the preparations for the Pluto flyby. Dynamics and origin The orbits of Neptune trojans are highly stable; Neptune may have retained up to 50% of the original post-migration trojan population over the age of the Solar System. Neptune's can host stable trojans equally well as its . Neptune trojans can librate up to 30° from their associated Lagrangian points with a 10,000-year period. Neptune trojans that escape enter orbits similar to centaurs. Although Neptune cannot currently capture stable trojans, roughly 2.8% of the centaurs within 34 AU are predicted to be Neptune co-orbitals. Of these, 54% would be in horseshoe orbits, 10% would be quasi-satellites, and 36% would be trojans (evenly split between the and groups). The unexpected high-inclination trojans are the key to understanding the origin and evolution of the population as a whole. The existence of high-inclination Neptune trojans points to a capture during planetary migration instead of in situ or collisional formation. The estimated equal number of large and trojans indicates that there was no gas drag during capture and points to a common capture mechanism for both and trojans. The capture of Neptune trojans during a migration of the planets occurs via process similar to the chaotic capture of Jupiter trojans in the Nice model. When Uranus and Neptune are near but not in a mean-motion resonance the locations where Uranus passes Neptune can circulate with a period that is in resonance with the libration periods of Neptune trojans. This results in repeated perturbations that increase the libration of existing trojans causing their orbits to become unstable. This process is reversible allowing new trojans to be captured when the planetary migration continues. For high-inclination trojans to be captured the migration must have been slow, or their inclinations must have been acquired previously. Colors The first four discovered Neptune trojans have similar colors. They are modestly red, slightly redder than the gray Kuiper belt objects, but not as extremely red as the high-perihelion cold classical Kuiper belt objects. This is similar to the colors of the blue lobe of the centaur color distribution, the Jupiter trojans, the irregular satellites of the gas giants, and possibly the comets, which is consistent with a similar origin of these populations of small Solar System bodies. The Neptune trojans are too faint to efficiently observe spectroscopically with current technology, which means that a large variety of surface compositions are compatible with