243 Ida

FIELDS OF STUDY: Astronomy; Observational Astronomy; Sub-planetary Astronomy

ABSTRACT: 243 Ida is a Koronis asteroid that orbits the sun between Mars and Jupiter. This asteroid and others in its family are irregularly shaped. The National Aeronautics and Space Administration (NASA) Galileo spacecraft observed 243 Ida in 1993. The spacecraft took images that showed 243 Ida has a natural satellite, named Dactyl. Studied frequently, 243 Ida has given scientists more information about asteroids. These objects can tell scientists about the formation of the early solar system and could have an impact on human life in the future.

243 Ida and Koronis Asteroids

243 Ida is an asteroid, or a small, rocky celestial body, that orbits the sun between Mars and Jupiter. This asteroid is a Koronis asteroid. The members of the Koronis family of asteroids are main-belt asteroids located between the orbits of Jupiter and Mars. These asteroids were once thought to be a product of a collision that happened very long ago between two large objects in the early solar system. Further study has revealed that this is most likely a more diverse group of objects from areas all over the solar system.

Koronis asteroids are irregularly shaped. They also rotate at similar speeds. In the past, scientists believed that asteroids spun at random speeds and that their rotations were determined by the force of previous collisions. However, in the 1990s and early 2000s, scientists learned that many of the Koronis family asteroids actually rotate at almost the same rate. They later found that light from the sun influences the rotation of these asteroids.

Ida is one of the more researched Koronis asteroids. Scientists have determined that it is 58 kilometers (36 miles) long and 23 kilometers (14 miles) wide. Its rotation is four hours and thirty-nine minutes.

Ida is an s-type asteroid, meaning that it is made of stone (silicate) and metals such as nickel and iron. Ida’s surface has many craters on it. This means that it has been involved in many collisions and that the surface is geologically old.

History of 243 Ida

In 1884 Austrian astronomer Johann Palisa (1848–1925) was searching for asteroids at the Vienna Observatory. On September 29, 1884, Palisa discovered 243 Ida. The asteroid was named by Moriz von Kuffner (1854–1939), an amateur astronomer from Vienna. The object was named after a nymph in Greek mythology who cared for the god Zeus when he was an infant.

Much new information about Ida was learned in the early 1990s when the spacecraft Galileo passed by it. Galileo was built to study Jupiter and its moons. The spacecraft observed Ida on its path to Jupiter. Galileo was closest to Ida on August 28, 1993. It traveled as close as 2,400 kilometers (1,500 miles) from the object. The spacecraft took images of the asteroid and transmitted them to Earth. In February 1994 Ann Harch—who was studying images from Galileo—noticed that Ida had a satellite. Scientists named the moon Dactyl, after a mythological creature that lived on Mount Ida.

Ida and Dactyl offered important information about asteroids. Scientists had long believed that some asteroids had their own moons, but they thought these moons were most likely uncommon. However, Ida was the second asteroid to be observed by a spacecraft and it had a moon. Scientists learned that asteroids with moons were probably more common than previously thought.

Studying 243 Ida and Asteroids

Scientists study 243 Ida and other asteroids for a number of reasons. One main reason is to learn about the early solar system. Many asteroids are leftover material from when the solar system formed. Their makeup can help scientists better understand how the solar system came into being.

Another reason scientists study asteroids is that their orbits can change. Their periphelions can be closer or farther away from Earth. Because of that, scientists need to track the orbits of 243 Ida and other asteroids to monitor whether these objects will ever come close to Earth. Asteroid impacts have happened on Earth’s surface in the past, and they will almost certainly occur again in the future. Understanding asteroids can help scientists predict if and when that might occur.

A third reason that scientists study Ida and other asteroids is that these objects could possibly supply humans with natural resources in the future. Many valuable resources could be mined from asteroids, so scientists are studying these objects to learn more about them. If humans use up resources on Earth, they may have to look to mining asteroids for valuable materials, such as metals.

PRINCIPAL TERMS

• aphelion: the point in an object’s orbital path that is farthest from the sun.
• asteroid: a small, rocky space object that orbits the sun or another celestial body.
• Koronis asteroid: a main-belt asteroid with an irregular shape that spins at about the same rate as the others in its family.
• main-belt asteroid: an asteroid that orbits the sun in the region between Mars and Jupiter.
• perihelion: the point in an object’s orbital path that is closest to the sun.
• s-type asteroid: fairly bright asteroids that are usually made of stone (silicate), nickel, and iron.

Bibliography

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"Images of Asteroids Ida & Dactyl." National Aeronautics and Space Administration. NASA, 22 Aug. 2005. Web. 26 Mar. 2015.

Nevres, M. Ozgur. "The First Moon in Orbit Around an Asteroid (243 Ida) Was Discovered on March 24, 1994." Our Planet, 26 Mar. 2022, ourplnt.com/first-moon-in-orbit-around-asteroid-243-ida/. Accessed 14 June 2022.

"New Spin on Asteroids." National Aeronautics and Space Administration. NASA, 21 Feb. 2011. Web. 26 Mar. 2015.

"243 Ida: Overview." National Aeronautics and Space Administration. NASA, 13 May 2014. Web. 26 Mar. 2015.