In 2006, accurate measurements of the orbit from the Keck Laser guide star adaptive optics system were reported.

Observation data put the orbital distance at the time of 664.6 km (with an unstated uncertainty), and give a size for the slightly larger component, which retains the name Patroclus with overall volume equivalent to a 113±3 km–diameter sphere, with the smaller component now named Menoetius with a volume equivalent to a 104±3 km–diameter sphere.

Analysis of the best rated lightcurves gave a rotation period between 102.8 and 103.5 hours with a brightness amplitude of less than 0.1 magnitude (U=2/3/).

[11][13] The Collaborative Asteroid Lightcurve Link adopts the results obtained by IRAS, that is, an albedo of 0.0471 and a diameter of 140.92 kilometers based on an absolute magnitude of 8.19.

[5] Because the density of the components (0.88 g/cm3) is less than water and about one third that of rock, it was suggested that the Patroclus system, previously thought to be a pair of rocky asteroids, is more similar to a comet in composition.

[24] It is suspected that many Jupiter trojans are in fact small planetesimals captured in the Lagrange point of the Jupiter–Sun system during the migration of the giant planets 3.9 billion years ago.

[27] The Patroclus–Menoetius system is a scheduled target for Lucy, a flyby mission to multiple asteroids, mostly Jupiter trojans.

However, Alexander Pope shifted the stress to the first 'o', /pəˈtroʊkləs/, a convention from Latin poetry,[b] for metrical convenience in his verse translation of Homer, and this irregular pronunciation has become established in English.