Smashing a moon slowed down the main asteroid ⚡ экспресс
Asteroid Didymos slowed its rotation after the DART probe slammed into its moon Dimorphos. The reason: the impact flattened Didymos, making it wider at the waist, like a figure skater spreading their arms. This 'spread' added 0.18 seconds to each rotation—less than an instant, but astronomers noticed it thanks to 20 years of observations. They monitored changes in the system's brightness as one asteroid passed in front of the other—transits—and caught the tiny lengthening of the day using brightness measurements. This is the first evidence that a kinetic impactor can not only deflect an asteroid but also permanently change its shape and rotation. And the most unexpected part? Dimorphos itself began orbiting Didymos 37 minutes faster after the impact. No matter where you look, surprises abound.
🎯 Dimorphos's orbit around Didymos shrank by 37 minutes: from 11.9 to 11.23 hours.
🎬 If in 'Armageddon' they nuke an asteroid, DART simply rammed its target—and that was enough to change not only its orbit but also its spin.