Neso (moon)

'''Neso
Discovery [1]
Discovered byM. Holman et al.
B. Gladman et al.
DiscoveredAugust 14, 2002
Mean Orbital elements [2]
Epoch June 10, 2003
Semi-major axis48.387 Gm
Eccentricity0.4945
Inclination132 *
Orbital period9374.0 d
(25.7 a)
Physical characteristics
Mean diameter60 km[2] **
Rotation period?
Albedo0.04 assumed[2]
Color?
Spectral type?

*to the ecliptic**based on the albedo


Neso (nee'-soe, IPA: /ˈniːsoʊ/; Greek Νησώ), 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.<ref name"IAU8213">IAU Circular 8213[3]
Enlarge picture
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.

Neso is about 60 km in diameter, and assuming the mean density of 1.5 g/cm3[4] its mass is estimated at 1.61017 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..[2]

Neso is named after one of the Nereides. Before the announcement of its name on February 3, 2007 (IAUC 8802), Neso was known by its provisional designation, S/2002 N 4.

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!

See also

References

1. ^ Discovery Circumstances from JPL
2. ^ 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. ^ M. Holman, JJ Kavelaars, B. Gladman, T. Grav, W. Fraser, D. Milisavljevic, P. Nicholson, J. Burns, V. Carruba, J.-M. Petit, P. Rousselot, O. Mousis, B. Marsden, R. Jacobson; Discovery of five irregular moons of Neptune, Nature, 430 (2004), pp. 865-867. Final preprint(pdf)
4. ^ Physical parameters from JPL

External links

Matthew J. Holman (* 1967) is a 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 planetary science in 1994.
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Brett J. Gladman, born April 19, 1966, is a Canadian astronomer and an Associate Professor at the University of British Columbia's Department of Physics and Astronomy, in Vancouver, British Columbia. He holds a Canada Research Chair in Planetary Astronomy.
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semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae.

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The metre or meter[1](symbol: m) is the fundamental unit of length in the International System of Units (SI).
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orbit's eccentricity, is an important parameter of the orbit that defines its absolute shape. Eccentricity may be interpreted as a measure of how much this shape deviates from a circle.
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Inclination in general is the angle between a reference plane and another plane or axis of direction.
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    irregular moon is a natural satellite following a distant, inclined, and often retrograde orbit. They are believed to have been captured by their parent planet, unlike regular satellites, which form in situ.
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    Brett J. Gladman, born April 19, 1966, is a Canadian astronomer and an Associate Professor at the University of British Columbia's Department of Physics and Astronomy, in Vancouver, British Columbia. He holds a Canada Research Chair in Planetary Astronomy.
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    Inclination in general is the angle between a reference plane and another plane or axis of direction.
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    orbit's eccentricity, is an important parameter of the orbit that defines its absolute shape. Eccentricity may be interpreted as a measure of how much this shape deviates from a circle.
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