DART Mission Successfully Alters Asteroid Orbit, Pioneering Planetary Defense
In a landmark achievement for planetary defense, scientists have confirmed that NASA’s DART (Double Asteroid Redirection Test) mission not only altered the orbit of the asteroid Dimorphos, but also measurably shifted the orbit of the asteroid system around the sun. The findings, published on in Science Advances, represent the first time a human-made object has demonstrably changed the path of a celestial body around our star.
The DART mission, intentionally crashed a spacecraft into Dimorphos, a small moon orbiting the larger asteroid Didymos, in . The primary goal was to test a method of planetary defense – specifically, whether a kinetic impact could deflect an asteroid. Initial results, within a month of the impact, showed that Dimorphos’s orbital period around Didymos had shortened by 32 minutes.
However, the recent analysis reveals a more comprehensive effect. Because Didymos and Dimorphos are a binary system – meaning they orbit each other around a shared center of mass – any change to one inevitably affects the other. Astronomers meticulously tracked the pair’s motion, observing how long it took them to orbit the sun. They discovered that the 770-day orbital period around the sun changed by a fraction of a second following the DART impact.
“Those rocky runaways took some momentum away from the duo and changed their joint motion around the sun,” explained Rahil Makadia, a planetary defense researcher at the University of Illinois Urbana–Champaign. The impact ejected debris from Dimorphos, and some of these fragments escaped the gravitational pull of the asteroid pair, effectively altering their combined momentum and, their orbit around the sun.
The measurements were obtained through a technique called stellar occultation. This involves observing the asteroids as they pass in front of distant stars, momentarily dimming the starlight. These “blinks” are predictable, allowing astronomers to precisely measure the asteroids’ positions, and movements. Remarkably, many of these crucial measurements were made by amateur astronomers who traveled to remote locations, such as the Australian outback, to observe these events.
“Oftentimes it’s amateur astronomers going out in the middle of nowhere to track Didymos based on predictions,” Makadia noted. “There was an observer who drove two days each way into the Australian outback to get these measurements.” A total of 22 such measurements, collected between and , were used to calculate the change in the asteroids’ orbital period – approximately 150 milliseconds slower than before the impact.
While Didymos and Dimorphos pose no threat to Earth, this successful demonstration of asteroid deflection has significant implications for planetary defense. The European Space Agency’s Hera spacecraft is currently en route to the Didymos system and is expected to arrive later in to conduct further observations and provide additional data. Hera’s arrival will allow for a more detailed assessment of the impact’s effects and refine our understanding of asteroid deflection techniques.
The DART mission’s success provides valuable insights into how to potentially protect Earth from future asteroid impacts. The ability to deliberately alter an asteroid’s orbit, even by a small amount, could be crucial in preventing a catastrophic collision. As Makadia emphasized, this knowledge is essential “in case we need to do a kinetic impact for real.”
The mission underscores the importance of continued research and development in planetary defense, as well as the power of collaboration between professional astronomers and dedicated amateur observers. The data gathered from DART and Hera will undoubtedly inform future strategies for safeguarding our planet from potential asteroid threats.