New Moons of Uranus and Neptune from Ultra-Deep Pencil Beam Surveys
Scott Sheppard, David Tholen, Marina Brozovic, Robert Jacobson,, Chadwick Trujillo, Patryk Sofia Lykawka, Mike Alexandersen

TL;DR
This study used ultra-deep imaging to discover new moons around Uranus and Neptune, revealing dynamical groups and suggesting satellite fragmentation, which enhances understanding of outer satellite populations and their origins.
Contribution
The paper reports the discovery of three new moons around Uranus and Neptune using ultra-deep surveys, and analyzes their dynamical groups and size distributions, providing new insights into satellite formation and evolution.
Findings
Three new moons discovered around Uranus and Neptune.
Dynamical groups of moons identified around both planets.
Size distribution shows steepening below 5 km, indicating collisional break-up.
Abstract
We have conducted extremely ultra-deep pencil beam observations for new satellites around both Uranus and Neptune. Tens of images on several different nights in 2021, 2022 and 2023 were obtained and shifted and added together to reach as faint as 26.9 and 27.2 magnitudes in the r-band around Uranus and Neptune, respectively. One new moon of Uranus, S/2023 U1, and two new moons of Neptune, S/2021 N1 and S/2002 N5, were found. S/2023 U1 was 26.6 mags, is about 7 km in diameter and has a distant, eccentric and inclined retrograde orbit similar to Caliban and Stephano, implying these satellites are fragments from a once larger parent satellite. S/2023 U1 almost completely overlaps Stephano in orbital phase space. S/2021 N1 was 26.9 mags, about 14 km in size and has a retrograde orbit similar to Neso and Psamathe, indicating they are a dynamical family. We find S/2021 N1 is in a Kozai-Lidov…
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