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Ida

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ASTEROID

Ida

The first asteroid discovered to have a moon — Dactyl — photographed by Galileo in 1993.

Orbits Sun 1 moons

Physical Properties

16 km
4.634 h
0.238

Orbit

Sun
2.862 AU
0.0464
1.133°
4.84 yr

Notable Moons

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.

243 Ida is a main-belt asteroid imaged at close range by NASA’s Galileo spacecraft on 28 August 1993 during its cruise to Jupiter. Galileo’s images revealed Ida’s tiny moon Dactyl (~1.4 km across) — the first confirmed asteroid moon ever observed.