Plutino

In astronomy, a plutino is a trans-Neptunian object that has a 2:3 orbital resonance with Neptune. They are named after Pluto, which also has this same orbital resonance¹.

Plutinos form the inner part of the Kuiper belt. About 1/4 of known Kuiper Belt objects (KBOs) are Plutinos.

Some of the largest plutinos:

Also considered to be similar to the plutinos are:

Pluto itself, but see paragraph below.
Charon, the largest of the 3 moons of Pluto
Nix, the middle moon of the 3 moons of Pluto
Hydra, the farthest of the 3 moons of Pluto

Apart from the Pluto system, the first plutino (1993 RO) was discovered on September 16, 1993.

¹The name of Plutino, if interpreted as a small Pluto is misleading. Instead, the name of Plutino simply characterises the orbit in 2:3 resonance. Pluto and its moons are consequently considered as Plutinos.

Orbits

Origin

It is believed that Pluto and a number of objects with similar semi-axes following originally non-resonant orbits have been captured by Neptune migrating outward.Preprint in arXiv

Current distribution

The diagram illustrates the orbits and relative sizes¹ of larger plutinos compared with the big three: Pluto, 90482 Orcus and 28978 Ixion marked by white circles. Pluto’s largest moon Charon is not shown to limit the cluttering of the diagram (diameter of 1207km, similar to that of Orcus).

The eccentricity of the orbits is represented by red segments (extending from perihelion to aphelion) and the inclination represented on Y axis. While majority of objects have low orbital inclination, a substantial number of them follow orbits similar to that of Pluto with inclination in 10-25^o range and eccentricities around 0.2-0.25, resulting in object's perihelion inside (or close to) the orbit of Neptune and aphelion close to the main Kuiper belt's outer edge (1:2 resonance). In addition to large objects, to illustrate the range of orbits’ parameters, three objects with extreme orbits are plotted (in yellow):

following the most highly inclined orbit (40^o)
with the most elliptical orbit (eccentricity=0.35), with the perihelion halfway between Uranus and Neptune and the aphelion well into the scattered disk region.
on a quasi-circular (eccentricity=0.04) orbit, lying almost perfectly on the ecliptic (inclination<0.5^o)

The distribution of all known plutinos (153 as of February, 2006) is plotted on the second diagram. Small inserts show histograms for orbit inclinations i (5^o interval) and eccentricity e (interval 0.05).

See also the comparison with the distribution of the classical objects.

¹For a few large objects with the diameters known with some precision, the current estimates are shown. For all others, the size of the object plotted is proportional to their absolute magnitude, assuming the albedo.

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. Numerical simulations suggest that Plutinos with the eccentricity 10%-30% smaller or bigger than that of Pluto are not stable in Gy timescales.Preprint in arXiv

External links

References

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: 3540260560 (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 (pdf)
Minor Planet Circular 2005-X77 Distant Minor planets was used for plutinos' orbits classification. The updated data can be found in MPC 2006-D28.

Trans-Neptunian objects

Gourt Home::Gourt :: Plutino