In astronomy, the plutinos are a dynamical group of trans-Neptunian objects that orbit in 2:3 mean-motion resonance with Neptune. This means that for every two orbits a plutino makes, Neptune orbits three times. The dwarf planet Pluto is the largest member and namesake of this group. Plutinos are named after mythological creatures associated with the underworld.
Plutinos form the inner part of the Kuiper belt and represent about a quarter of the known Kuiper belt objects. They are the largest class of the resonant trans-Neptunian objects (also see adjunct box with hierarchical listing). Aside from Pluto itself, the first plutino, (385185) 1993 RO, was discovered on September 16, 1993.
It is thought that objects that are currently in mean orbital resonances with Neptune initially followed independent heliocentric paths. As Neptune migrated outward early in the Solar System's history (see origins of the Kuiper belt), the bodies it approached would have been scattered; during this process, some of them would have been captured into resonances. The 3:2 resonance is a low-order resonance and the strongest and most stable among all resonances. This is the main reason it contains the largest number of bodies. The cloud of low-inclination bodies beyond 40 AU is the cubewano family, while bodies with higher eccentricities (0.05 to 0.34) and semimajor axes close to the 3:2 Neptune resonance are plutinos.
While the majority of plutinos have low orbital inclinations, a substantial number of them follow orbits similar to that of Pluto, with inclinations in the 10–25° range and eccentricities around 0.2–0.25, resulting in perihelia inside (or close to) the orbit of Neptune and aphelia close to the main Kuiper belt's outer edge (where objects have 1:2 resonance with Neptune).
The orbital periods of plutinos cluster around 247.3 years (1.5 × Neptune's orbital period), varying by at most a few years from this value.
Unusual plutinos include:
- 2005 TV189, which follows the most highly inclined orbit (34.5°)
- (15875) 1996 TP66, which has the most elliptical orbit (its eccentricity is 0.33), with the perihelion halfway between Uranus and Neptune
- (470308) 2007 JH43 following a quasi-circular orbit
- 2002 VX130 lying almost perfectly on the ecliptic (inclination less than 1.5°)
See also the comparison with the distribution of the cubewanos.
The gravitational influence of Pluto is usually neglected given its small mass. However, the resonance width (the range of semi-axes compatible with the resonance) is very narrow and only a few times larger than Pluto's Hill sphere (gravitational influence). Consequently, depending on the original eccentricity, some plutinos will be driven out of the resonance by interactions with Pluto. Numerical simulations suggest that the orbits of plutinos with an eccentricity 10%–30% smaller or larger than that of Pluto are not stable over Ga timescales.
The distribution of plutinos (and the reference non-plutino 2002 KX14). Small inserts show histograms for the distributions of orbital inclination and eccentricity.
The plutinos brighter than HV=6 include:
|134340 Pluto||39.3||29.7||17.1||−0.7||2322||130||0.49–0.66||1930||Clyde Tombaugh||JPL|
|90482 Orcus||39.2||30.3||20.6||2.31±0.03||917±25||6.32±0.05||0.28±0.06||0.37||2004||M. Brown,
|(208996) 2003 AZ84||39.4||32.3||13.6||3.74±0.08||727.0+61.9
|≈ 3||0.141±0.011||0.61||2001||Deep Ecliptic Survey||JPL|
|2017 OF69||39.5||31.3||13.6||4.091±0.12||≈ 380–680||?||?||?||2017||D. J. Tholen,
S. S. Sheppard,
|(84922) 2003 VS2||39.3||36.4||14.8||4.1±0.38||523.0+35.1
|(455502) 2003 UZ413||39.2||30.4||12.0||4.38±0.05||≈ 600||≈ 2||?||0.46±0.06||2001||M. Brown,
|(175113) 2004 PF115||39.0||36.5||13.4||4.54±0.25||406.3+97.6
|(144897) 2004 UX10||39.2||37.4||9.5||4.75±0.16||361.2+124.2
|> ≈ 0.3||0.172+0.141
|2014 JR80||39.5||36.0||15.4||4.9||≈ 240–670||?||?||?||2014||Pan-STARRS||JPL|
|2014 JP80||39.5||36.7||19.4||4.9||≈ 240–670||?||?||?||2014||Pan-STARRS||JPL|
|38628 Huya||39.4||28.5||15.5||5.04±0.03||406±16||≈ 0.5||0.083±0.004||0.57±0.09||2000||Ignacio Ferrin||JPL|
|(469987) 2006 HJ123||39.3||27.4||12.0||5.32±0.66||283.1+142.3
|2006||Marc W. Buie||JPL|
|(469372) 2001 QF298||39.3||34.9||22.4||5.43±0.07||408.2+40.2
|0.39±0.06||2001||Marc W. Buie||JPL|
|0.70±0.03||1999||E. P. Rubenstein,
|(307463) 2002 VU130||39.3||31.2||14.0||5.47±0.83||252.9+33.6
|2002||Marc W. Buie||JPL|
|(84719) 2002 VR128||39.3||28.9||14.0||5.58±0.37||448.5+42.1
|(55638) 2002 VE95||39.4||30.4||16.3||5.70±0.06||249.8+13.5
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- Minor Planet Center Orbit database (MPCORB) as of 2008-10-05.
- Minor Planet Circular 2008-S05 (October 2008) Distant Minor planets was used for orbit classification.