NASA’s DART spacecraft changed a binary asteroid’s orbit around the sun, in a first for a human-made object

When NASA crashed a spacecraft into the asteroid moonlet Dimorphos in 2022, it altered both Dimorphos’ orbit around its parent asteroid, Didymos, and the two objects’ orbit around the sun, according to new research. NASA’s Jet Propulsion Laboratory (JPL) said in a press release that this “marks the first time a human-made object has measurably altered the path of a celestial body around the Sun.” It’s a promising result as scientists work to find a feasible method of defending Earth from hazardous space objects.

The Double Asteroid Redirection Test (DART) mission was designed to demonstrate one possible way of deflecting such an object, targeting the non-threatening moonlet Dimorphos, which is about 560 feet wide. NASA quickly declared it a success after its initial analysis showed the planned collision shortened Dimorphos’ orbit around Didymos, the larger of the two objects in the binary asteroid system. In a follow-up study published in 2024, a team at NASA’s JPL reported that Dimorphos’ orbital period had been trimmed by about 33 minutes, as its path was nudged roughly 120 feet closer to Didymos than before. The latest study now indicates that the whole binary system was affected, not just Dimorphos.

Didymos and Dimorphos have a 770-day orbital period around the sun, which lead author Rahil Makadia said has been changed by “about 11.7 microns per second, or 1.7 inches per hour.” That might not sound like much, but according to Makadia, “Over time, such a small change in an asteroid’s motion can make the difference between a hazardous object hitting or missing our planet.”