• Literally ‘kissing’, but used in astronomy to denote the path, touching the actual one taken by a comet or other body in the solar system, which it would adopt if every body in the universe except itself and the Sun were removed. This allows the perturbation due to the planets’ gravitation to be discounted. In studies of the outer solar system it is sometimes necessary to use osculating elements of the orbits of the giant planets and Pluto to correct for their gravitational influence on each other.