Dimorphos is a small moonlet that orbits the asteroid Didymos. It is approximately 160 meters in diameter and is part of a binary system, where Didymos is the larger body, about 780 meters wide. In September 2022, NASA's DART mission successfully impacted Dimorphos to test a method of planetary defense against potential asteroid threats. The collision aimed to change the moonlet's orbit around Didymos, demonstrating how kinetic impact could alter an asteroid's trajectory.