Larissa

A confirmed moon in the Neptune system.

Named · Neptune VII · S/1989 N 2

Snapshot 2026-09-09 · catalog 1.0.0

Explore Larissa in Orrery

Physical measurements

Mean radius: 96 ± 7 kmmeasured · Source estimate; uncertainty is the source-reported standard error when available.
GM · gravitational parameter: 0.25484 ± 3.1223 km³ s⁻²measured · Source estimate; uncertainty is the source-reported standard error when available.
Mass: ≈ 3.8182e+18 ± 4.6781e+19 kgderived · GM/G; independent standard uncertainties combined in quadrature. No uncertainty is invented when the source omits GM uncertainty.
Mean density: ≈ 1.0303 ± 12.626 g cm⁻³derived · JPL derives density from GM and volume-equivalent radius.

PCK reference shape axes: ≈ 96 × ≈ 96 × ≈ 96 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.

NEP097 · Laplace plane · 2000-01-01.5 TDB

Semimajor axis: 73,500 km
Sidereal period: 0.554989 days
Eccentricity: 0.001
Inclination to reference plane: 0.2°
Argument of periapsis: 247.3°
Mean anomaly: 165.5°
Ascending node: 312°
Apsidal / nodal precession periods: 1.257 / 2.514 years
Reference-plane pole RA / Dec: 299.8 / 43.1°
Plane tilt to parent equator: 0.4°
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

NAIF-pck00011 supplies a modeled pole and prime meridian in the J2000 frame. A dated sky also needs compatible trajectories.

Pole right ascension: 299.36, 0, 0
Pole declination: 43.41, 0, 0
Prime meridian: 179.41, 649.053447, 0
Reference epoch: JD 2451545 TDB

Periodic corrections

RA and prime-meridian corrections multiply sine; declination corrections multiply cosine. Each row uses the same angle polynomial for its three corrections.

Term 1 · angle coefficients: 357.85, 52.316, 0RA: 0.7° · Dec: -0.51° · meridian: -0.48°
Term 2 · angle coefficients: 323.92, 62606.6, 0RA: 0° · Dec: 0° · meridian: 0°
Term 3 · angle coefficients: 220.51, 55064.2, 0RA: 0° · Dec: 0° · meridian: 0°
Term 4 · angle coefficients: 354.27, 46564.5, 0RA: 0° · Dec: 0° · meridian: 0°
Term 5 · angle coefficients: 75.31, 26109.4, 0RA: 0° · Dec: 0° · meridian: 0°
Term 6 · angle coefficients: 35.36, 14325.4, 0RA: -0.27° · Dec: -0.2° · meridian: 0.19°
Term 7 · angle coefficients: 142.61, 2824.6, 0RA: 0° · Dec: 0° · meridian: 0°
Term 8 · angle coefficients: 177.85, 52.316, 0RA: 0° · Dec: 0° · meridian: 0°
Term 9 · angle coefficients: 647.84, 125213.2, 0RA: 0° · Dec: 0° · meridian: 0°
Term 10 · angle coefficients: 355.7, 104.632, 0RA: 0° · Dec: 0° · meridian: 0°
Term 11 · angle coefficients: 533.55, 156.948, 0RA: 0° · Dec: 0° · meridian: 0°
Term 12 · angle coefficients: 711.4, 209.264, 0RA: 0° · Dec: 0° · meridian: 0°
Term 13 · angle coefficients: 889.25, 261.58, 0RA: 0° · Dec: 0° · meridian: 0°
Term 14 · angle coefficients: 1067.1, 313.896, 0RA: 0° · Dec: 0° · meridian: 0°
Term 15 · angle coefficients: 1244.95, 366.212, 0RA: 0° · Dec: 0° · meridian: 0°
Term 16 · angle coefficients: 1422.8, 418.528, 0RA: 0° · Dec: 0° · meridian: 0°
Term 17 · angle coefficients: 1600.65, 470.844, 0RA: 0° · Dec: 0° · meridian: 0°

Identity & availability

Stable catalog ID: larissa
JPL / NAIF satellite ID: 807
Names & designations: Larissa · S/1989 N 2
Discovery / rediscovery years: 1989Voyager Science Team

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.

Sources & evidence

JPL discovery circumstancestable tr[451] (zero-based); neptune / Larissa · References: IAU WGPSN
MPC satellite namesitems[90]; Neptune 7
JPL physical parameters#sat_phys_par; Neptune / Larissa / NAIF 807; mean radius · References: 1
JPL physical parameters#sat_phys_par; Neptune / Larissa / NAIF 807; GM · References: NEP097
NIST CODATA 2022Table of universal constants, Newtonian constant of gravitationVerified numeric transcription; see acquisition notes in the download.
JPL physical parameters#sat_phys_par; Neptune / Larissa / NAIF 807; density · References: *
JPL mean orbital elements#sat_elem row ID=444; Neptune / Larissa / NAIF 807 · References: 24
NAIF PCK 00011BODY807_POLE_RA/POLE_DEC/PM/NUT_PREC_*; BODY8_NUT_PREC_ANGLES; active data blocks
NAIF PCK 00011BODY807_RADII; active data block

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