26 Sept 2022

Dimorphos orbital period shortened by 33 minutes after DART impact

Space and aerospace
AI illustration · Illustrative scene, not a photograph of the specific device or experiment.

What was demonstrated

Earth-based lightcurve and radar observations measured the orbital period of Dimorphos around Didymos changing by -33.0 ± 1.0 minutes (3σ) after NASA's DART spacecraft struck it. Two independent methods gave identical values. A simple momentum-transfer estimate from the spacecraft alone predicted a change of about 7 minutes, so the authors infer that ejecta carried substantial additional momentum.

Why it matters

The measured change is about four to five times the momentum-transfer prediction, which suggests that ejected material can greatly increase the effect of a kinetic impactor. This is relevant to kinetic impact as one planetary defence option, though the result comes from a single small asteroid pair.

Caveats

  • The ejecta contribution is inferred from the measured period change. The authors state that estimating the change in Dimorphos's orbital velocity needs modelling beyond the paper's scope.
  • Ejecta contaminated the photometry, and some radar and astrometry measurements relied on stated assumptions and de-weighted or inflated uncertainties.
  • Post-impact lightcurve observations ended on 10 October 2022 because bright moonlight reduced precision.
  • The result applies to Didymos and Dimorphos only and does not show how a kinetic impact would work on other asteroids.

Technology profiles

Sources

  1. peer reviewed paper
    Orbital period change of Dimorphos due to the DART kinetic impact
    Cristina A. Thomas, Shantanu P. Naidu, Peter Scheirich et al.. Nature, 1 Mar 2023. DOI: 10.1038/s41586-023-05805-2.

Last reviewed 22 Oct 2026.