Saturn has smashed the record for the most moons in the solar system, and it was not even close. Astronomers have confirmed 128 new moons around the ringed planet, bringing its total to 274 and leaving Jupiter’s 95 trailing far behind. The discoveries were made using the Canada-France-Hawaii Telescope, in work led with researchers from the University of British Columbia, and have been formally recognised by the International Astronomical Union. Irish readers with a taste for sky-watching stories can also catch up on the SpaceX launch that created a jellyfish cloud over America.
Years of work behind one announcement
Behind the headline sits half a decade of unglamorous graft. The new moons are tiny, most no wider than a small town, and so faint that astronomers had to stack hundreds of telescope images together, each shifted to follow Saturn, before the moons emerged from the background glare. Every candidate then needed to be found again in later years so its orbit could be confirmed beyond doubt. It is the astronomical equivalent of a long investigation: hundreds of faint leads, checked and rechecked, until the evidence is strong enough to publish to the world.
Fragments of smashed worlds
Most of the newcomers travel in families, groups of fragments following similar tilted orbits far from Saturn’s equator. Scientists believe these families are the remains of larger moons or captured asteroids that were smashed apart in collisions, possibly in the relatively recent past by cosmic standards. Studying how the fragments have spread lets researchers work backwards to the impacts themselves, piecing together a history of destruction in the outer solar system. Some families may even preserve material that originated far beyond Neptune, captured by Saturn’s gravity during its youth.
A title that changed hands for good
For years the moon crown passed back and forth between Saturn and Jupiter as new surveys reported in. This announcement may settle the contest for a generation. Saturn’s tally is now nearly triple Jupiter’s, a gap no single survey of the larger planet is likely to close. Uranus and Neptune, with 29 and 16 moons, remain wildcards only because they are so distant and so lightly searched. Astronomers caution that the league table reflects observing effort as much as nature, but on any fair reading Saturn’s enormous gravitational reach has earned its title.
What the moons are good for
Beyond bragging rights, a full inventory of Saturn’s moons sharpens our picture of how the planet, and the solar system itself, was assembled. The balance between moons formed alongside Saturn and interlopers captured later is written in these orbits, and each confirmed family tests the computer models that describe the solar system’s violent early chapters. Future missions to the Saturn system will also navigate using this map. As results are analysed, expect detailed studies in journals such as {NAT} to argue over what the new population means for planetary history.
From myth to measurement
Saturn’s great moons carry names from Greek and Roman myth, Titans and giants whose stories were told for millennia before telescopes existed. The newest moons will largely take names from Norse, Inuit and Gallic traditions, continuing a convention that treats the planet’s family as a gathering of world mythologies. There is something fitting in that progression: the same planet that ancient storytellers watched as a slow, ominous wanderer is now measured by stacked digital images and orbital mathematics, yet still collects names from the old stories. The census may be modern science at its most rigorous, but it has not lost its sense of wonder, and neither should its readers.
More to come, almost certainly
The researchers are not pretending the book is closed. Their archives still contain candidates awaiting confirmation, and more sensitive instruments will find smaller moons yet. There is an open question about how tiny an object can be and still count as a moon rather than a piece of ring rubble, one the Union may eventually have to answer formally. For now, the figure to quote is 274, a number that would have seemed fanciful a generation ago, attached to a planet that keeps reminding us how much of our own neighbourhood remains undiscovered.