243 Ida I Dactyl
243 Ida is an S-type asteroid located in the asteroid belt between Mars and Jupiter. Discovered in 1884, it is named after a mythical Greek nymph and is characterized by its irregular shape, with a diameter of approximately 31 kilometers (19.3 miles) and a surface marked by numerous craters, indicating a long history of collisions with other celestial objects. The asteroid is estimated to be over a billion years old, offering valuable insights into the early solar system.
Ida is notable for being the first asteroid discovered to have a natural satellite, named Dactyl. This small moon, with a diameter of about 1.6 kilometers (1 mile), is composed of materials similar to those found on Ida. The formation of Dactyl is still a subject of scientific inquiry, with theories suggesting it may have either broken away from Ida or formed as a result of an impact. The Galileo spacecraft provided significant data about Ida and Dactyl during its flyby in 1993, which continues to inform research on asteroids and their potential implications for Earth.
243 Ida I Dactyl
FIELDS OF STUDY: Sub-planet Astronomy; Astrometry; Cosmology
ABSTRACT: (243) Ida I Dactyl (Dactyl) is the only moon of the asteroid 243 Ida. It was discovered in February 1994 when astronomers analyzed photographs taken by the Galileo spacecraft. This was the first known example of a natural satellite orbiting an asteroid.
243 Ida and Dactyl
243 Ida is an asteroid found in the region between Mars and Jupiter known as the asteroid belt. An asteroid is a rocky space object that is smaller than a planet and orbits the sun. Ida is a silicate (S-type) asteroid. S-type asteroids are fairly bright and are usually made of stone, nickel, and iron. First observed in 1884, Ida was the 243rd asteroid discovered. It was named after a mythical Greek nymph.
Ida is shaped irregularly. Instead of being spherical, the asteroid has two wide ends connected by a narrow waist. At its largest points, Ida’s diameter is roughly 31 kilometers (19.3 miles). Its surface is covered in many craters, suggesting huge numbers of collisions with smaller asteroids. From this, astronomers estimate that Ida is more than one billion years old. Ida has one small moon, Dactyl.
Dactyl’s History
Upon examination of photos of Ida, astronomers discovered that the asteroid has a small moon. It was the first time an asteroid was found with a natural satellite. The moon was named Dactyl, after the mythical Greek creatures said to be found on Mount Ida. It is composed of materials similar to Ida and has a diameter of about 1.6 kilometer (1 mile).
There are several theories about how Dactyl was formed. Ida’s gravitational field is too weak to have captured a separate object. Ida and Dactyl may have broken away from a larger object at the same time. Another possibility is that Dactyl was formed by an impact on Ida.
Galileo Mission
The Galileo spacecraft flew by Ida in 1993, providing the main data on the asteroid and its moon. Scientists continue to study this data to better understand asteroids. The age of such bodies gives insight into the origins of the solar system. Also, other asteroids may affect humans, both through the danger of an impact with Earth and as a potential source of mineral resources.
PRINCIPAL TERMS
- asteroid: a irregularly shaped space object that orbits the sun and is larger than one meter across but smaller than a planet.
- Ida: a heavily cratered asteroid that orbits the sun in the asteroid belt. It is likely at least a billion years old.
Bibliography
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