(243) Ida
Asteroid· orbits the Sun
(243) Ida is a stony (S-type) main-belt asteroid of the Koronis family, about 60 km long and irregularly shaped, imaged up close by NASA's Galileo spacecraft on its way to Jupiter in 1993. Those images revealed that Ida has a small moon, Dactyl — the first satellite ever found around an asteroid.
Open in 3D viewSee (243) Ida in the live, interactive 3D map
Key facts
Radius
16.7 km
Distance from Sun
2.86 AU
Orbital period
4.85 years
Eccentricity
0.04611
Rotation
4.63 hours
Science
Physical
- Dimensions
- 59.8 × 25.4 × 18.6 km · approx. triaxial diameter
- Rotation period
- 4.63 hours
Orbital
- Semi-major axis
- 2.86 AU
- Eccentricity
- 0.04611
- Inclination
- 1.13 °
- Orbital period
- 4.85 years
- Perihelion
- 2.73 AU
- Aphelion
- 3 AU
- Mean orbital velocity
- 17.6 km/s
Discovery
- Discovered
- September 29, 1884
- Discoverer
- Johann Palisa
Composition
- Make-up
- An S-type asteroid of silicate rock (olivine and pyroxene) with some metal, a member of the Koronis collisional family. Its surface is heavily cratered and reddened by space weathering.
Radiation & temperature
- Insolation
- 0.122 S⊕ · 12% of the sunlight Earth receives
- Geometric albedo
- 0.24
- Equilibrium temperature
- 154 K (-120 °C)
Discovery & history
- Discovered
- September 29, 1884
- By
- Johann Palisa
(243) Ida was discovered on 29 September 1884 by Johann Palisa at the Vienna Observatory, one of the many main-belt asteroids he found. It drew little special attention until NASA's Galileo spacecraft flew past it on 28 August 1993 on the way to Jupiter and returned the first close-up images — which, months later, revealed that Ida has a tiny moon, Dactyl.
Images
Images from open archives · credit shown per image