NASA mission changed orbit of asteroid around Sun

In September 2022, NASA’s Double Asteroid Redirection Test (DART) spacecraft was intentionally crashed into the asteroid moonlet Dimorphos. According to a paper published in Science Advances in March 2026, the impact didn’t just change the motion of Dimorphos around its larger companion asteroid, Didymos; it also shifted the orbit of both asteroids around the Sun.

The published study was conducted by former Illinois aerospace engineering student Rahil Makadia (B.S. ’20, Ph.D. ’25) and Illinois aerospace engineering professor Siegfried Eggl, Makadia’s advisor, along with 12 international collaborators. The DART experiment – the first-ever test of human asteroid deflection -- preceded the voyage of a European Space Agency probe dubbed Hera, which will study the aftermath of the DART impact. The Hera spacecraft is expected to arrive at the asteroid in late 2026.

“Being able to show that DART was the first mission to actually change an asteroid’s orbit about the Sun... is simply amazing. This study really shows how powerful the combination of ultra-high-precision astrometry and modern astrodynamics has become,” Eggl said.

Didymos and Dimorphos orbit each other around a shared center of mass in a configuration known as a binary system, so changes to one asteroid affect the other.

As detailed in the paper, their 770-day orbital period around the Sun changed by a fraction of a second after the impact. It marks the first time a human-made object has measurably altered the path of a celestial body around the Sun.

“This is a tiny change to the orbit, but given enough time, even a tiny change can grow to a significant deflection,” said Thomas Statler, a NASA scientist. “The team’s amazingly precise measurement again validates kinetic impact as a technique for defending Earth against asteroid hazards and shows how a binary asteroid might be deflected by impacting just one member of the pair.”

Photo Credit: NASA

When DART struck Dimorphos, the impact blasted a huge cloud of rocky debris into space, altering the shape of the asteroid. Because the debris carried its own momentum away from the asteroid, it gave Dimorphos an explosive thrust — what scientists call the momentum enhancement factor. More debris being kicked out means more oomph. According to the team, the momentum enhancement factor for DART’s impact was about two, meaning that the debris loss doubled the punch created by the impact.

Earlier research showed that the smaller asteroid’s 12-hour orbital period around its larger companion was shortened by 33 minutes. The impact also shortened the binary system’s orbital period around the Sun by 0.15 seconds.

“The change in the binary system’s orbital speed was about 11.7 microns per second, or 1.7 inches per hour,” said Makadia, who led this study. “Over time, such a small change in an asteroid’s motion can make the difference between a hazardous object hitting or missing our planet.”

Although Didymos was not on an impact trajectory with Earth and it was impossible for the DART mission to put it on one, that change in orbital speed underscores the role spacecraft — aka “kinetic impactors,” in this context — could play if a potentially hazardous asteroid is ever found to be on a collision course. The key is to detect near-Earth objects far enough in advance to be able to send a kinetic impactor — and those detections, in turn, depend on measurements of “stellar occultations”: the passages of objects like asteroids in front of stars.

Those measurements are challenging. Astronomers must be in the right place at the right time with several observing stations, sometimes miles apart, to track the predicted path of an asteroid in front of a specific star. The team relied on volunteer astronomers around the globe who recorded 22 stellar occultations between October 2022 and March 2025.

“When combined with years of existing ground-based observations, these stellar occultation observations became key in helping us calculate how DART had changed Didymos’ orbit,” said study co-lead Steve Chesley of NASA’s Jet Propulsion Laboratory.

Studying changes in Didymos’ motion also helped the researchers calculate the densities of both asteroids. Dimorphos is slightly less dense than previously thought, supporting the theory that it formed from rocky debris shed by a rapidly spinning Didymos. This loose material eventually clumped together to form Dimorphos.