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Didymos

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ASTEROID

Didymos

The primary of a binary asteroid system — target of NASA's DART planetary-defense test.

Orbits Sun 1 moons
  • Primary of the first binary asteroid system targeted by a spacecraft.
  • Its moon Dimorphos was struck by NASA's DART spacecraft on 26 September 2022.
  • Target of ESA's Hera mission (launched October 2024, arrival December 2026).

Physical Properties

0 km
2.26 h
0.15

Orbit

Sun
1.644 AU
0.384
3.41°
2.11 yr

Notable Moons

Dimorphos
Moon

Sources & Further Reading

Numerical values (radius, mass, orbital elements, temperatures) are drawn from NASA NSSDC Planetary Fact Sheets, JPL Horizons, and the JPL Small-Body Database. Last refreshed: 2026-04-18 18:19:27.

Didymos is a near-Earth asteroid and the primary of a binary asteroid system. Its 170 m moonlet Dimorphos was the target of NASA’s Double Asteroid Redirection Test (DART), which impacted Dimorphos on 26 September 2022 to demonstrate that kinetic impactors can change an asteroid’s orbit — a planetary-defense technique. The impact shortened Dimorphos’s orbital period around Didymos by 33 minutes. ESA’s Hera spacecraft, launched 7 October 2024, will arrive in December 2026 to characterize the system post-impact in detail.