S/2018 J 3

{{Short description|Outer moon of Jupiter}}

{{Infobox planet

| name = S/2018 J 3

| image =

| image_size =

| caption =

| discovery_ref =

| discoverer = Scott S. Sheppard

| discovery_site = Las Campanas Obs.

| discovered = 12 May 2018

| orbit_ref =

| epoch = 25 February 2023 (JD 2460000.5)

| observation_arc = 4.35 yr (1590 d)

| earliest_precovery_date =

| semimajor = {{cvt|0.1525861|AU|km|lk=in}}

| eccentricity = 0.2731285

| period = –1.93 yr (–704.56 days)

| mean_anomaly = 16.59790°

| mean_motion = {{Deg2DMS|0.51095907|sup=ms}} / day

| inclination = 164.90043° {{small|(to ecliptic)}}

| asc_node = 240.00514°

| arg_peri = 296.52870°

| satellite_of = Jupiter

| group = Carme group

| mean_diameter = ≈{{val|1|u=km}}

| rotation =

| albedo =

| magnitude = 23.9

| abs_magnitude = 17.3

}}

S/2018 J 3 is a small outer natural satellite of Jupiter discovered by Scott S. Sheppard on 12 May 2018, using the 6.5-meter Magellan-Baade Telescope at Las Campanas Observatory, Chile. It was announced by the Minor Planet Center on 19 January 2023, after observations were collected over a long enough time span to confirm the satellite's orbit.

S/2018 J 3 is part of the Carme group, a tight cluster of retrograde irregular moons of Jupiter that follow similar orbits to Carme at semi-major axes between {{convert|22–24|e6km|e6mi|abbr=unit}}, orbital eccentricities between 0.2–0.3, and inclinations between 163–166°. It has a diameter of about {{cvt|1|km|mi}} for an absolute magnitude of 17.3, making it one of Jupiter's smallest known moons.