S/2003 J 4

S/2003 J 4 is a natural satellite of Jupiter. It was discovered by a team of astronomers from the University of Hawaii led by Scott S. Sheppard in 2003.^[4][1]

S/2003 J 4

S/2003 J 4 imaged by the Canada-France-Hawaii Telescope during follow-up observations in February 2003
Discovery [1]
Discovered by	Scott S. Sheppard et al.
Discovery site	Mauna Kea Obs.
Discovery date	5 February 2003
Orbital characteristics [2]
Epoch 17 December 2020 (JD 2459200.5)
Observation arc	16.42 yr (5,997 d)
Earliest precovery date	10 December 2001
Semi-major axis	0.1473856 AU (22,048,570 km)
Eccentricity	0.4967418
Orbital period (sidereal)	–1.83 yr (–668.85 d)
Mean anomaly	146.33793°
Mean motion	0° 32m 17.664s / day
Inclination	149.40138° (to ecliptic)
Longitude of ascending node	249.91700°
Argument of perihelion	240.54004°
Satellite of	Jupiter
Group	Pasiphae group
Physical characteristics
Mean diameter	≈2 km[3]
Albedo	0.04 (assumed)[3]
Apparent magnitude	23.0[3]
Absolute magnitude (H)	16.7[2]

S/2003 J 4 is about 2 km in diameter, and orbits Jupiter at an average distance of 23,000,000 km in 669 days, at an inclination of 149° to the ecliptic, in a retrograde direction and with an eccentricity of 0.497.

It belongs to the Pasiphae group, irregular retrograde moons orbiting Jupiter at distances ranging between 22.8 and 24.1 Gm, and with inclinations ranging between 144.5° and 158.3°.

This moon was considered lost^[5][6][7][8] until late 2020, when it was recovered by amateur astronomers Kai Ly and Sam Deen in archival images from 2001-2018.^[9] The recovery of the moon was announced by the Minor Planet Center on 13 January 2021.^[2]