It worked! Humanity, for the first time, has deliberately moved a celestial object.
As a test of a possible asteroid deflection scheme, NASA’s DART spacecraft shortened the orbit of asteroid Dimorphos by 32 minutes, a much larger change than astronomers expected.
The Double Asteroid Redirection Test, or DART, collided with the small asteroid at about 22,500 kilometers per hour on September 26 (Serial number: 09/26/22). The goal was to bring Dimorphos a little closer to the largest asteroid it orbits, Didymos.
Neither Dimorphos nor Didymos pose any threat to Earth. DART’s mission was to help scientists determine if a similar impact could push a potentially dangerous asteroid away before it hits our planet.
The experiment was a resounding success. Before the impact, Dimorphos orbited Didymos every 11 hours and 55 minutes. After, the orbit was 11 hours and 23 minutesNASA announced on October 11 at a press conference.
“For the first time in history, humanity has changed the orbit of a planetary body,” said Lori Glaze, director of NASA’s planetary science division.
Four telescopes in Chile and South Africa observed the asteroids every night after the impact. Telescopes cannot see asteroids separately, but they can detect periodic changes in brightness as asteroids outshine each other. All four telescopes saw eclipses consistent with an orbit of 11 hours and 23 minutes. The result was confirmed by two planetary radar facilities, which bounced radio waves off asteroids to measure their orbits directly, said Nancy Chabot, a planetary scientist at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland.
The minimum turnaround for the DART team to declare success was 73 seconds, a hurdle the mission cleared in more than 30 minutes. The team believes the spectacular column of debris kicked up by the impactor gave the mission an extra boost. The impact itself gave the asteroid some lift, but debris flying in the other direction pushed it further, like a temporary rocket motor.
“This is a very exciting and promising result for planetary defense,” said Chabot. But the change in orbital period was only 4 percent. “It just gave it a little push,” he said. Therefore, knowing that an asteroid is approaching is crucial to future success. For something similar to work on an Earth-bound asteroid, “you’d want to do it years in advance,” Chabot said. An upcoming space telescope called Near-Earth Asteroid Surveyor it is one of many projects aimed at giving that early warning.