Eupheme (moon)
A small, lost-and-found retrograde moon of Jupiter.
Eupheme, also known as Jupiter LX and originally designated S/2003 J 3, is a small outer moon of Jupiter, measuring just 2 km across. It orbits the planet at an average distance of 20 million km, with its farthest point reaching 27.7 million km.
A team from the University of Hawaiʻi, led by Scott S. Sheppard, first spotted the moon in 2003, but it was subsequently lost. It was rediscovered in 2017 and officially designated that year. The moon received its permanent name in 2019, chosen after a naming contest on Twitter hosted by the Carnegie Institute. The name Eupheme comes from the ancient Greek spirit of good omens, praise, and applause, daughter of Hephaestus and Aglaea and granddaughter of Zeus. The name ends with an "e" to indicate its retrograde orbit.
Eupheme takes about 588 days to circle Jupiter, following a retrograde path with an inclination of 148° to the ecliptic and an orbital eccentricity of 0.370. It belongs to the Ananke group, a collection of retrograde irregular moons orbiting between 19.3 and 22.7 million km from Jupiter at inclinations near 150°. The moon reached its farthest point from Jupiter, or apojove, on 23 January 2026, at a distance of 0.185 AU (27.7 million km).
Quick Facts
- Pronounced
- juː · ˈ · f · iː · m · iː
- Adjective
- Euphemean juː · f · ᵻ · ˈ · m · iː · ə · n
- Named After
- Ευφήμη Eyphēmē
- Discoverer
- Scott S. Sheppard
- Discovered
- 2003
- Mpc Name
- Jupiter LX
- Epoch
- 2026-01-01
- Observation Arc
- 2003 · 2024 / 2024-12-03 (last obs)
- Periapsis
- 12.7 million km
- Apoapsis
- 27.7 million km / (2026-Jan-23)
- Semimajor
- 20.2 million km
- Inclination
- 148.0°
Facts from the source article.
Lore & Background
Eupheme was discovered in 2003 by a team of astronomers from the University of Hawaiʻi led by Scott S. Sheppard. Following its discovery, the moon was lost until it was recovered in 2017, when it received its permanent designation. It was named in 2019 after Eupheme, the ancient Greek spirit of words of good omen, praise, acclaims, shouts of triumph, and applause, daughter of Hephaestus and Aglaea and granddaughter of Zeus. The name was suggested by Twitter user Lunartic (@iamalunartic) in a naming contest held by the Carnegie Institute on the social network, who concurrently helped in naming another Jovian moon, Philophrosyne. The name ends in an 'e' because the orbit is retrograde.
Reader's Guide
Eupheme belongs to the Ananke group, a set of retrograde irregular moons that orbit Jupiter between 19.3 and 22.7 million km at inclinations of roughly 150°. Its orbit is retrograde, with an average distance of 20 million km, an inclination of 148° to the ecliptic, and an eccentricity of 0.370. It takes 588 days to complete one orbit. Eupheme came to apojove (its farthest distance from Jupiter) on 23 January 2026, when it was 27.7 million km (0.185 AU) from Jupiter. The moon's recovery in 2017 after being lost for 14 years highlights the challenges of tracking small, distant irregular satellites. Its naming via a social media contest reflects a modern approach to engaging the public in astronomical nomenclature.
Did You Know?
- Eupheme is also known as Jupiter LX and was originally designated S/2003 J 3.
- It was discovered in 2003 by a team led by Scott S. Sheppard from the University of Hawaiʻi.
- The moon was lost after its discovery and recovered in 2017.
More in Moons of Jupiter 1-24
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