Research paper
Direct detection of an asteroid’s heliocentric deflection: The Didymos system after DART
This research proves that kinetic impact - essentially ramming a spacecraft into an asteroid - can successfully change an asteroid's path through space. With potentially dangerous asteroids regularly discovered near Earth, having a tested method to deflect them could literally save civilization. The fact that targeting the smaller object in a binary system works effectively gives planetary defenders more strategic options when facing future asteroid threats.
NASA crashed a spacecraft into an asteroid moon called Dimorphos in 2022, and scientists have now measured that this impact actually nudged the entire asteroid system slightly off its path around the Sun. This is the first time humans have measurably changed how a celestial body orbits the Sun, proving that we can potentially deflect dangerous asteroids heading toward Earth.
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The DART spacecraft impact changed the Didymos system's orbit around the Sun by slowing it down by 11.7 micrometers per second
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This marks the first human-caused measurable change to a celestial body's orbit around the Sun
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The momentum from the impact was amplified by a factor of 2.0, meaning the effect was twice as strong as the direct impact alone
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Dimorphos (the target) has a much lower density than Didymos - about 1540 vs 2600 kg per cubic meter
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Hitting the smaller moon in a binary asteroid system can effectively deflect the entire system, expanding planetary defense options
In September 2022, NASA's Double Asteroid Redirection Test (DART) spacecraft crashed into Dimorphos and demonstrated the kinetic impact method of protecting Earth from asteroids. A fraction of the impulse delivered to Dimorphos was also imparted onto the Didymos system's barycenter, changing its heliocentric orbit. Here, we present the first-ever measurement of human-caused change in the heliocentric orbit of a celestial body. Thanks to stellar occultation and radar measurements, we estimate that the Didymos system experienced an along-track velocity change of -11.7 ± 1.3 micrometers per second. We constrain the heliocentric momentum enhancement factor for DART at 2.0 ± 0.3 and the bulk densities of Didymos and Dimorphos at 2600 ± 140 and 1540 ± 220 kilograms per cubic meter, respectively. Our results demonstrate that targeting the secondary asteroid in binary systems constitutes a possible strategy for kinetic impact deflection, adding to humanity's planetary defense capabilities.