For the first time in history, mankind has changed the orbit of a celestial body around the Sun

The mission that moved the space rock

The goal of the DART mission was simple but ambitious. To test the “kinetic impactor” technique as a method of defending the Earth from potentially dangerous space objects. The target was a binary asteroid system, which means that two asteroids are gravitationally bound and orbit each other as they travel together around the Sun.

The larger one, called Didymos, is about 780 meters in diameter, while its target, the smaller Dimorphos, is only about 160 meters wide. The idea was that a hit to the smaller č link of the pair could move the entire system. Although neither Didymos nor Dimorphos ever posed a threat to Earth, their system was the perfect laboratory for testing this key defense technology.

A new study, published in the journal Science Advances, confirmed what scientists had hoped for. The impact of the DART spacecraft slowed the orbital speed of the entire binary system by about 11.7 micrometers per second, which is equivalent to a speed of about 4.3 centimeters per hour. Although it seems negligibly small, on a cosmic scale and over a long period of time, such a change can mean the difference between a collision and safe passage.

In particular, the orbital period of the system around the Sun, which lasts 770 days, is permanently shortened by approximately 0.15 seconds.

Double kick and moć shard

How could such a small impact produce a measurable effect on the scale of the entire Sun system? The answer lies in the phenomenon that scientists call the “momentum amplification factor” (beta). When the DART spacecraft hit Dimorphos, it launched a huge cloud of rocky debris into space. That material, which flew away from the asteroid, acted like a powerful thruster, giving the system an additional impulse. Research has shown that this amplification factor was approximately two, which means that the ejected debris doubled the force produced by the collision of the spacecraft itself.

The success was also contributed by the fact that Dimorphos is a “heap of silence”, that is, a loose accumulation of rocks and dust held together by weak gravity, rather than a type of rock, which made it possible to eject a larger amount of material.

Proving that DART had a measurable impact on both asteroids required incredible precision. Scientists relied on radar and ground observations, but a technique known as “stellar occultation” played a key role.

It is a phenomenon in which an asteroid passes right in front of a distant star, causing its light to partially “blink” seconds. This method enables extremely precise measurement of the speed, shape and position of asteroids. Measuring occultations is extremely challenging: astronomers must be in the right place at the right time, often at remote locations with multiple observing stations.

The team relied on a global network of volunteer astronomers who recorded 22 key occultations between October 2022 and March 2025. Without their dedication, this achievement would not have been possible.

The success of the DART mission and the confirmation of the change in the heliocentric orbit have enormous implications for the future of planetary defense.

​- This is a tiny change in orbit, but given enough time, even a tiny change can grow into a significant deflection – said Thomas Statler, lead scientist for small bodies of the Sun’s system at NASA headquarters.

​- The team’s incredibly precise measurement reaffirms kinetic impact as a technique to defend Earth from asteroid threats. –

The key, of course, is to detect potentially dangerous objects early enough, years or decades before a potential collision. For this purpose, NASA is developing the NEO Surveyor mission, a new generation space telescope designed specifically to hunt hard-to-see asteroids. In the meantime, the European Space Agency (ESA) will send its Hera mission, which should reach the Didymos system at the end of 2026 and conduct a detailed “crime scene investigation”, analyzing the impact crater and further specifying the physical properties of these space bodies.