Neso , also known as Neptune XIII, is the outermost known natural satellite of

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

. It is a retrograde

irregular moon In astronomy, an irregular moon, irregular satellite or irregular natural satellite is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit. They have been captured by their parent planet, unlike regular sat ...

discovered by

Matthew J. Holman Matthew J. Holman (born 1967) is a Smithsonian Astrophysical Observatory, Smithsonian astrophysicist and lecturer at Harvard University. Holman studied at MIT, where he received his bachelor's degree in mathematics in 1989 and his PhD in planetar ...

Brett J. Gladman Brett James Gladman (born April 19, 1966) is a Canadian astronomer and a full professor at the University of British Columbia's Department of Physics and Astronomy in Vancouver, British Columbia. He holds the Canada Research Chair in planetary as ...

, ''et al.'' on August 14, 2002, though it went unnoticed until 2003. Neso orbits Neptune at a distance of more than 48 Gm (million km), making it (as of 2015) the most distant known moon of any planet. At apocenter, the satellite is more than 72 Gm from Neptune. This distance is great enough that it exceeds

Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

's aphelion, which is approximately 70 Gm from the Sun. TheIrregulars NEPTUNE GROUPS

Neso is also the moon with the longest orbital period, 26.67 years. It follows a retrograde, highly

inclined Incline, inclined, inclining, or inclination may refer to: *Grade (slope), the tilt, steepness, or angle from horizontal of a topographic feature (hillside, meadow, etc.) or constructed element (road, railway, field, etc.) *Slope, the tilt, steepn ...

, and highly

eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

orbit illustrated on the diagram in relation to other irregular satellites of Neptune. The satellites above the horizontal axis are prograde, the satellites beneath it are retrograde. The yellow segments extend from the pericentre to the apocentre, showing the eccentricity. Neso is about in diameter based on an assumed albedo, and assuming a mean density of 1.5 g/cm³, its mass is estimated at 2 kg. Given the similarity of the orbit's parameters with Psamathe (S/2003 N 1), it was suggested that both irregular satellites could have a common origin in the break-up of a larger moon. Neso is named after one of the Nereids. Before it was officially named on February 3, 2007 (IAUC 8802), Neso was known by its provisional designation, S/2002 N 4.

References

MPC: Natural Satellites Ephemeris Service
* Mean orbital parameter
from JPL

External links

{{DEFAULTSORT:Neso (Moon) Moons of Neptune Irregular satellites 20020814 Moons with a retrograde orbit

See also

References

External links