Uranus’s new moon, S/2025 U1, was spotted using the James Webb Space Telescope
NASA/ESA/CSA/STScI/M. El Moutamid (SwRI)/M. Hedman (University of Idaho)
This year, astronomers discovered more than 100 previously unknown moons in our own solar system. There may be many more yet to be discovered, and cataloguing them could help us better understand how planets form.
In March, Edward Ashton at Academia Sinica in Taiwan and his colleagues discovered 128 moons around Saturn, bringing the planet’s total to 274. The team gathered hours’ worth of images from the Canada-France-Hawaii Telescope in Hawaii and stacked them on top of each other to spot objects that are otherwise too dim to see.
Ashton’s team now has the right to name the new moons, although Saturn’s moons are so numerous that many are no longer given informal names.
In August, a small and dim new moon was found in orbit around Uranus, bringing the planet’s total to 29. Maryame El Moutamid at Southwest Research Institute in Colorado and her colleagues made the discovery using 10 long-exposure infrared images taken by NASA’s James Webb Space Telescope.
The team remains tight-lipped on potential names for the moon, so it still has the provisional name S/2025 U1. In time, it will probably be named along the same lines as 27 of Uranus’s moons, which take a character’s name from one of Shakespeare’s plays. This convention dates back to the discovery of the planet’s first two moons, Titania and Oberon, in 1787.
Nigel Mason at the University of Kent, UK, says there are likely to be many more moons to be discovered in our solar system, particularly around Neptune and Uranus, although the largest ones have probably already been mapped.
“Everybody always likes to find new moons and everybody always likes to think about what they’re going to call them,” he says. “It’s an exciting moment. It’s a bit of a legacy.”
The more we catalogue and measure our local moons, the more we can find out about how they are created and use that information to update our models of planet formation, says Mason.
“Why are there so many? What is it that triggered [planets] to make 40, 50, 60 of such varying shapes and sizes? That’s why they’re exciting,” he says. “It’s not just stamp collecting. It really is ‘wow’. Really surprisingly, the whole planet-formation process is not as well as understood as we think.”
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