The plutinos (or plutiniens ) are objects transneptuniens, members of the Ceinture of Kuiper who are in resonance 2:3 with Neptune. That means that they carry out two Orbite S around the sun while Neptune makes three of them. So and even if they cross the orbit of giant planet, they cannot be ejected gravitationally by this one.
This characteristic being divided by Pluto, these bodies were named “plutinos” (i.e. “small let us plutons”).
Some representatives of this family:
- : it crosses the orbit of Neptune without never approaching planet. This characteristic is shared by a certain number of other family members of the plutinos;
- : like the pair Pluto Charon, it is about a binary object;
- (90482) Orcus considered currently largest if one excludes Pluton and his larger moon Charon;
- (28978) Ixion (759 km diameter) held during a few months the record of size of the planetoids.
Orbits
The diagram shows the orbits and relative dimensions of large the plutinos (more precisely, for the majority, the Magnitudes) compared with those of three the largest: Pluto, (90482) Orcus and (28978) Ixion (marked by the white circles).The largest satellite of Pluto Charon is not shown to avoid encumbering the diagram (its diameter of 1207 km is similar to that of Orcus). The eccentricity of the orbits is represented by the red segments (Périhélie with the Aphélie) with the Inclinaison represented on the vertical axis.
If, in majority, of the orbits are not very tilted, of the many orbits of the plutinos are similar to that of Pluto with the slope between 10-25° and the eccentricity of 0,2-0,25, which gives a perihelion inside (or close) of the orbit of Neptune and the aphelion close to the limit external of the principal part of the Ceinture of Kuiper (with resonance 1:2). To illustrate the fork of the parameters of the orbits, three objects with the extreme orbits were shown in (yellow):
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on the most tilted orbit (40°);
- on the most eccentric orbit (eccentricity = 0,35), its perihelion halfway between Uranus and Neptune and its aphelion in the area occupied by the scattered objects;
- on an almost circular orbit (eccentricity = 0,04) and almost coplanar with the ecliptic (inclination < 0,5°).
The second diagram shows all the plutinos (153 in February 2006). The Histogramme S present the distribution of the slope I (interval 5o) and of the eccentricity E (interval 0,05) of the orbits.
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