near-Earth asteroid
Didymos
A binary near-Earth asteroid whose moonlet Dimorphos was struck by NASA's DART in 2022 – humanity's first planetary defence test.
- Distance from Earth today
- 196.7 million km1.315 AU · light: 10 min 56 s
- Distance from the Sun today
- 179.8 million km1.202 AU
- As of
- 4 November 2026position from NASA/JPL orbital elements
Where it is today
Top view of the plane of Earth’s orbit, compressed distance scale. Open on the big map with the time slider →
Facts
- Diameter
- 0.78 km
- Dimensions
- 0.797 × 0.783 × 0.761 km
- Density
- 2,170 kg/m³
- Rotation period
- 2.3 h
- Semi-major axis
- 1.643 AU (245.8 million km)
- Perihelion
- 1.013 AU
- Aphelion
- 2.272 AU
- Orbital period
- 2.11 years
- Orbital eccentricity
- 0.383
- Orbital inclination
- 3.4°
- Last perihelion
- 28 November 2024
- Next perihelion
- 6 January 2027
- Minimum orbit distance from Earth’s orbit (MOID)
- 0.040 AU (5.92 million km)
Source of the figures: JPL Small-Body Database (public domain).
Discovery: 1996 – Spacewatch survey
Description
Didymos is a near-Earth asteroid discovered by the Spacewatch survey in 1996; its name means "twin" in Greek, because it has a small moon, Dimorphos. Neither poses any threat to Earth, which made the pair an ideal target for testing asteroid deflection. On 26 September 2022 NASA's DART spacecraft deliberately crashed into Dimorphos, and observations from Earth showed that the impact shortened its orbit around Didymos by much more than the minimum required for success, while also blasting out a long trail of debris. The Italian cubesat LICIACube photographed the aftermath, and ESA's Hera mission was launched to examine the system in detail.