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| Orbital characteristics | |
|---|---|
| Orbit type | Main belt (Koronis family) |
| Semimajor axis | 2.86108 AU |
| Eccentricity | 0.04614 |
| Orbital period | 4.84 y |
| Inclination | 1.13664° |
| Satellites | 1 |
| Physical characteristics | |
| Diameter | 56×24×21 km |
| Mass | 1×1017 kg |
| Density | 2.5 g/ cm³ |
| Rotation period | 4h 37m |
| Spectral classAn asteroid is a small, solid object in our Solar System, orbiting the Sun. An asteroid is an example of a minor planet (or planetoid , which are much smaller than planets. The asteroids are believed to be remnants of the protoplanetary disc which were no | SApproximately 17% of all known asteroids are of an S-type (for stony composition. S-types are moderately bright (with an albedo of 0. 22) and consist of metallic nickel- iron mixed with iron- and magnesium- silicates. They dominate the inner to central ma |
| AlbedoNote: This article discusses the physical or planetological property of albedo. For other usage, see Albedo (disambiguation). The albedo is a measure of reflectivity of a surface or body. It is the ratio of electromagnetic radiation reflected to the amoun | 0.24 |
| History | |
| Discoverer | J. PalisaJohann Palisa ( December 6 1848 May 2 1925) was an Austrian astronomer, born in Opava, Czech Republic (then part of Austrian Empire). He was a prolific discoverer of asteroids, discovering 122 in all, from 136 Austria in 1874 to 1073 Gellivara in 1923., 18841884 is a leap year starting on Tuesday (click on link to calendar). Events January 4 The Fabian Society is founded in London. February 1 Edition one of the Oxford English Dictionary is published. March 13 The siege of Khartoum, Sudan begins (ends on Janu |
243 Ida is an asteroidAn asteroid is a small, solid object in our Solar System, orbiting the Sun. An asteroid is an example of a minor planet (or planetoid , which are much smaller than planets. The asteroids are believed to be remnants of the protoplanetary disc which were no that was imaged by the Galileo probe on August 28August 28 is the 240th day of the year in the Gregorian Calendar (241st in leap years), with 125 days remaining. Events Wednesday, August 28, 475 The German general Orestes forces western Roman Emperor Julius Nepos to flee his capital of Ravenna and appoi, 19931993 is a common year starting on Friday and marked the Beginning of the International Decade to Combat Racism and Racial Discrimination (1993-2003 Events January January 1 Czechoslovakia divides. Establishment of independent Slovakia and Czech Republic.. The probe discovered that Ida had a small moon, an asteroid dubbed Dactyl, only 1.4 km in diameter; this was the first asteroid moon to be discovered. Some researchers believe that Dactyl formed from debris ejected from Ida by cratering, while others suggest that Ida and Dactyl formed as a pair a billion or more years ago when Ida's parent body was disrupted. Both of these theories present difficulties that remain unresolved at this time. Since the discovery of Dactyl, other observations have suggested that asteroid moons are not uncommon.
Ida is named after Ida, a Cretan nymph in Greek mythology who lived on a mountain that bore her name.
The color picture is made from images taken by the imaging system on the Galileo spacecraft about 14 minutes before its closest approach to asteroid 243 Ida on August 28, 1993. The range from the spacecraft was about 10,500 kilometers (6,500 miles). The images used are from the sequence in which Ida's moon was originally discovered; the moon is visible to the right of the asteroid. This picture is made from images through the 4100- Å (violet), 7560 Å ( infrared) and 9680 A (infrared) filters. The color is 'enhanced' in the sense that the CCD camera is sensitive to near infrared wavelengths of light beyond human vision; a 'natural' color picture of this asteroid would appear mostly gray.
Shadings in the image indicate changes in illumination angle on the many steep slopes of this irregular body as well as subtle color variations due to differences in the physical state and composition of the soil ( regolith). There are brighter areas, appearing bluish in the picture, around craters on the upper left end of Ida, around the small bright crater near the center of the asteroid, and near the upper right- hand edge (the limb). This is a combination of more reflected blue light and greater absorption of near infrared light, suggesting a difference in the abundance or composition of iron- bearing minerals in these areas.
Ida's moon also has a deeper near-infrared absorption and a different color in the violet than any area on this side of Ida. The moon is not identical in spectral properties to any area of Ida in view here, though its overall similarity in reflectance and general spectral type suggests that it is made of the same rock types basically. These data, combined with study of further imaging data and more detailed spectra from the Near Infrared Mapping Spectrometer, may allow scientists to determine whether the larger parent body of which Ida, its moon, and some other asteroids are fragments was a heated, differentiated object or made of relatively unaltered primitive chondritic material.
See also: List of geological features on 243 Ida and Dactyl.
Asteroids visited by spacecraft Binary asteroids