Three tiny new moons found around Uranus and Neptune
Astronomers have discovered two tiny moons orbiting Neptune and one circling Uranus, bringing the number of their known moons up to 16 and 28 respectively. Uranus’ new moon, the first detected around the ice giant in over two decades and possibly the smallest of its ilk, is just eight kilometres (five miles) wide; it takes 680 days to complete one orbit around Uranus. In comparison, one of Mars’ moons, Deimos, considered to be among the tiniest known moons in our Solar System, is 13 kilometres (eight miles) wide. The new moon of the blue-green planet is currently referred to as ‘S/2023 U1’ while it awaits being named after a Shakespearean character.
The brighter of Neptune’s two new moons is provisionally named ‘S/2002 N5’. At 23 kilometres (14 miles) wide, this newly discovered satellite seems to be in a nine-year orbit around Neptune. The fainter moon, ‘S/2021 N1’, is 14 kilometres (8.6 miles) wide and circles Neptune once every 27 years. Both Neptunian moons will be assigned permanent names based on sea gods and nymphs in Greek mythology.
The three new moons were announced on 23
February by the International Astronomical Union’s Minor Planet Center, a Massachusetts-based scientific body responsible for designating planets, comets and moons in our Solar System. The discoveries were made using observatories in Hawaii and Chile by Scott Sheppard, a staff scientist at Carnegie Science, in collaboration with Marina Brozovic and Bob Jacobson of NASA’s Jet Propulsion Laboratory, David Tholen of the University of Hawaii, Chad Trujillo of Northern Arizona University and Patryk Sofia Lykawka of Kindai University.
The new moons are “the faintest ever found around these two ice giant planets using groundbased telescopes,” Sheppard said. “It took special image processing to reveal such faint objects.” He first detected the new Uranian moon in November of 2023 while using Chile’s Magellan telescopes. A month later, follow-up observations combined with Jet Propulsion Laboratory scientists’ predictions of a possible orbit for the new moon confirmed the find. The two new residents in Neptune’s moon system were first seen in September 2021. After the orbit of the brighter of the two natural satellites was confirmed, “it was traced back to an object that was spotted near Neptune in 2003, but lost before it could be confirmed as orbiting the planet,” said Sheppard.
Determining the orbit of the fainter Neptunian moon “required special observing time under ultra-pristine conditions” with Europe’s Very Large Telescope in Chile and the Gemini Observatory in Hawaii.
Using these telescopes, Sheppard and his colleagues clicked a series of fiveminute exposures over three to four-hour periods. These short-burst images were later ‘layered’ in such a way that the three newfound moons came into clearer view. All three moons have egg-shaped orbits highly inclined to the plane of their respective ice giant. This implies they did not birth around their host planet but were instead gravitationally seized later on.
“It took special image processing to reveal such faint objects” Scott Sheppard