Asteroid

Asteroids

Greek, ά σ τ ε ρ ο ε ι δ ή ς

asteroeid's 'star-like, star-shaped'
from Ancient Greek ά σ τ ή ρ

astēr, star, planet

In the early second half of 19th century, the terms "asteroid" and "planet" are minor planets, especially those of the inner Solar System. The larger ones are referred to as planetoids (Greek, "planet-like"), any astronomical object orbiting the Sun that did not show the disc of a planet and was not observed to have the characteristics of an active comet. the minor planets of the inner Solar System including those co-orbital with Jupiter. There are millions of asteroids, many thought to be the shattered remnants of planetesimals, bodies within the young Sun's solar nebula that never grew large enough to become planets. The large majority of known asteroids orbit in the asteroid belt between the orbits of Mars and Jupiter, or are co-orbital with Jupiter near-Earth asteroids. Individual asteroids are classified by their characteristic spectra,

Tholen classification and SMASS classification proposed in 1984 by David J. Tholen, and was based on data collected from an eight-color asteroid survey performed in the 1980s. resulted in 14 asteroid categories. In 2002, the Small Main-Belt Asteroid Spectroscopic Survey resulted in a modified version of the Tholen taxonomy with 24 different types. Both systems have three broad categories of C, S, and X asteroids, where X consists of mostly metallic asteroids, such as the M-type. There are also several smaller classes.

the shapes and compositions of asteroids can be inferred from their light curves (their variation in brightness as they rotate) and their spectral properties, and asteroid sizes can be estimated by timing the lengths of star occulations (when an asteroid passes directly in front of a star the irregular, potato-like shapes of most asteroids, as did later images from the Voyager

Note: Text extracted from Wikipedia, Asteroid entry

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