The Didymos system
Dimorphos is the small moon of asteroid Didymos. The pair provided a measurable experiment and posed no threat to Earth. By observing the time Dimorphos took to orbit the larger body, scientists could measure the effect of the impact.
Impact and result
DART struck Dimorphos on 26 September 2022. Early analysis indicated a reduction in orbital period of about 32 minutes; subsequent observations refined the result to about 33 minutes. The measured change concerns Dimorphos’s orbit around Didymos.
An Italian contribution
The Italian Space Agency’s small LICIACube satellite observed the system after impact and the clouds of material ejected. The experiment was a step in planetary defence; it does not mean that all asteroids have been found or that every future impact can be prevented.