, to search for more of Saturn’s moons and verify some of Dr. Sheppard’s discoveries. In order to authenticate the moon, it must be observed multiple times “to ensure that the observations are a satellite and not just an asteroid located near the planet,” said Mike Alexandersen, who is responsible for officially confirming the moons at International. Astronomical Union.
Most of Saturn’s irregular moons orbit the planet in what astronomers call the Inuit, Norse, and Gaulish groups. The objects of each group may be the remnants of larger moons, up to 150 miles across, that once orbited Saturn but were destroyed by impacts from asteroids or comets, or collisions between two moons. “It shows that there is a significant collision history around these planets,” said Dr. Sheppard.
Dr Ashton said these original moons may have been picked up by Saturn “very early in the solar system,” perhaps in the first few hundred million years after its formation 4.5 billion years ago. However, not all of these clusters orbit with a few rogue moons orbiting in a retrograde direction — that is, opposite the orbits of other moons.
“We don’t know what’s going on with those waning moons,” Dr. Sheppard said. Dr. Ashton suspects they may be remnants of a more recent collision.
It is difficult to learn more about new moons because of 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 not much is known.
“These things may be unique,” said Dr. Sheppard. “They may be the last remnants of what formed in the region of the giant planet, potentially very ice-rich bodies.”
NASA’s Cassini spacecraft was able to observe About twenty moons around Saturn until its demise in 2017. Although not close enough to study in detail, the data allowed scientists to “determine the period of rotation” of some moons, the axis of rotation and even the shape, said Tilmann Dink of the German Aerospace Center in Berlin, who Led notes. Cassini also found abundant ice on the surface One of the largest irregular moonsvibe.
Careful observations of Saturn’s small moons could give scientists a window into a turbulent time in the early solar system. During that period, collisions were more common and the planets scrambled for position, and Jupiter is thought to have migrated from its nearest sun to its current orbit. “This gives you additional information about the formation of the solar system,” said Dr. Dink.
However, the irregular moons we see so far may only be the beginning. “We estimate that there are potentially thousands,” said Dr. Ashton about Saturn and Jupiter. Uranus and Neptune may also have many of these irregular moons, but their vast distance from the Sun makes them difficult to spot.
Saturn, though smaller than Jupiter, appears to have a higher number of irregular moons. It may be three times the size of Jupiter, to about two miles in size. Dr Ashton said the reason is not clear.
Perhaps Jupiter’s original moons tend to be larger and less prone to breakage. Or, Saturn may have captured more objects in its orbit than Jupiter. Or perhaps Saturn’s moons had orbits that were likely to overlap and collide, producing smaller, irregular moons.
Whatever the reason, the result is clear. Jupiter is about to collapse, and it is unlikely that it will regain its title as the planet with the most moons. As astronomers’ abilities to find smaller and smaller satellites improve, “Saturn will win by miles,” Dr. Alexandersen said. “I don’t think it’s a contest anymore.”