What is an asteroid? Ans in 100 words.
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Asteroids are minor planets, especially of theinner Solar System. Larger asteroids have also been called planetoids. These terms have historically been applied to any astronomical object orbiting the Sun that did not resemble a planet-like disc and was not observed to have characteristics of an activecomet such as a tail. As minor planets in the outer Solar System were discovered they were typically found to have volatile-rich surfaces similar to comets. As a result, they were often distinguished from objects found in the mainasteroid belt.[1] In this article, the term "asteroid" refers to the minor planets of the inner Solar System including those co-orbital with Jupiter.
There exist millions of asteroids, many thought to be the shattered remnants ofplanetesimals, bodies within the young Sun'ssolar nebula that never grew large enough to become planets.[2] The vast majority of known asteroids orbit within the main asteroid belt located between the orbits of Mars and Jupiter, or are co-orbital with Jupiter (theJupiter trojans). However, other orbital families exist with significant populations, including the near-Earth objects. Individual asteroids are classified by their characteristicspectra, with the majority falling into three main groups: C-type, M-type, and S-type. These were named after and are generally identified with carbon-rich, metallic, andsilicate (stony) compositions, respectively. The sizes of asteroids varies greatly; the largest, Ceres, is almost 1,000 km (625 mi) across.
Asteroids are differentiated from comets andmeteoroids. In the case of comets, the difference is one of composition: while asteroids are mainly composed of mineral and rock, comets are primarily composed of dust and ice. Furthermore, asteroids formed closer to the sun, preventing the development of cometary ice.[3] The difference between asteroids and meteoroids is mainly one of size: meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter.[4] Finally, meteoroids can be composed of either cometary or asteroidal materials.[5]
There exist millions of asteroids, many thought to be the shattered remnants ofplanetesimals, bodies within the young Sun'ssolar nebula that never grew large enough to become planets.[2] The vast majority of known asteroids orbit within the main asteroid belt located between the orbits of Mars and Jupiter, or are co-orbital with Jupiter (theJupiter trojans). However, other orbital families exist with significant populations, including the near-Earth objects. Individual asteroids are classified by their characteristicspectra, with the majority falling into three main groups: C-type, M-type, and S-type. These were named after and are generally identified with carbon-rich, metallic, andsilicate (stony) compositions, respectively. The sizes of asteroids varies greatly; the largest, Ceres, is almost 1,000 km (625 mi) across.
Asteroids are differentiated from comets andmeteoroids. In the case of comets, the difference is one of composition: while asteroids are mainly composed of mineral and rock, comets are primarily composed of dust and ice. Furthermore, asteroids formed closer to the sun, preventing the development of cometary ice.[3] The difference between asteroids and meteoroids is mainly one of size: meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter.[4] Finally, meteoroids can be composed of either cometary or asteroidal materials.[5]
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