Asteroid 243, discovered in 1884 by the Austrian astronomer Johann Palisa (1848–1925). It has a satellite, Dactyl, probably a fragment from the same parent body that broke up. Ida, an S-type asteroid, measures 54 × 24 × 15 km and rotates in a period of 4.6 hours about its shortest axis. It is a member of the Koronis family. Ida’s orbit has a semimajor axis of 2.86 au, period 4.84 years, perihelion 2.74 au, aphelion 2.98 au, and inclination 1°.1.
http://photojournal.jpl.nasa.gov/catalog/PIA00069
A low-density asteroid (2.9 g/cm3) with a composition comparable to that of chondrite meteorites. An asteroid from the Koronis family, it has an irregular size of 58 × 38 km and orbits the Sun between the planets Mars and Jupiter at a distance of around 270 million km. The Galileo spacecraft discovered a satellite orbiting Ida—the first natural satellite of an asteroid ever discovered. The satellite, known as Dactyl, is 1.6 × 1.2 km, and is surprisingly round for such a small celestial body. It orbits Ida at a distance of approximately 90 km.
A solar system asteroid (No. 243), measuring 58 × 23 km; approximate mass 1017 kg; rotational period 4.633 hours; orbital period 4.84 years. Images of Ida from Galileo, taken on 23 August 1993, showed it has a small satellite, later named Dactyl.
- virgella
- Virgellina
- Virgilian
- Virginia Campaigns (July 1861–65)
- Virginius incident (1873)
- virgin medium
- Virgo
- Virgo A
- Virgo Cluster
- Virgo Supercluster
- virial coefficients
- virial equation
- virial equation of state
- virial theorem
- virion
- viroid
- virology
- Virtanen, Artturi Ilmari
- VIRTIS
- virtual
- virtual address
- virtual bank
- virtual call service
- virtual cathode
- virtual circuit