astronomy

S/2023 U 1

S/2023 U 1 is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand S/2023 U 1 rather than just read about it. In short: S/2023 U 1 is a small and distant irregular moon of Uranus, with a diameter of around 8–12 km (5–7 mi). It was discovered on 4 November 2023 by Scott S.

Key takeaways

S/2023 U 1 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect S/2023 U 1 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of S/2023 U 1 from memory before moving on to harder problems.

Reference excerpt

S/2023 U 1 is a small and distant irregular moon of Uranus, with a diameter of around 8–12 km (5–7 mi). It was discovered on 4 November 2023 by Scott S. Sheppard using the 6.5-meter Magellan–Baade Telescope at Las Campanas Observatory, Chile, and later announced on 23 February 2024. It orbits Uranus in the retrograde direction at an average distance of about 8 million km (5 million mi) and takes almost two Earth years to complete one orbit.

Discovery S/2023 U 1 was discovered on 4 November 2023 by Scott S. Sheppard during his search for Uranian irregular moons with the 6.5-m Magellan–Baade Telescope at Las Campanas Observatory, Chile. Sheppard was able to detect this faint moon through the shift-and-add technique, in which he took many long-exposure telescope images, aligned and shifted them to follow Uranus's motion, and then added them together to create a single deep image that would show Uranian moons as points of light against trailed background stars and galaxies. Applying the shift-and-add technique to very large aperture telescopes like Magellan enabled Sheppard to probe deeper than previous Uranian irregular moon surveys. To plan follow-up observations of S/2023 U 1, Sheppard collaborated with Marina Brozović and Robert Jacobson to calculate predictions for the moon's orbit and positions on other dates. Sheppard observed S/2023 U 1 with the Magellan Telescope on 6 and 13 December 2023, and was able to trace the moon back to his earlier observations on 8 September and 2 December 2021. S/2023 U 1 was confirmed and announced by the Minor Planet Center on 23 February 2024, bringing Uranus's number of known moons from 27 to 28. It is the first Uranian moon discovered in over 20 years since the discovery of Margaret in 2003.

Orbit

S/2023 U 1 is an irregular moon of Uranus, since it has a distant and highly elliptical and inclined orbit. Irregular moons are loosely bound by Uranus's gravity because of their great distance from the planet, so their orbits are frequently perturbed by the gravity of the Sun and other planets. This results in significant changes in the orbits of irregular moons over short periods of time, so a simple Keplerian elliptical orbit cannot accurately describe the long-term orbital motions of irregular moons. Instead, proper or mean orbital elements are used to describe the long-term orbits of irregular moons more accurately, since these are calculated by averaging out the perturbed orbit over a long period of time. Over an 800-year time span from 1600 to 2400, S/2023 U 1's average semi-major axis or orbital distance from Uranus is 7.98 million km (4.96 million mi; 0.0533 AU), with an average orbital period of 1.86 years (681 d). S/2023 U 1 has an average orbital eccentricity of 0.25 and an average inclination of 144° with respect to the ecliptic, or the plane of Earth's orbit. Since S/2023 U 1's orbital inclination is greater than 90°, the moon has a retrograde orbit, meaning it orbits in the opposite direction of Uranus' orbit around the Sun. Due to perturbations, S/2023 U 1's orbital elements fluctuate over time: its semi-major axis can range from 7.97 to 7.98 million km (4.95 to 4.96 million mi), eccentricity from 0.14 to 0.29, and inclination from 141° to 144°. S/2023 U 1's orbit exhibits nodal precession with an average period of about 5,000 Earth years and apsidal precession with an average period of about 5,100 Earth years. S/2023 U 1 is part of the Caliban group, a cluster of retrograde irregular moons of Uranus that includes Stephano and the group's namesake Caliban. The moons of the Caliban group have orbital elements that are clustered with semi-major axes between 7–8 million km (4.3–5.0 million mi), eccentricities between 0.16 and 0.23, and inclinations between 141° and 144°. Like all other irregular moon groups, the Caliban group is thought to have formed from the destruction of a larger captured moon of Uranus due to asteroid and comet impacts, which left many fragments in similar orbits around Uranus.

Physical characteristics S/2023 U 1 is extremely faint with an average apparent magnitude of 26.7, so it could only be observed with long-exposure imaging by large-aperture telescopes like the Magellan Telescope. Nothing is known about S/2023 U 1's physical properties other than its absolute magnitude of 13.7, which can be used to estimate the moon's diameter. Assuming a geometric albedo range of 0.04–0.10 that is typical for most irregular moons, S/2023 U 1 has a diameter between 8–12 km (5–7 mi), with Sheppard estimating the diameter to be 8 km (5.0 mi). S/2023 U 1 is tied with Uranus XXVIII as the smallest known moon of Uranus as of 2025.

Notes

References

External links Sheppard, Scott S. (23 February 2024). "New Uranus and Neptune Moon Images". Earth & Planetary Laboratory. Carnegie Institution for Science.

Illustrations

Worked examples

Example 1 — a first encounter with S/2023 U 1

Start with the simplest possible case. Write down what S/2023 U 1 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to S/2023 U 1 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about S/2023 U 1 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of S/2023 U 1

In research: S/2023 U 1 appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses S/2023 U 1 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: S/2023 U 1 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 2023, Caliban group, Discoveries by Scott S. Sheppard, so understanding it makes those chapters shorter.
In everyday life: Look for S/2023 U 1 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study S/2023 U 1 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what S/2023 U 1 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain S/2023 U 1 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is S/2023 U 1 in simple terms?

S/2023 U 1 is a small and distant irregular moon of Uranus, with a diameter of around 8–12 km (5–7 mi). It was discovered on 4 November 2023 by Scott S.

Why does S/2023 U 1 matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study S/2023 U 1?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on S/2023 U 1.