Near-Earth object focused on asteroids and short-period comets. CNEOS even restricts its definition of NECs to short-period comets—, 107 such objects have been discovered. , only 20 comets have been observed to pass within of Earth, including 10 which are or have been short-period comets. Two of these comets, Halley's Comet and 73P/Schwassmann–Wachmann, have been observed during multiple close approaches. The closest observed approach was 0.0151 AU (5.88 LD) for Lexell's Comet on July 1, 1770. After an orbit change due to a close approach of Jupiter in 1779, this object is no longer a NEC. The closest approach ever observed for
Claimed moons of Earth the Earth–Moon system, whereas the orbit of a quasi-satellite would negligibly change if Earth and the Moon were suddenly removed because a quasi-satellite is orbiting the Sun on an Earth-like orbit in the vicinity of Earth. Earth possesses one known trojan, a small Solar System body caught in the planet's gravitationally stable Lagrangian point. This object, is roughly 300 metres across. Like quasi-satellites, it orbits the Sun in a 1:1 resonance with Earth, rather than Earth itself. On 14 September 2006, an object estimated at 5 meters in diameter was discovered in near-polar orbit around Earth. Originally thought to be