Plutino

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, the largest and the first plutino discovered. The name refers only to the orbital resonance and does not imply common physical characteristics.

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, the first plutino, (385185) 1993 RO, was discovered on September 16, 1993.

Orbits

Origin

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 the strongest and most stable among all resonances. This is the main reason it contains the largest number of bodies.

(15810) 1994 JR1

(15810) 1994 JR₁, also written (15810) 1994 JR1, is a minor planet that orbits around the Sun in an orbit entirely located beyond Neptune. It is the first object that was confirmed to be a quasi-satellite of Pluto.

Discovery, orbit and physical properties

(15810) 1994 JR₁ was discovered on May 12, 1994, by M. J. Irwin and A. Zytkow with the 2.5 m Isaac Newton Telescope at the Roque de los Muchachos Observatory in the island of La Palma. It is a plutino, so it is trapped in a 2:3 mean motion resonance with Neptune, similarly to dwarf planet Pluto (the largest known plutino). It has a perihelion (closest approach to the Sun) of 34.753 AU and an aphelion (farthest distance from the Sun) of 43.722 AU, so it is moving in a relatively eccentric orbit entirely beyond Neptune. It is about 127 km in diameter.

Quasi-satellite dynamical state and orbital evolution

(15810) 1994 JR₁ is currently following a quasi-satellite loop around Pluto. In contrast with the cases of 2002 VE68 or (309239) 2007 RW10, the quasi-satellite state of (15810) 1994 JR₁ is mainly the result of resonances with Neptune not caused by a discrete close encounter with another body. This dynamical behavior is recurrent: the object becomes a Plutonian quasi-satellite every 2 Myr and remains in that phase for nearly 350,000 years.