Astronomers have found three new moons orbiting our Solar System’s ice giants. One is orbiting Uranus, and two are orbiting Neptune. It took hard work to find them, including dozens of time exposures by some of our most powerful telescopes over several years. All three are captured objects, and there are likely more moons around both planets waiting to be discovered.
This is the first new moon found around Uranus in 20 years and brings the planet’s total to 28. One of the new moons around Neptune is the smallest ever detected with a ground-based telescope, and the pair of new discoveries bring Neptune’s total to 16.
Uranus’ new moon has the provisional title S/2023 U1 and was first observed on November 4, 2023, by Scott Sheppard from Carnegie Science. Like the planet’s other outer satellites, it will eventually be given a name from a Shakespeare play. Other moon names include Oberon, Titania, and Ariel. S/2023 U1 is only 8 km in diameter, tiny compared to the ice giant’s largest moon, Titania, which is almost 800 km. The tiny moon takes 680 days to orbit Uranus.
It’s time to add one more moon to Uranus’ tally. Tiny S/2023 U1 is the ice giant’s 28th moon. Image Credit: Canadian Space Agency.Neptune’s pair of new moons are likewise tiny. The brightest one has the provisional name S/2002 N5, is about 23 km in diameter, and takes nearly nine years to orbit Neptune. The fainter one has the provisional name S/2021 N1, is about 14 km in diameter, and takes almost 27 years to orbit the planet. They’ll both be given names from Greek mythology.
The newly discovered pair of tiny moons means Neptune now has 16 moons. All of the new moons are likely fragments from collisions that broke much larger moons apart early in the Solar System’s history. Image Credit: Canadian Space Agency.All of the easy-to-observe moons were found long ago. These small moons required much more work. While Scott Sheppard played a leading role, he had a lot of help.