Neso, also known as Neptune XIII, is the outermost irregular natural satellite of Neptune. It was discovered by Matthew J. Holman, Brett J. Gladman, et al. on August 14, 2002, though it went unnoticed until 2003.^[3][4] Matthew J. Holman is a Smithsonian Astrophysicist and lecturer at Harvard University. ... Brett J. Gladman is a Canadian astronomer and an Associate Professor at the University of British Columbias Department of Physics and Astronomy, in Vancouver, British Columbia. ... August 14 is the 226th day of the year in the Gregorian Calendar (227th in leap years), with 139 days remaining. ... For album titles with the same name, see 2002 (album). ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae. ... A gigametre (American spelling: gigameter) (symbol: Gm) is a unit of length equal to 109 metres. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... Inclination in general is the angle between a reference plane and another plane or axis of direction. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... In astronomy, a Julian year is a unit of time defined as exactly 365. ... In geometry, a diameter (Greek words diairo = divide and metro = measure) of a circle is any straight line segment that passes through the center and whose endpoints are on the circular boundary, or, in more modern usage, the length of such a line segment. ... On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ... Albedo is a ratio of scattered to incident electromagnetic radiation power. ... In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. ... Asteroids are assigned a type based on spectral shape, color, and sometimes albedo. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... Matthew J. Holman is a Smithsonian Astrophysicist and lecturer at Harvard University. ... Brett J. Gladman is a Canadian astronomer and an Associate Professor at the University of British Columbias Department of Physics and Astronomy, in Vancouver, British Columbia. ... August 14 is the 226th day of the year in the Gregorian Calendar (227th in leap years), with 139 days remaining. ... For album titles with the same name, see 2002 (album). ... 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ...

Irregular satellites of Neptune.

Neso orbits Neptune at a distance of more than 48 Gm (million km), making it the most distant known moon of any planet¹. It follows a highly inclined and highly eccentric 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. giga- (symbol: G) is a prefix in the SI system of units denoting 109, or 1 000 000 000. ... km redirects here. ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ... (This page refers to eccitricity in astrodynamics. ... Prograde motion is the motion of a planetary body in a direction similar to that of other bodies within its system, and is sometimes called direct motion, especially in astrology. ... A diagram of Keplerian orbital elements. ... A diagram of Keplerian orbital elements. ...

Neso is about 60 km in diameter, and assuming the mean density of 1.5 g/cm^3[5] its mass is estimated at 1.6 x 10¹⁷kg. KG, Kg or kg may indicate: A Kampfgeschwader, a bomber squadron of the former German Luftwaffe Basketball Player Kevin Garnett An abbreviation for kilogram (always kg) Knight of the Garter, a British decoration Kommanditgesellschaft, German version of a limited partnership Kongo language (ISO 639 alpha-2) An abbreviation for konig...

Given the similarity of the orbit's parameters with Psamathe (S/2003 N1), it was suggested that both irregular satellites could have a common origin in the break-up of a larger moon..^[2] Psamathe (sam-a-thee, Greek Ψαμαθεια, Latin Psamathē) is an irregular natural satellite of Neptune. ...

Neso is named after one of the Nereides. Prior to January 29, 2007, Neso was known by its provisional designation, S/ 2002 N 4. January 29 is the 29th day of the year in the Gregorian calendar. ... This article or section does not cite its references or sources. ...

¹Such distances are of the order of magnitude of heliocentric distances of inner planets rather than moons; at apocenter the satellite is more than 72 Gm (72 million km) from the planet to compare with Mercury's aphelion of ~70 Gm! Heliocentric Solar System Heliocentrism (lower panel) in comparsion to the geocentric model (upper panel) In astronomy, heliocentrism is the belief that the Sun is at the center of the Universe and/or the Solar System. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ...

See also

• irregular satellites

In astronomy, an irregular satellite is a natural satellite following a distant, inclined, often retrograde orbit and believed to be captured as opposed to a regular satellite, formed in situ. ...

External links

• Matthew Holman's Neptune's page
• David Jewitt's pages
• Scott Sheppard's pages

References

1. ^ Discovery Circumstances from JPL
2. ^ ^{a b c d} S. Sheppard, D.Jewitt and J.Kleyna A Survey for "Normal" Irregular Satellites Around Neptune: Limits to Completeness, The Astronomical Journal, 132 (2006), pp. 171–176. Preprint.
3. ^ IAU Circular 8213
4. ^ M. Holman, JJ Kavelaars, B. Gladman, Grav, Tommy; Gladman, Brett J; Fraser, Wesley C; Milisavljevic, Dan; Nicholson, Philip D; Burns, Joseph A; Carruba, Valerio; Petit, Jean-Marc; Rousselot, Philippe; Mousis, Oliver; Marsden, Brian G; Jacobson, Robert A Discovery of five irregular moons of Neptune, Nature, 430 (2004), pp. 865-867. Final preprint(pdf)
5. ^ Physical parameters from JPL

• Ephemeris from IAU
• Mean orbital parameters from JPL