Centaur (space science)
Centaurs are unique celestial objects located in the solar system, specifically found between the orbits of Jupiter and Neptune. Initially classified as asteroids, these objects exhibit characteristics of both asteroids and comets, leading to their designation as "centaurs," named after the half-horse, half-man creatures from Greek mythology. They are thought to originate from the Kuiper Belt, a region beyond Neptune populated by icy objects known as Kuiper Belt Objects (KBOs). Centaurs have unstable orbits that can be influenced by the gravitational pull of larger planets, resulting in their classification as temporary objects that might eventually be ejected from the solar system or transition into comets.
Research, particularly from NASA's Wide-field Infrared Survey Explorer (WISE), has indicated that many centaurs may be more comet-like than asteroid-like, with infrared data suggesting that a significant portion possesses darker, matte surfaces typical of comets. Notably, the discovery of rings around the centaur 10199 Chariklo in 2014 marked a significant finding in the study of these objects. Centaurs are valuable to scientists as they potentially hold clues about the early solar system, containing original materials from its formation. Overall, the study of centaurs provides important insights into the dynamics and evolution of celestial bodies within our solar system.
Centaur (space science)
FIELDS OF STUDY: Astronomy; Astrophysics; Sub-planet Astronomy
ABSTRACT: Centaurs are small objects in solar orbit between Jupiter and Neptune. Their orbits are unstable due to interactions with larger planets. Centaurs have characteristics of both comets and asteroids. Determining the true nature of centaurs and their origin will provide important information about the development of the early solar system.
Kuiper Belt Objects and Centaurs
The Kuiper Belt is a section of the solar system beyond Neptune’s orbit. It is populated with small icy objects called Kuiper Belt Objects (KBOs). The Kuiper Belt, also known as the Edgeworth-Kuiper Belt, was named after the men who first theorized its existence, Irish astronomer Kenneth Essex Edgeworth (1880–1972) and Dutch American astronomer Gerard Kuiper (1905–73).
KBOs are divided into classes based on their orbit. There are classical KBOs, resonance KBOs, and scattered KBOs or scattered disk objects (SDOs). When SDOs are affected by the forces of other celestial bodies, they can move into the area between Neptune and Jupiter. They are then called centaurs. Chiron, the first centaur object to be discovered, was detected in 1977. As of June 2022, researchers have found more than 1,400 centaurs and SDOs.
Characteristics of Centaurs
Centaurs were initially classified as asteroids. However, since Chiron was first seen, it has developed a coma. A coma is a cloud of debris. Therefore, it is now both a comet and an asteroid. This dual nature led scientists to dub the objects centaurs, after the half-horse, half-man creature in Greek mythology.
Scientists believe that centaurs were once caught by Neptune’s strong gravitational forces when they were knocked loose from their place in the Kuiper Belt. Their orbits are unstable because they cross the orbits of the larger planets. The unstable nature of their positions has led to the theory that their status as centaurs is temporary. Scientists think they will either be ejected from the solar system or become comets.
Centaur Research
In 2013, the National Aeronautics and Space Administration’s (NASA) Wide-field Infrared Survey Explorer (WISE) mission found information that led astronomers to believe centaurs may be more like comets than asteroids. Astronomers used WISE’s infrared data to examine centaurs. They also used knowledge about albedos. (The albedo is an object’s surface reflectivity.) They already knew that many of the objects were either blue-gray or red. The infrared data let them know whether a centaur was light and reflective or dark and matte. Asteroids tend to be brighter and more reflective, like the moon, while comets tend to be darker. The WISE study showed that nearly two-thirds of the centaurs studied are more likely to be comets. Additional observations conducted by WISE showed that at least some centaurs may be comets from beyond the solar system. These comets were pulled into orbit by the strong gravitational pull of the bigger planets.
In 2014, astronomers found two rings circling a large centaur known as 10199 Chariklo. It was the first time that astronomers saw rings around a small celestial object. Scientists are not sure what caused the rings, but data suggests they are composed of water ice.
Centaurs and Comets
The word comet brings to mind a bright object with a long glowing tail streaking across the sky. People may wonder how a comet can possibly be confused with a rocky asteroid. But a comet starts out as an irregularly shaped dark object. It only develops a tail as it nears the sun and its coma warms up and starts to blow away. Sunlight reflected off the coma forms the comet’s tail. The tail disappears as the comet begins to move away from the sun and the sun no longer shines on the debris. Without seeing the coma, it can be hard for scientists who are millions of kilometers away to tell if an object is a comet or an asteroid.
NASA’s WISE mission is an attempt to reveal the true nature of these and other objects from the far reaches of the solar system. The discovery that many or most centaurs may be comets does not change the importance of these dual-natured space objects. Scientists think that both comets and asteroids have original materials from the development of the solar system 4.6 billion years ago locked in their cores. Whether they are comets or asteroids, centaurs hold key information about the origins of the solar system.
Principal Terms
- asteroid: small, rocky space objects that orbit other larger celestial bodies such as the sun and planets. Asteroids are categorized in groups defined by their orbits.
- scattered disk objects: space bodies made of ice and rock with very eccentric, or flattened oval, orbits. They are found in the area beyond Neptune in the outer area of the solar system.
Bibliography
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