March 6, 2026
3 my read
Add us on GoogleAdd SciAm
NASA changed an asteroid’s orbit around the Sun, a first for mankind
Smashing a spacecraft into a binary asteroid system has managed to change its orbit around the sun, a new analysis reveals
The asteroid binary, Didymos and Dimorphos.
In September 2022, NASA smashed a spacecraft into an asteroid. Called Dimorphos, the rock is the smaller asteroid in a binary pair; it orbits a larger one called Didymos. Slamming into Dimorphos told the scientists a number of things: the collision managed to throw the asteroid slightly off course, slowing its orbit around its larger companion by about 30 minutes, and suggested that a similar method could help defend Earth from intruding asteroids.
But now the mission has revealed something even more profound: by slowing Dimorphos’ orbit, NASA has managed to change the entire binary system’s orbit around the Sun. The act of changing a natural object’s orbit around our home star marks a first for humanity.
In a study published Friday in the journal The progress of science, scientists explain how the initial collision with Dimorphos slowed the binary’s entire solar orbit by about 12 microns per second. The new data could help NASA better prepare to deflect asteroids that could one day threaten the planet, the researchers say.
On supporting science journalism
If you like this article, please consider supporting our award-winning journalism by subscribes. By purchasing a subscription, you help secure the future of impactful stories about the discoveries and ideas that shape our world today.
“If (an asteroid) is ever on its way to hitting Earth, we can now say with greater confidence that we have the ability to push them around and away from Earth,” said the study’s lead author Rahil Makadia, who was a planetary defense scientist at the University of Illinois Urbana-Champaign when it was conducted.
Dimorphos and Didymos pose no danger to Earth. But they were chosen as targets for the Double Asteroid Redirection Test (DART) to assess our planetary defense capabilities, Makadia explains. DART involved ramming a 570 kilogram spacecraft moving at around 22,530 kilometers per hour into Dimorphos in an attempt to slow its journey around Didymos. Still, the researchers thought the test might just change the pair’s heliocentric orbit as well.
“This was also something we had thought about even before the DART effect,” says Makadia. “But what we didn’t know was to what extent this would happen and whether we would be able to measure it at all.”
Makadia and his team combined radar measurements and observations of the binary system as it passed in front of the Sun to compare the asteroids’ pre-DART orbit with their post-impact orbit. The system’s roughly two-year journey around the sun was reduced by about 11.7 microns per second, or about 370 meters per year, the analysis found.
The finding is “really cool,” said Jay McMahon, an associate professor of aerospace engineering at the University of Colorado Boulder. McMahon has worked with the DART team in the past but was not involved in the new study. “Like any experiment, you can make a prediction about what will happen, but then you have to take the measurements to prove it,” he says. “And so, this proves it.”
Makadia and his colleagues also calculated the collision’s “momentum enhancement factor,” which essentially measured how much the loss of rocks, dust, and other material during the impact contributed to the change in orbit. “That basically doubled the pressure of the spacecraft alone,” says Makadia. The team also estimated the mass of each asteroid separately for the first time.
The findings could have broader implications beyond planetary defense, notes Masatoshi Hirabayashi, another DART researcher who was not directly involved in the new study and an associate professor of aerospace engineering at the Georgia Institute of Technology. Knowing the asteroids’ respective masses and densities can help scientists better understand their structure, “a key piece of information about how this binary asteroid formed,” he says.
More data is coming soon: later this year, the European Space Agency’s Hera mission will take a closer look at DART’s effect on Dimorphos and Didymos, including the post-collision impact crater.
“When we get the measurements from (Hera), we can come to these numbers from a completely independent way and confirm them and maybe build on them as well,” says Makadia.
It’s time to stand up for science
If you liked this article, I would like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in its two-century history.
I have been one Scientific American subscriber since I was 12 years old, and it helped shape the way I see the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does for you too.
If you subscribe to Scientific Americanyou help ensure our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten laboratories across the United States; and that we support both budding and working scientists at a time when the value of science itself is too often not recognised.
In return, you receive important news, captivating podcasts, brilliant infographics, can’t-miss newsletters, must-see videos, challenging games, and the world of science’s best writing and reporting. You can even give someone a subscription.
There has never been a more important time for us to stand up and show why science is important. I hope you will support us in that mission.
