Researchers have determined that NASA’s 2022 Double Asteroid Redirection Test (DART) mission is the first to cause a deliberate change in the heliocentric orbit of a celestial body – in this case, a binary asteroid system. The DART mission intentionally crashed a spacecraft into the asteroid Dimorphos, which orbits the larger asteroid Didymos as the pair orbits the sun. The mission’s goal was to determine whether human intervention could result in the deflection of asteroids away from Earth. The new research follows up on initial results, which showed that DART was able to slow and alter the orbit of Dimorphos around Didymos; now, the researchers have concluded that the impact also slowed the heliocentric orbit of the entire Didymos system by more than 10 micrometers per second. Rahil Makadia and colleagues analyzed 22 stellar occultation measurements taken since the DART impact, 5,955 ground-based right ascension and declination pairs, and other data to determine the full extent of the deflection. The results showed two main causes for the orbital change: the spacecraft’s impact itself and additional momentum from debris ejected outside of the binary system. Both the impact on Dimorphos and the escaped ejecta altered the trajectory and speed of Didymos system’s barycenter, or central orbital point, which also determines the system’s orbital path around the sun. The full extent of the heliocentric momentum enhancement from DART has not yet been determined, but should be measurable with future data. To that end, the European Space Agency’s Hera mission is now en route to the Didymos system, set to arrive in November 2026. “By demonstrating that asteroid deflection missions such as DART can effect change in the heliocentric orbit of a celestial body, this study marks a notable step forward in our ability to prevent future asteroid impacts on Earth,” Makadia et al. write.