Tiny new moons have been spotted orbiting Neptune and Uranus
Astronomers have found a new moon around Uranus and two orbiting Neptune – the first moons discovered orbiting these planets in a decade and the faintest ever spotted
By Leah Crane
23 February 2024
The planets Uranus (left) and Neptune (right) have a few additional moons
NASA, ESA, Mark Showalter (SETI Institute), Amy Simon (NASA-GSFC), Andrew I. Hsu, Michael H. Wong (UC Berkeley)
Astronomers have spotted new moons around Uranus and Neptune for the first time in a decade. These are the faintest moons ever spotted orbiting any planet, and they prove a long-standing idea about satellites in the outer solar system.
Scott Sheppard at the Carnegie Institution for Science in Washington DC and his colleagues found these moons using the Magellan telescope in Chile and confirmed them using several other large telescopes around the world. “We looked about four times deeper than anyone has before,” says Sheppard. “These moons are on the edge of our ability – they’re just faint, faint points of light.”
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Generally, when looking for moons, you can only take a picture with a maximum exposure of about 5 minutes before the image becomes overexposed and the movement of the moons makes it useless. Sheppard and his team got around this by taking many of these 5-minute images in a row, observing for hours and then combining the dim parts of the images. That enabled them to spot the dim points of light shining from the faintest moons ever discovered – and the smallest moons found to date around their respective planets.
The new moon around Uranus is provisionally named S/2023 U1, but it will eventually be given the name of a character in a Shakespeare play, to match the planet’s other moons. It is only about 8 kilometres across, and it completes an orbit once every 680 Earth days.
One of the new moons around Neptune is called S/2021 N1, and it awaits an official name from Greek mythology. It is about 14 kilometres across and takes about 27 Earth years to orbit the planet, making it the most distant moon from its host planet ever found. It is also the faintest moon ever found.
