NASA heralded a new study published Friday documenting a first for humanity — "the first time a human-made object has measurably altered the path of a celestial body around the Sun."
It was 2022's DART mission where NASA crashed a spacecraft into an asteroid — and the experiment "could have implications for protecting Earth from future asteroid strikes," writes ScienceNews:
A spacecraft slowed the orbit of a pair of asteroids around the sun by more than 10 micrometers per second... Within a month, researchers showed that the impact shortened Dimorphos' 12-hour orbit by 32 minutes. Some of the rocks knocked off of Dimorphos fled the vicinity completely, escaping the gravitational influence of the Dimorphos-Didymos pair, says planetary defense researcher Rahil Makadia of the University of Illinois Urbana-Champaign. Those rocky runaways took some momentum away from the duo and changed their joint motion around the sun.
To figure out how much that motion was affected, astronomers watched the asteroids pass in front of distant stars, dimming some of the stars' light like a tiny eclipse. These blinks, called stellar occultations, can be visible from anywhere on Earth and are predictable in advance... Calculating how far off occultation timings were from predictions revealed that the asteroids' orbit around the sun was about 150 milliseconds slower than before the DART impact...
Didymos and Dimorphos are not a threat to Earth, Makadia says, and weren't before DART. But knowing how a deliberate impact changes one asteroid's orbit can help make defense plans against another, "in case we need to do a kinetic impact for real."
The researchers spent nearly two and a half years to collect 22 measurements of the asteroid's post-crash position, relying on amateur astronomers "to go out into the middle of nowhere and observe the necessary stellar occultations," acvcording to their paper. Planetary defense researcher even tells ScienceNews "There was an observer who drove two days each way into the Australian outback to get these measurements."
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