Atlas of Worlds

Nereid

A confirmed moon in the Neptune system.

Named · Neptune II

Snapshot 2026-09-09 · catalog 1.0.0

Explore Nereid in Orrery

Physical measurements

Mean radius
170 ± 25 kmmeasured · Source estimate; uncertainty is the source-reported standard error when available.
GM · gravitational parameter
— JPL’s NEP101 summary gives 0.00000 ± 0.00000: a placeholder, not a physical zero mass.
Mass
— Mass requires an admitted GM estimate.
Mean density
— Source reports no value.

PCK reference shape axes: ≈ 170 × ≈ 170 × ≈ 170 km. These are model axes, not a mapped surface.

Orbit descriptions

Mean elements describe an average orbit. They are not positions for a chosen date.

NEP105 · ecliptic plane · 2020-01-01.0 TDB
Semimajor axis
5,513,900 km
Sidereal period
360.133 days
Eccentricity
0.751
Inclination to reference plane
5.1°
Argument of periapsis
296.8°
Mean anomaly
318.5°
Ascending node
319.5°
Apsidal / nodal precession periods
7,990.43 / 9,426.33 years
Reference-plane pole RA / Dec
— / —°
Plane tilt to parent equator
—°
Reference center
Not specified in this summary sourceThe summary table identifies a parent system but does not explicitly specify the reference center for each solution. Do not infer a physical-primary center, especially for Pluto’s circumbinary moons.

Orientation

No supported orientation model in the admitted PCK source.

Identity & availability

Stable catalog ID
nereid
JPL / NAIF satellite ID
802
Names & designations
Nereid
Discovery / rediscovery years
1949G.P. Kuiper

No validated dated trajectory admitted in catalog 1.0.0. Mean elements are not ephemerides.

No image or global texture admitted in this catalog release.No environment measurements admitted in this catalog release.

Nereid’s zero GM source placeholder is withheld from physical calculations.

Sources & evidence

  1. JPL discovery circumstancestable tr[446] (zero-based); neptune / Nereid · References: IAU WGPSN
  2. MPC planetary satellite listitems[9]; Neptune 2
  3. MPC satellite namesitems[105]; Neptune 2
  4. JPL physical parameters#sat_phys_par; Neptune / Nereid / NAIF 802; mean radius · References: 1
  5. JPL physical parameters#sat_phys_par; Neptune / Nereid / NAIF 802; GM · References: NEP101
  6. JPL physical parameters#sat_phys_par; Neptune / Nereid / NAIF 802; density · References: n/a
  7. JPL mean orbital elements#sat_elem row ID=447; Neptune / Nereid / NAIF 802 · References: 44
  8. NAIF PCK 00011BODY802_RADII; active data block

Full catalog, uncertainty and source manifests · All Neptune moons · Moon model limits