Plutino

The motion of Orcus and Pluto in a rotating frame with a period equal to Neptune's orbital period. (Neptune is held stationary.)

The largest plutinos compared in size, albedo and colour.

In astronomy, a plutino is a trans-Neptunian object in 2:3 mean motion resonance with Neptune. For every 2 orbits that a Plutino makes, Neptune orbits 3 times. Plutinos are named after Pluto, which follows an orbit trapped in the same resonance, with the Italian diminutive suffix -ino. The name refers only to the orbital resonance and does not imply common physical characteristics; it was invented to describe those bodies smaller than Pluto (hence the diminutive) following similar orbits. The class includes Pluto itself and its moons.

Plutinos form the inner part of the Kuiper belt and represent about a quarter of the known Kuiper Belt objects (KBOs). Plutinos are the largest class of the resonant trans-Neptunian objects (i.e. bodies in orbital resonances with Neptune).

Aside from Pluto itself and Charon, the first plutino, 1993 RO, was discovered on September 16, 1993.

The largest plutinos include Pluto, 90482 Orcus, 28978 Ixion, (84922) 2003 VS2, 38628 Huya, and (208996) 2003 AZ84.

Orbits

Origin

It is thought that objects that are currently in mean orbital resonances with Neptune initially followed independent heliocentric paths. During Neptune’s migration (see origins of the Kuiper belt), the objects have been caught into the resonances sweeping outward.^[1]

Orbital characteristics

Orbits and sizes of the larger plutinos. The eccentricity of the orbits is represented by the segments extending from perihelion to aphelion and the inclination is represented on the vertical axis.

The distribution of plutinos. Small inserts show histograms for the distribution of orbital inclinations and eccentricity.

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 x 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.
• 2007 JH₄₃ following a quasi-circular orbit
• 2002 VX₁₃₀ lying almost perfectly on the ecliptic (inclination less than 1.5°)

For reference, also shown is (119951) 2002 KX₁₄, though it is not a plutino.

See also the comparison with the distribution of the cubewanos.

Long-term stability

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.^[2] Numerical simulations suggest that plutinos with the eccentricity 10%-30% smaller or bigger than that of Pluto are not stable in Ga timescales.^[3]

References

1. ^ Malhotra The Origin of Pluto's Orbit: Implications for the Solar System Beyond Neptune Astronomical Journal, 110 (1995), p420. Preprint in arXiv
2. ^ Wan, X.-S; Huang, T.-Y. (2001). "The orbit evolution of 32 plutinos over 100 million year". Astronomy and Astrophysics 368: 700–705. doi:10.1051/0004-6361:20010056. http://adsabs.harvard.edu/abs/2001A&A...368..700W. Retrieved 2008-02-21. 
3. ^ Qingjuan Yu and Scott Tremaine The Dynamics of Plutinos The Astronomical Journal, 118 (1999), pp. 1873–1881 Preprint in arXiv

• D.Jewitt, A.Delsanti The Solar System Beyond The Planets in Solar System Update : Topical and Timely Reviews in Solar System Sciences , Springer-Praxis Ed., ISBN 3-540-26056-0 (2006). Preprint of the article (pdf)
• Bernstein G.M., Trilling D.E., Allen R.L. , Brown K.E , Holman M., Malhotra R. The size Distribution of transneptunian bodies. The Astronomical Journal, 128, 1364-1390. preprint on arXiv
• 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.

External links

• David Jewitt (Univ. of Hawaii) on Plutinos
• Minor Planet Center, List of TNOs
• MPC List of Distant Minor Planets

Astronomy portal

v • d • e The Solar System The Sun · Mercury · Venus · Earth · Mars · Ceres · Jupiter · Saturn · Uranus · Neptune · Pluto · Haumea · Makemake · Eris Moons (Terrestrial · Martian · Jovian · Saturnian · Uranian · Neptunian · Plutonian · Haumean · Eridian) · Rings (Jovian · Saturnian · Uranian · Neptunian) Meteoroids · Minor planets (Asteroids (Main belt) · Centaurs · TNOs (Kuiper belt · Scattered disc) ) · Comets (Hills cloud · Oort cloud) Related articles: astronomical object, star, planet, dwarf planet, small body and planetary system See also the Solar System's list of objects, sorted by size, the list of minor planets, or the Solar System Portal