 | |
| Discovery[1][2] | |
|---|---|
| Discovered by | Scott S. Sheppard |
| Discovery site | Cerro Tololo Obs. |
| Discovery date | 11 May 2018 |
| Designations | |
| S/2018 J 4 | |
| Orbital characteristics[3] | |
| Epoch 1 January 2000 (JD 2451545.0) | |
| Observation arc | 6 years 2024-12-03 (last obs)[4] |
| Earliestprecovery date | 2018-05-11 |
| Satellite of | Jupiter |
| Group | Carpo |
| Proper orbital elements | |
Propersemi-major axis | 16,328,500 km (0.109149 AU) |
Propereccentricity | 0.177 |
Properinclination | 50.2° (toecliptic) |
Properorbital period | 1.17 years (426.26 d) |
Precession ofperihelion | N/A arcsec / yr |
Precession of theascending node | 6638.868 arcsec / yr |
| Physical characteristics | |
| ≈2 km[5] | |
| Albedo | 0.04(assumed)[5] |
| 23.5[5] | |
| 16.75 (28 obs)[4][1] | |
S/2018 J 4 is a small outernatural satellite of Jupiter discovered byScott S. Sheppard on 11 May 2018, using the 4.0-meterVíctor M. Blanco Telescope atCerro Tololo Observatory,Chile. It was announced by theMinor Planet Center on 20 January 2023, after observations were collected over a long enough time span to confirm the satellite's orbit.[1] The satellite has a diameter of about 2 km (1.2 mi) for anabsolute magnitude of 16.7.[5]
S/2018 J 4 is anirregular moon of Jupiter on an highlyinclinedprograde orbit at an angle of 53° with respect to theecliptic plane. It belongs to the same group as the similarly-inclined moonCarpo, which was long thought to be an outlier until the discovery of S/2018 J 4.[5] Like all irregular moons of Jupiter, S/2018 J 4's orbit is highly variable over time due to gravitationalperturbations by the Sun and other planets.[6] On average, S/2018 J 4's orbit has asemi-major axis of 16.3 million km (10.1 million mi), aneccentricity of 0.18, and a very highinclination of 50° with respect to theecliptic.[3]
Like Carpo, S/2018 J 4's very high inclination subjects it to theLidov–Kozai resonance, where there is a periodic exchange between its orbital eccentricity and inclination while itsargument of pericenter oscillates about a constant value withoutapsidally precessing.[7] For example, the Lidov–Kozai resonance causes Carpo's eccentricity and inclination to fluctuate between 0.19–0.69 and 44–59°, respectively.[6] S/2018 J 4's argument of pericenter oscillates about 270° with respect to the ecliptic, which keeps its perijove always above Jupiter and apojove below Jupiter.[3]
Listed in increasing approximate distance from Jupiter | |
| Inner moons | |
| Galilean moons | |
| Themisto | |
| Himalia group (9) | |
| Carpo group (2) | |
| Valetudo | |
| Ananke group (27) | |
| Carme group (31) | |
| Pasiphae group (18) | |
| See also | |
