When NASA sent the DART spacecraft to collide with the asteroid Dimorphos in 2022, the US space agency demonstrated that it is possible to change the orbit of a celestial body if necessary to protect Earth. It turns out that this collision not only changed the asteroid’s path, but also its shape.
Before the encounter with DART, the asteroid looked like a slightly plump ball at the waist, but now it appears to be shaped like a watermelon, or technically a triaxial ellipsoid. Scientists made the announcement on Tuesday.
“The general understanding is that dimorphos is a loose collection of debris, ranging from dust to gravel to rock. Therefore, its overall strength is very low, making it a solid, monolithic object. “It’s much easier to deform,” said Steve Chesley, a senior scientist at NASA’s Jet Propulsion Laboratory (JPL) in California and co-author of the study published in the June 2006 issue. I am. Planetary Science Journal.
“Due to the debris pile configuration, the change in shape was very dramatic,” said Shantanu Naidu, a navigation engineer at JPL and lead study author. “By measuring the trajectory of Dimorphos before and after the collision, we were able to estimate the change in Dimorphos’ shape due to the DART collision.”
Dimorphos is a satellite of Didymos, which is defined as a near-Earth asteroid. The DART (Double Asteroid Redirection Test) mission was a proof-of-principle mission that used a spacecraft to apply a kinetic force to nudge a celestial body that could potentially collide with Earth. Dimorphos and Didymos are no real threat to Earth.
On September 26, 2022, the spacecraft collided with the 560-foot-wide (170-meter) asteroid Dimorphos, about 6.8 million miles (11 million kilometers) from Earth, at about 14,000 miles per hour (22,530 kilometers per hour). did. Didymus is approximately 0.5 miles (780 meters) in diameter.
The DART impact, which sent rocky debris from the asteroid into space, also changed the orbit that Dimorphos takes around Didymos, making it elliptical instead of circular and taking less time to complete its orbital period, or one orbit. The amount of time it takes has also varied, the scientists said. . It turns out that Dimorphos currently takes 11 hours, 22 minutes and 3 seconds to complete one revolution, 33 minutes and 15 seconds faster than before the collision.
Scientists have previously shown that the asteroid’s orbit has changed, and this study provides the most precise measurements to date.
Chesley said the asteroid’s orbital period continued to slowly decay over the weeks following the impact.
“We think this is because loose debris within the system continues to leak, carrying angular momentum and inevitably contracting the orbit,” Chesley added. Angular momentum refers to how much a rotating object’s mass is distributed around its axis and the speed at which it is rotating.
Dimorphos’ average orbital distance from Didymos is now about 3,780 feet (1,152 meters), about 120 feet (37 meters) shorter than before the collision, according to the study.
The researchers drew their conclusions about Dimorphos’ shape and orbit from observations with ground-based telescopes of how sunlight reflecting off the surfaces of two asteroids changes over time, and from observations of radio waves reflected from the asteroids. The data was derived by DART based on images acquired during the rendezvous.
We expect to learn more about these two asteroids in the near future. The European Space Agency’s Hera spacecraft is scheduled to launch in October and arrive at the end of 2026 to assess the situation.
“We are looking forward to the arrival of ESA’s Hera spacecraft, when we will be able to compare the modeled shapes with those obtained from Hera images. You can also see how much the trajectory has changed since then,” Chesley said.
