The newly identified moons are among the smallest and darkest celestial bodies within the Solar System, making their detection a considerable challenge for astronomers. Typically, these distant, natural satellites are difficult to observe due to their diminutive size and low reflectivity.
Uranus and Neptune, the Solar System's furthest and least explored planets, continue to surprise the scientific community. Prior to this discovery, Uranus was known to have 27 moons, and Neptune had 14, with the latter's last moon, Hippocamp, discovered in 2013.
The discovery was led by Dr. Scott S. Sheppard of the Carnegie Institution for Science in Washington, USA. "The three newly discovered moons reflect the least amount of light among all celestial objects discovered around the two ice giants to date, requiring advanced image processing for their detection," Dr. Sheppard explained.
A faint, moving speck of light in photographs taken using the Magellan telescopes at the Las Campanas Observatory in Chile, both in November 2023 and two years prior, hinted at a new moon orbiting Uranus. The continuous movement of this speck across several nights, visible only through overlapping images from different evenings, confirmed its nature as a Uranian satellite.
Designated S/2023 U1, this new Uranus moon measures approximately 5 miles in diameter and follows a distinctive, eccentric orbit. Completing an orbit around Uranus takes about 680 days. In line with tradition, it will soon receive a name from a character in William Shakespeare's plays or the works of Alexander Pope, joining the likes of Titania, Uriel, Ariel, and Miranda.
The two Neptune moons, identified in 2021 via the Magellan and Japanese Subaru telescopes, add further intrigue. One, preliminarily termed S/2002 N5, has a 14-mile diameter and completes an orbit in nearly nine years. The other, S/2021 N1, is about 9 miles across and orbits Neptune every 27 years. Both moons are expected to be named following the tradition of using names of Nereids, Greek mythology's sea nymphs.
These discoveries underscore the organized moon systems of the outer planets, consistent with the small, icy satellites that typically inhabit inclined orbits. According to Dr. Sheppard, the unique orbits of these moons suggest they are remnants of larger bodies, initially captured by the gravity of Uranus and Neptune and later fragmented by collisions.
This addition brings to light the possibility of even more undiscovered minor moons orbiting these distant giants, contributing to the over 200 moons now cataloged in our Solar System. Dr. Scott S. Sheppard's contributions to celestial discoveries, including the identification of multiple moons, asteroids, and comets, have been widely recognized, with an asteroid named (17898) Scottsheppard in his honor.
