It worked! Humanity has deliberately moved a celestial body for the first time.
As a test of a possible asteroid deflection scheme, NASA’s DART spacecraft shortened the orbit of asteroid Dimorphos by 32 minutes — a much bigger change than astronomers expected.
The Double Asteroid Redirection Test, or DART, rammed into the small asteroid at about 22,500 kilometers per hour on Sept.SN: 26-09-22). The goal was to bring Dimorphos a little closer to the larger asteroid in question, Didymos.
Neither Dimorphos nor Didymos pose a threat to Earth. DART’s mission was to help scientists figure out whether a similar impact could push a potentially dangerous asteroid away from danger before it reaches our planet.
The experiment was a resounding success. Before the impact, Dimorphos orbited Didymos every 11 hours and 55 minutes. After, the track was 11 hours and 23 minutesNASA announced Oct. 11 in a press conference.
“For the first time ever, humanity has changed the orbit of a planetary body,” said Lori Glaze, director of NASA’s division of planetary science.
Four telescopes in Chile and South Africa observed the asteroids every night after the impact. The telescopes can’t see the asteroids individually, but they can detect periodic changes in brightness as the asteroids eclipse each other. All four telescopes saw eclipses corresponding to an orbit of 11 hours and 23 minutes. The result was confirmed by two planetary radar facilities, which bounced radio waves off the asteroids to directly measure their orbits, said Nancy Chabot, a planetary scientist at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland.
The minimum change for the DART team to declare success was 73 seconds – a hurdle the mission exceeded by more than 30 minutes. The team thinks the spectacular plume of debris that kicked up the impactor gave the mission extra power. The impact itself gave the asteroid some momentum, but the debris flying off in the other direction pushed it even more — like a temporary rocket motor.
“This is a very exciting and promising result for planetary defense,” Chabot said. But the change in orbital time was only 4 percent. “It just gave him a little push,” she said. So knowing that an asteroid is approaching is critical to future success. For something akin to working on an asteroid headed for Earth, “you’d want to do it years in advance,” Chabot said. An emerging space telescope called Surveyor for terrestrial objects is one of many projects designed to provide that early warning.